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Abstract

Current obesity prevention strategies recommend increasing daily physical activity, assuming that increased activity will lead to corresponding increases in total energy expenditure and prevent or reverse energy imbalance and weight gain [1-3]. Such Additive total energy expenditure models are supported by exercise intervention and accelerometry studies reporting positive correlations between physical activity and total energy expenditure [4] but are challenged by ecological studies in humans and other species showing that more active populations do not have higher total energy expenditure [5-8]. Here we tested a Constrained total energy expenditure model, in which total energy expenditure increases with physical activity at low activity levels but plateaus at higher activity levels as the body adapts to maintain total energy expenditure within a narrow range. We compared total energy expenditure, measured using doubly labeled water, against physical activity, measured using accelerometry, for a large (n = 332) sample of adults living in five populations [9]. After adjusting for body size and composition, total energy expenditure was positively correlated with physical activity, but the relationship was markedly stronger over the lower range of physical activity. For subjects in the upper range of physical activity, total energy expenditure plateaued, supporting a Constrained total energy expenditure model. Body fat percentage and activity intensity appear to modulate the metabolic response to physical activity. Models of energy balance employed in public health [1-3] should be revised to better reflect the constrained nature of total energy expenditure and the complex effects of physical activity on metabolic physiology.

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... The "Constrained Energy Expenditure Model" suggests that TEE increases linearly with lower amounts of physical activity but plateaus with higher amounts of physical activity (10) and this has been observed in both animals (11)(12)(13)(14) and young adults (24-45yrs.; (15)). However, the mechanisms for energy constraint are unclear. ...
... This statistical approach was designed to replicate the strategy used by Pontzer and colleagues (15). We first examined the relationship of wear time and recruitment group on accelerometer-measured activity counts using linear regression and found significant associations (data not shown). ...
... The acute metabolic cost of physical activity is unquestionable; however, the impact of habitual levels of physical activity on TEE is less clear. The consensus view that increased physical activity leads to concomitant additive increases in TEE has been challenged (15,30). The Constrained Energy Expenditure model has been proposed as an alternative explanation to the previous Additive model. ...
Article
Purpose: To examine the shape of the relationship between physical activity (PA) and total energy expenditure (TEE) and to explore the role of energy balance status (negative, stable, positive) in influencing this association. Methods: Cross-sectional. Participants were 584 older adults (50-74 yrs.) participating in the Interactive Diet and Activity Tracking in AARP study. TEE was assessed by doubly labeled water and PA by accelerometer. The relationship between PA and TEE was assessed visually and using non-linear methods (restricted cubic splines). Percent weight change (>3%) over a six-month period was used as a proxy measurement of energy balance status. Results: TEE generally increased with increasing deciles of PA averaging 2354 (SD = 351) kcal/d in the bottom decile to 2693 (SD = 480) kcal/d in the top decile. Cubic spline models showed an approximate linear association between PA and TEE (linear relation p < 0.0001, curvature p = 0.920). Results were similar in subgroup analyses for individuals classified as stable or positive energy balance. For those in negative energy balance, TEE was generally flat with increasing deciles of PA averaging 2428 (SD = 285) kcal/d in the bottom decile to 2372 (SD = 560) kcal/d in the top decile. Conclusion: Energy balance status appears to play an important role in the relationship between PA and TEE. When in a positive energy balance, the relationship between TEE and PA was consistent with an additive model, however, when energy balance was negative, TEE appears to be consistent with a constrained model. These findings support PA for weight gain prevention by increasing TEE; however, the effect of PA on TEE during periods of weight loss may be limited. An adequately powered, prospective study is warranted to confirm these exploratory findings.
... As discussed in previous sections, body mass, sex, and age explain most of the variance in REE. PAEE, on the other hand, depends on the intensity and duration of movement (i.e., the level of physical activity) [12], which may vary greatly among subjects [49]. Consequently, PAEE appears to have larger variability than REE, even after adjusting for sex, age, fat-free mass, and fat mass [50]. ...
... In humans in energy balance consuming mixed diets, the thermic effect of food varies between 5% and 15% of TEE [54]. This is why the thermic effect of food is commonly considered as 10% of TEE in studies in free-living adults [6,12,49,50]. In this section, we will therefore focus on the determinants of PAEE. ...
... The level of physical activity can be measured with motion sensors that detect bodily accelerations. Thus, the level of physical activity is usually expressed in milligravity units (in 5-second epochs) or counts per minute [49,55]. Evidence shows a direct association between PAEE (adjusted for covariates) and the level of physical activity, at least from low-to-moderate levels of physical activity [49]. ...
Article
Humans acquire energy from the environment for survival. A central question for nutritional sciences is how much energy is required to sustain cellular work while maintaining an adequate body mass. Because human energy balance is not exempt from thermodynamic principles, the energy requirement can be approached from the energy expenditure. Conceptual and technological advances have allowed understanding of the physiological determinants of energy expenditure. Body mass, sex, and age are the main factors determining energy expenditure. These factors constitute the basis for predictive equations for resting (REE) and total (TEE) energy expenditure in healthy adults. These equations yield predictions that differ up to ~400 kcal/d for REE and ~550 kcal/d for TEE. Identifying additional factors accounting for such variability and the most valid equations appears relevant. This review used novel approaches based on mathematical modeling of REE and analyses of the data from which REE predictive equations were generated. As for TEE, R2 and SE were considered because only a few predictive equations are available. From these analyses, Oxford's and Plucker's equations appear valid for predicting REE and TEE in adults, respectively.
... Thus, the primary purpose of this study was to assess the feasibility of performing HIIT during pregnancy and the maternal glycemic response to an acute bout of HIIT compared with the traditional form of prenatal exercise, MICT. Fundamental aspects of physical performance, such as nutritional intake, sleep quality/duration, and physical activity (Charest & Grandner, 2020;Lee et al., 2017), will also be examined to assess the potential differences in exercise performance and identify any postintervention compensatory behaviors (e.g., increased sedentary time and caloric intake) which could undermine the health benefits achieved with MICT/ HIIT (Pontzer et al., 2016). ...
... Traditionally, the strenuous nature of vigorous-intensity exercise has led to concerns that the benefits of these activities, such as HIIT, would be counterbalanced by a reduction in overall physical activity levels outside of the exercise session due to an increase in perceived fatigue (Pontzer et al., 2016). Through objective measures of freeliving physical activity and self-reported dietary records, we were able to examine whether an acute bout of HIIT during pregnancy resulted in compensatory behaviors. ...
... Through objective measures of freeliving physical activity and self-reported dietary records, we were able to examine whether an acute bout of HIIT during pregnancy resulted in compensatory behaviors. Compensatory behaviors are concerning as they may undermine the health benefits achieved through physical activity (Pontzer et al., 2016). Despite the significantly greater session and exercise rating of perceived exertion during HIIT, objectively monitored physical activity patterns (i.e., sedentary, light, and moderate-to-vigorous intensity physical activity) were not different on the day prior to, of, or following HIIT compared with MICT. ...
Article
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The present study investigated the glycemic response to an acute high-intensity interval training (HIIT) session (10 one-minute intervals ≥90% HRmax interspersed with one-minute of active recovery) versus a moderate-intensity continuous training (MICT) session (30 min at 64%-76% HRmax ) during pregnancy. Twenty-four normoglycemic females with a singleton pregnancy (27.8 ± 4.7 weeks of gestation, 31.5 ± 4.1 years of age, body mass index: 25.2 ± 11.3) participated in a randomized crossover design study. A flash glucose monitor and accelerometer were worn continuously for 7 days recording glycemic response, physical activity, and sleep. Nutritional intake and enjoyment of the exercise were self-reported. Average heart rate during exercise was higher for HIIT (82 ± 4% HRmax ) compared with MICT (74 ± 4% HRmax ; p < 0.001) and participants achieved a peak heart rate of 92 ± 3% during HIIT (range 85%-97% HRmax ) compared with 81 ± 4% during MICT (p < 0.001). The change in glucose values from pre-to-postexercise were not different between conditions (HIIT: -0.62 ± 1.00 mmol/L; MICT: -0.81 ± 1.05 mmol/L; p = 0.300) with the exception that fewer individuals experienced postexercise hypoglycemia immediately following HIIT compared with MICT (8% versus 33% respectively; p = 0.041). Other glucose variables was not different between exercise protocols. Physical activity (p = 0.07) and caloric intake did not differ (p = 0.10). The majority of participants preferred HIIT (87.5%) and had greater perceived enjoyment compared to MICT (HIIT: 7.8 ± 1.5; MICT: 6.6 ± 2.0; p = 0.015). Sleep duration was 52 ± 73 min longer after participating in HIIT compared with the night prior (main effect for time p = 0.017); no significant changes for MICT. Overall, an acute session of HIIT appears to be well tolerated and demonstrates no adverse effects on maternal glycemic response.
... In this new proposal, the energy expenditure that is not derived from physical activity dynamically adapts to variations in physical activity to maintain the TEE within a homeostatic range. This model has already been tested a few times in different populations (Pontzer et al., 2016;Willis et al., 2022). ...
... This hypothesis was presented and tested by Pontzer et al. (2016) in which 332 individuals of both sexes, from five different countries and different BMI categories, to identify the suitability for the nonlinear model. As in the study by Pontzer et al. (2016), the present investigation found that before the change point identified in the analyzes between the Model 5 adjusted-TEE relationship and MET.h/d, the effect of a physical activity marker on TEE seems to be underestimated in linear models, and subsequently theoretically compensated for higher PAL, in which it reaches a possible plateau in this relationship. ...
... This hypothesis was presented and tested by Pontzer et al. (2016) in which 332 individuals of both sexes, from five different countries and different BMI categories, to identify the suitability for the nonlinear model. As in the study by Pontzer et al. (2016), the present investigation found that before the change point identified in the analyzes between the Model 5 adjusted-TEE relationship and MET.h/d, the effect of a physical activity marker on TEE seems to be underestimated in linear models, and subsequently theoretically compensated for higher PAL, in which it reaches a possible plateau in this relationship. This adaptation of the TEE to higher levels of physical activity, described in the non-linear model, can be explained by evolutionary mechanisms of the species, with the effects of availability of energy from food and energy expenditure for maintaining life, reduction of somatic repair, growth retardation and decreased activity and release of reproductive hormones in response to higher levels of physical activity (Deerenberg & Overkamp, 1999;Perrigo, 1987;Perrigo & Bronson, 1983;Westerterp, 2010;Wiersma & Verhulst, 2005). ...
Article
Objective: This study aimed to describe how strong is the relationship between TEE and PAL in women living in an impoverished Brazilian urban area. Methods: Anthropometric, hormonal (insulin, TSH, FT4 , and FT3 ), body composition (deuterium), TEE (doubly labeled water) and PAL (metabolic equivalent task [MET]-7-day triaxial accelerometer, ActivPAL®) data were collected from 55 women (mean age: 31y, mean BMI: 27.4 kg/m2 ). Adjusted-TEE models were calculated incorporating the residuals of anthropometric, hormonal, and body composition variables in the TEE, to assess the relation between MET and adjusted-TEE, through three different analyzes: linear regression, nonlinear regression and change-point regression. Results: Most participants (89.1%, n = 49) were classified as low-active. There was no association between crude TEE and MET.h/d (R2 = 0.05; p = 0.09). There was a positive, although weak, linear relationship between adjusted-TEE and MET.h/d (β = 2705.26 kcal; 95% CI: 436.25; 4974.27; adj-R2 = 0.08). A change point of this relationship was identified in the MET.h/d value of 1.53 (SD = 0.02; adj-R2 = 0.13). The association between adjusted-TEE and MET.h/d before the change point (β = 5101.46 kcal; 95%CI: 978.84; 9224.08; adj-R2 = 0.11) was stronger than the association in the full linear model, nevertheless, it was still weak. This association stop existing when it is assessed in individuals after the change point (β = -6609.92 kcal; 95%CI: -16773.24; 3553.40; adj-R2 = 0.08). Conclusions: These results suggest that the relationship between TEE and PAL is weak and it is not completely linear in women living in an impoverished Brazilian urban area.
... Physical activity is a lifestyle factor with well-documented positive health effects; in mice, exercise training has been shown to increase energy expenditure, offsetting the weight-gain induced by HFD (Sasaki et al. 2014). Physical activity-related energy expenditure (AEE), a measure of physical activity's contribution to metabolic rate, can be calculated in mice using calorimetry data (Hills et al. 2014;Pontzer et al. 2016;Van Klinken et al. 2012). In addition to affecting energy expenditure, exercise/physical activity has also shown associations with gene promoterspecific DNA methylation in mice (Kanzleiter et al. 2015;King-Himmelreich et al. 2016;Nguyen et al. 2016), suggesting that physical activity may also offset the epigenetic effects of HFD. ...
... following formula: AEE = 0.9(TEE) -RMR(Hills et al. 2014;Pontzer et al. 2016; Van Klinken et al. 2012). The 0.9 multiplier was based on the thermic effect of food (TEF), which was assumed to be ~10% of TEE(Hills et al. 2014). ...
Thesis
Increasing evidence supports the developmental origins of health and disease (DOHaD) hypothesis, which posits that exposure to environmental factors (e.g. diet, chemicals, stress etc.) during sensitive periods of life (e.g. pre-conception, gestation, infancy, adolescence) alters disease susceptibility later in life by influencing developmental plasticity. As support for DOHaD accumulates, it has been proposed that developmental exposures alter later-life gene regulation and subsequent phenotype through changes in heritable epigenetic marks – e.g. DNA methylation. Both biological aging and environmental exposures are associated with changes in DNA methylation, and it has been shown that developmental exposures can alter the rate of epigenetic aging. Based on these existing data, we defined a new term – environmental deflection – that refers to an environment- or toxicant-mediated shift away from the baseline rate of epigenetic aging within an organism. For this project, longitudinal animal model and human cohort studies were used to investigate whether developmental exposure to specific environmental factors – bisphenol A (BPA), Western high-fat diet (WHFD), and physical activity – would lead to environmental deflection of the aging epigenome. In the animal model study, matched blood and tail samples were collected from congenic a/a Agouti mice perinatally exposed to BPA (50 µg/kg diet) and/or WHFD. Linear mixed effects models were used to test for environmental deflection of epigenetic aging by dietary exposures. In the same mice, we used two next-generation sequencing methods – enhanced reduced representation bisulfite sequencing (ERRBS) and hydroxymethylated DNA immunoprecipitation sequencing (HMeDIP-seq) – to determine the contributions of 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) to the aging epigenome. In the Healthy Families Project, a human cohort, we investigated the effects of physical activity and diet quality on age-related methylation in longitudinal blood samples. DNA methylation was measured at obesity-related genes in matched neonatal bloodspot and childhood blood samples (12-24 months old, 3-5 years old, 10-12 years old). In an effort to test the utility of neonatal blood DNA methylation as a biomarker of obesity risk during childhood, we also investigated whether childhood obesity likelihood was associated with neonatal and/or childhood DNA methylation at a number of obesity-related genes. In both the mouse and human studies, we showed significant, gene-specific age-related DNA methylation. In mice, WHFD, but not BPA exposure, deflected age-related Esr1 methylation rates away from Control baseline. In the mouse blood sequencing data, we showed a locus-specific contribution of 5-hmC to age-related DNA methylation patterns in mice, and also demonstrated significant effects of BPA exposure on DNA hydroxymethylation in the gene bodies of imprinted loci. In the human cohort, environmental deflection modeling was limited by sample size, but there was some indication of deflection by childhood BMI z-score and physical activity levels. Neonatal bloodspot LINE-1 DNA methylation was significantly associated with obesity likelihood in preschool children, and childhood PPARA was also negatively associated with body mass index z-score. In this dissertation, we showed that both altered diet and physical activity have the potential to alter rates of epigenetic aging. Separately, we found that developmental BPA exposure stably alters DNA hydroxymethylation at murine imprinted genes, and that human neonatal bloodspot DNA methylation may be a useful biomarker for estimating childhood obesity risk. These results emphasize the importance of longitudinal study design in toxicoepigenetics research, and suggest that environmental factors play a key role in the developmental origins of adult disease.
... Ordinary Least Squares simple regressions of EE variables on anthropometric measures were computed. Following this, multiple stepwise linear regressions via forward selection were used (with a selection criterion to enter of p < 0.05), including body mass as a covariate (Kleiber, 1947;Pontzer et al., 2016; White & Seymour, 2003), to investigate the relationship between age, height, BIL and FL, and the GrossCOT of simulated walking and gathering activities. To test if energy expenditure was the same for girls and boys with the same body mass, the slopes and intercepts of the simple models were compared with an ANOVA test. ...
... In consonance with previous studies (Brooks et al., 2005;Froehle et al., 2013b;Passmore & Durnin, 1955;Pontzer et al., 2016;Steudel-Numbers, 1996Steudel-Numbers & Tilkens, 2004), our results show the effect of body mass on locomotion. In our experimental study, both activities are highly correlated with body mass because gathering includes locomotion; in addition, locomotion activities are the most common form of physical activity in general (Brooks et al., 2005;Passmore & Durnin, 1955) for hunter-gatherer children (Hagino & Yamauchi, 2014). ...
Article
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In some small-scale societies, a sexual division of labor is common. For subadult hunter-gatherers, the onset of this division dates to middle childhood and the start of puberty; however, there is apparently no physiological explanation for this timing. The present study uses an experimental approach to evaluate possible energetic differences by sex in gathering-related activities. The energetic cost of gathering-related activities was measured in a sample of 42 subjects of both sexes aged between 8 and 14 years. Body mass and other anthropometric variables were also recorded. Our results show that the energetic differences in the simulated gathering activities depend only on body mass. Both sexes expend a similar amount of energy during locomotion activities related to gathering. Discarding the energetic factor, the sexual division of tasks may be explained as an adaptation to acquire the skills needed to undertake the complex activities required during adulthood as early as possible. Carrying out gathering activities during childhood and adolescence could be favored by the growth and development cycles of Homo sapiens. Moreover, if most of the energetic costs of gathering activities depend on body mass, the delayed growth in humans relative to other primates allows subadults to practice these tasks for longer periods, and to become better at performing them. In fact, this strategy could enable them to acquire adults’ complex skills at a low energetic cost that can be easily subsidized by other members of the group.
... The buffering of metabolic cost coupled with an increase in heat production reflected in our findings align with the constrained total energy model, first proposed by Pontzer et al. (2016). This model suggests that habitual elevated physical activity levels will provoke a physiological response reducing the metabolic cost of different total energy expenditure components, keeping total energy expenditure within a narrow range. ...
Article
Objectives We investigated seasonal changes in brown adipose tissue (BAT) activation and metabolism in a temperate-climate Albany, NY population. Methods Data were collected among 58 participants (21 males, 37 females, ages: 18–51) in the summer and 59 participants (23 males, 36 females, ages: 18–63) in the winter in Albany, New York. BAT activity was inferred by comparing metabolic rate, heat dissipation in the supraclavicular area, and respiratory quotient at room temperature and cold exposure. Seasonal variation in BAT was determined by comparing these measurements from summer and winter. Results At mild cold exposure, heat dissipation of the supraclavicular area was significantly greater in the winter compared to summer (p < .001); however, no significant differences were found between seasons in metabolic rate measurements. This suggests BAT activation may be metabolically more efficient in the winter, due to prolonged lower seasonal temperatures relative to summer. Respiratory quotient significantly increased upon mild cold exposure in the winter compared to summer (p < .001). While carbohydrate utilization increased in the winter, fat remained the primary metabolic substrate for BAT activity across both seasons. Conclusion The seasonal variations in the effects of nonshivering thermogenesis on metabolic rate and substrate metabolism suggest a buffering of energy expenditure and an increased use of glucose as fuel by BAT as a result of acclimatization to cold in the winter. These findings point towards a potential role of BAT in human whole-body mediated glucose disposal and cold adaptation.
... In addition, total energy expenditure does not increase with exercise in a dose-dependent manner. Instead, there is a threshold above which an increase in exercise intensity or duration decreases energy expenditure by other organ systems in such a way that total energy expenditure plateaus [34,35]. Evolutionarily, such a constrained energy expenditure model would be advantageous. ...
Article
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Background/aims: Epigenetic regulation is considered the main molecular mechanism underlying the developmental origin of health and disease's (DOHAD) hypothesis. Previous studies that have investigated the role of paternal exercise on the metabolic health of the offspring did not control for the amount and intensity of the training or possible effects of adaptation to exercise and produced conflicting results regarding the benefits of parental exercise to the next generation. We employed a precisely regulated exercise regimen to study the transgenerational inheritance of improved metabolic health. Methods: We subjected male mice to a well-controlled exercise -training program to investigate the effects of paternal exercise on glucose tolerance and insulin sensitivity in their adult progeny. To investigate the molecular mechanisms of epigenetic inheritance, we determined chromatin markers in the skeletal muscle of the offspring and the paternal sperm. Results: Offspring of trained male mice exhibited improved glucose homeostasis and insulin sensitivity. Paternal exercise modulated the DNA methylation profile of PI3Kca and the imprinted H19/Igf2 locus at specific differentially methylated regions (DMRs) in the skeletal muscle of the offspring, which affected their gene expression. Remarkably, a similar DNA methylation profile at the PI3Kca, H19, and Igf2 genes was present in the progenitor sperm indicating that exercise-induced epigenetic changes that occurred during germ cell development contributed to transgenerational transmission. Conclusion: Paternal exercise might be considered as a strategy that could promote metabolic health in the offspring as the benefits can be inherited transgenerationally.
... A greater NetC w/kg therefore represents a potential target for morbid obesity management through the daily total energy expenditure increase (TEE), especially in sedentary people with obesity who are in the so-called "unregulated zone", in which appetite and food intake are not affected by TEE; thus, food intake drives body weight gain [44]. Although increasing physical activity using walking and its associated higher NetC w/kg could be useful to shift individuals with obesity into the "regulated zone", in which appetite and food intake are affected by physical activity [44], the role of the latter in energy balance and weight loss remains controversial [44][45][46]. Nevertheless, decreasing the greater NetC w/kg in adults with obesity may be beneficial to increase non-exercise activity thermogenesis (NEAT) [11], and thus, light physical activity energy expenditure (1.6-2.9 metabolic equivalents; METs), which is inversely related to sedentary time [47] and has complementary effects to improve health [48]. ...
Article
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Higher mass-normalized net energy cost of walking (NetCw/kg) and mechanical pendular recovery are observed in obese compared to lean adults. This study aimed to investigate the effect of different classes of obesity on the energetics and mechanics of walking and to explore the relationships between body mass, NetCw/kg and gait mechanics by using principal component analysis (PCA). NetCw/kg and gait mechanics were computed in severely obese (SOG; n = 18, BMI = 40.1 ± 4.4 kg·m−2), moderately obese (MOG; n = 17, BMI = 32.2 ± 1.5 kg·m−2) and normal-weight (NWG; n = 13, BMI = 22.0 ± 1.5 kg·m−2) adults during five walking trials (0.56, 0.83, 1.11, 1.39, 1.67 m·s−1) on an instrumented treadmill. NetCw/kg was significantly higher in SOG compared to NWG (p = 0.019), with no significant difference between SOG and MOG (p = 0.14), nor between MOG and NWG (p = 0.27). Recovery was significantly higher in SOG than in NWG (p = 0.028), with no significant difference between SOG and MOG (p = 0.13), nor between MOG and NWG (p = 0.35). PCA models explained between 17.0% and 44.2% of the data variance. This study showed that: (1) obesity class influences the gait energetics and mechanics; (2) PCA was able to identify two components, showing that the obesity class is associated with lower walking efficiency and better pendulum-like characteristics.
... A greater NetC w/kg therefore represents a potential target for morbid obesity management through the daily total energy expenditure increase (TEE), especially in sedentary people with obesity who are in the so-called "unregulated zone", in which appetite and food intake are not affected by TEE; thus, food intake drives body weight gain [44]. Although increasing physical activity using walking and its associated higher NetC w/kg could be useful to shift individuals with obesity into the "regulated zone", in which appetite and food intake are affected by physical activity [44], the role of the latter in energy balance and weight loss remains controversial [44][45][46]. Nevertheless, decreasing the greater NetC w/kg in adults with obesity may be beneficial to increase non-exercise activity thermogenesis (NEAT) [11], and thus, light physical activity energy expenditure (1.6-2.9 metabolic equivalents; METs), which is inversely related to sedentary time [47] and has complementary effects to improve health [48]. ...
Article
Full-text available
Higher mass-normalized net energy cost of walking (NetCw/kg) and mechanical pendular recovery are observed in obese compared to lean adults. This study aimed to investigate the effect of different classes of obesity on the energetics and mechanics of walking and to explore the relationships between body mass, NetCw/kg and gait mechanics by using principal component analysis (PCA). NetCw/kg and gait mechanics were computed in severely obese (SOG; n = 18, BMI = 40.1 ± 4.4 kg·m−2), moderately obese (MOG; n = 17, BMI = 32.2 ± 1.5 kg·m−2) and normal-weight (NWG; n = 13, BMI = 22.0 ± 1.5 kg·m−2) adults during five walking trials (0.56, 0.83, 1.11, 1.39, 1.67 m·s−1) on an instrumented treadmill. NetCw/kg was significantly higher in SOG compared to NWG (p = 0.019), with no significant difference between SOG and MOG (p = 0.14), nor between MOG and NWG (p = 0.27). Recovery was significantly higher in SOG than in NWG (p = 0.028), with no significant difference between SOG and MOG (p = 0.13), nor between MOG and NWG (p = 0.35). PCA models explained between 17.0% and 44.2% of the data variance. This study showed that: (1) obesity class influences the gait energetics and mechanics; (2) PCA was able to identify two components, showing that the obesity class is associated with lower walking efficiency and better pendulum-like characteristics.
... Reduction in physical activity and sedentary lifestyle were positively associated with energy balance in self-quarantine participants as stated by Zachary et al, 2021 (30). Although the links between physical activity, and energy expenditure and obesity development are unclear (31,32). It is possible at least in theory that reduced physical activity and snacking could offset the reduced intake from FFRs and FSRs. ...
Article
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Background: The United Kingdom (UK) implemented several national lockdowns during the coronavirus pandemic during which restaurants were closed and people were advised to stay at home if possible. These restrictions were eased and reapplied multiple times between March 2020 and May 2021. The change in restaurant access and prolonged restriction of activity may have an impact on body weight. Aim: The aim of this study was to examine the impact of multiple lockdowns on body mass index (BMI) change from pre-pandemic till during the third lockdown and on the use of different types of food outlets and their association with BMI change. Materials and method: Surveys of usage of different types of food outlets were distributed online before the lockdown between 06 January and 12 December 2019 and during the third national lockdown between 29 March and 25 April 2021. The food outlet usage surveys were filled out for seven consecutive days. Self-reported BMI was reported before the pandemic and during the third phase of the lockdown. The total number of individuals who started the study before the pandemic was 681, and 60 participants completed the surveys during the third phase of lockdown. Results: For the 60 participants in both surveys mean BMI was significantly higher during the third lockdown (28.6 ± 5.9 kg.m2) in comparison with the mean BMI before the pandemic 2019 (28.0 ± 5.5 kg.m2) (paired T = 3.09, p < 0.003). There was a significant positive association between BMI change, total number of days spent in lockdown (β = 0.05, p < 0.01, R 2 = 9.99), and age (β = 0.06, p < 0.007, R 2 = 11.8). There was no significant association between change in BMI and change in the frequency of using fast food restaurants (FFRs), full-service restaurants (FSRs), and delivery and takeaways. Conclusion: BMI was increased significantly during the lockdown in comparison with prior to the pandemic. Individuals gained more weight the longer they stayed at home during lockdowns, and physical activity was reduced to approximately half. However, the BMI change was not related to the change in use of different types of food outlets. This pattern does not support the widespread belief that visiting restaurants or using delivery and takeaway services has a significant impact on body weight.
... Previous studies suggested that, compared to the overweight or obese sedentary populations, active lean individuals might benefit more from IER strategies due to their different metabolic statuses [11]. At the same time, the recently proposed "constrained energy expenditure model" and the experimental basis of this model in humans included cross-sectional data might provide alternative explanations, which is that the daily energy expenditure would be regulated and that free-living daily energy expenditure adjusted for body composition is relatively constant [42][43][44]. Similarly, it also could not be proved that there is no difference in metabolic adaption between IERG and CERG. ...
Article
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Objective: To compare the effects of continuous energy restriction (CER) and intermittent energy restriction (IER) in bodyweight loss plan in sedentary individuals with normal bodyweight and explore the influence factors of effect and individual retention. Methods: 26 participants were recruited in this randomized controlled and double-blinded trial and allocated to CER and IER groups. Bodyweight (BW), body mass index (BMI), and resting metabolic rate (RMR) would be collected before and after a 4-week (28 days) plan which included energy restriction (CER or IER) and moderate-intensity exercise. Daily intake of three major nutrients (protein, carbohydrate, fat) and calories were recorded. Results: A significant decrease in BW and BMI were reported within each group. No statistically significant difference in the change of RMR in CERG. No statistically significant difference was reported in the effect between groups, neither as well the intake of total calories, three major nutrients, and individual plan retention. The influence factors of IER and CER are different. Conclusion: Both CER and IER are effective and safe energy restriction strategies in the short term. Daily energy intake and physical exercise are important to both IER and CER.
... One issue that requires further study is evidence from cross-sectional studies that total daily energy expenditure (DEE) relative to lean body mass is not higher in physically active non-Western populations, including Hadza huntergatherers, than in sedentary Westerners (42). This observation has led to the hypothesis that individuals compensate for higher levels of PA by lowering their BMR (62). The metabolic mechanisms underlying this hypothesized adaptation, however, have yet to be identified, and it is unknown whether evolutionarily normal levels of PA lead to lower BMRs or if sedentary individuals have disregulated BMRs. ...
Article
The proximate mechanisms by which physical activity (PA) slows senescence and decreases morbidity and mortality have been extensively documented. However, we lack an ultimate, evolutionary explanation for why lifelong PA, particularly during middle and older age, promotes health. As the growing worldwide epidemic of physical inactivity accelerates the prevalence of noncommunicable diseases among aging populations, integrating evolutionary and biomedical perspectives can foster new insights into how and why lifelong PA helps preserve health and extend lifespans. Building on previous life-history research, we assess the evidence that humans were selected not just to live several decades after they cease reproducing but also to be moderately physically active during those postreproductive years. We next review the longstanding hypothesis that PA promotes health by allocating energy away from potentially harmful overinvestments in fat storage and reproductive tissues and propose the novel hypothesis that PA also stimulates energy allocation toward repair and maintenance processes. We hypothesize that selection in humans for lifelong PA, including during postreproductive years to provision offspring, promoted selection for both energy allocation pathways which synergistically slow senescence and reduce vulnerability to many forms of chronic diseases. As a result, extended human healthspans and lifespans are both a cause and an effect of habitual PA, helping explain why lack of lifelong PA in humans can increase disease risk and reduce longevity.
... 20,21 Recent δ 18 O measurements of body fluids have been conducted almost exclusively with urine, and occasionally with either plasma or serum. 22 ...
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Rationale: Blood water oxygen isotope compositions can provide valuable insights into physiological processes and ecological patterns. While blood samples are commonly drawn for medical or scientific purposes, blood fractions are infrequently measured for oxygen isotopic compositions (δ18 O) because such measurements are time consuming and expensive. Methods: We sampled blood from sheep, goats, and iguanas raised in field and animal laboratories into serum, EDTA, heparin, and uncoated plastic vials commonly used in medical and scientific research, then separated red blood cell (RBC) and plasma or serum blood fractions. These were injected into helium-flushed Exetainer tubes where they naturally outgassed endogenous CO2 (goat blood), or into He- and CO2 -flushed tubes (iguana blood). The CO2 gas was sampled on a GasBench II system, and δ18 O was measured by an isotope ratio mass spectrometer (IRMS). Results: Repeated δ18 O measurements were stable over multiple days. The addition of desiccated blood solids to water standards had little impact on their δ18 O measurements, suggesting that organic molecular constituents within blood serum and plasma do not interfere with blood water δ18 O values. We observed slight but statistically significant δ18 O offsets between plasma, serum and RBC fractions. Mass-dependent body water turnover times for iguanas were derived from the data. Conclusions: We demonstrate that a simple blood-CO2 equilibration method using the GasBench can quickly, reliably and accurately characterize water δ18 O in the plasma, RBC, and whole blood fractions of mammalian and reptilian blood samples (precision ≤ 0.1 ‰). This method will expand the application of blood stable isotope analysis in physiological and medical research.
... BMR has the strongest effect on DEE under conditions of thermoneutrality (thus, it is particularly recommended when one examines the effect of BMR on an analyzed trait). Interestingly, in humans, the link between physical activity and DEE is significant for low intensity activities but disappears when DEE is high (Pontzer et al. 2016), though not because of a substitution for thermoregulation but rather due to changes in other components of the energy budget (Pontzer 2015). Thus, the SPA of laboratory mice can be a valid model of at least relatively sedentary (i.e., Western) human populations but only in the TNZ where there is clear link between SPA and DEE. ...
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The basal metabolic rate (BMR) accounts for 60–70% of the daily energy expenditure (DEE) in sedentary humans and at least 50% of the DEE in laboratory mice in the thermoneutral zone. Surprisingly, however, the significance of the variation in the BMR is largely overlooked in translational research using such indices as physical activity level (PAL), i.e., the ratio of DEE/BMR. In particular, it is unclear whether emulation of human PAL in mouse models should be carried out within or below the thermoneutral zone. It is also unclear whether physical activity within the thermoneutral zone is limited by the capacity to dissipate heat generated by exercise and obligatory metabolic processes contributing to BMR. We measured PAL and spontaneous physical activity (SPA) in laboratory mice from two lines, divergently selected towards either high or low level of BMR, and acclimated to 30 °C (i.e., the thermoneutral zone), 23 or 4 °C. The mean PAL did not differ between both lines in the mice acclimated to 30 °C but became significantly higher in the low BMR mouse line at the lower ambient temperatures. Acclimation to 30 °C reduced the mean locomotor activity but did not affect the significant difference observed between the selected lines. We conclude that carrying out experiments within the thermoneutral zone can increase the consistency of translational studies aimed at the emulation of human energetics, without affecting the variation in physical activity correlated with BMR.
... Thermogenesis makes up about 10 % of total energy expenditure which plateaus above moderate physical activity levels [38]. Diet-induced thermogenesis is determined by the diet consumed. ...
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Global warming and the rising prevalence of obesity are well described challenges of current mankind. Most recently, the COVID-19 pandemic arose as a new challenge. We here attempt to delineate their relationship with each other from our perspective. Global greenhouse gas emissions from the burning of fossil fuels have exponentially increased since 1950. The main contributors to such greenhouse gas emissions are manufacturing and construction, transport, residential, commercial, agriculture, and land use change and forestry, combined with an increasing global population growth from 1 billion in 1800 to 7.8 billion in 2020 along with rising obesity rates since the 1980s. The current Covid-19 pandemic has caused some decline in greenhouse gas emissions by limiting mobility globally via repetitive lockdowns. Following multiple lockdowns, there was further increase in obesity in wealthier populations, malnutrition from hunger in poor populations and death from severe infection with Covid-19 and its virus variants. There is a bidirectional relationship between adiposity and global warming. With rising atmospheric air temperatures, people typically will have less adaptive thermogenesis and become less physically active, while they are producing a higher carbon footprint. To reduce obesity rates, one should be willing to learn more about the environmental impact, how to minimize consumption of energy generating carbon dioxide and other greenhouse gas emissions, and to reduce food waste. Diets lower in meat such as a Mediterranean diet, have been estimated to reduce greenhouse gas emissions by 72%, land use by 58%, and energy consumption by 52%.
... And for humans specifically, lab-based studies also indicate an unclear role for NEAT. When a reduction in NEAT is recorded, it can rarely account for a substantial proportion of the observed energy compensation (Colley et al. 2005;Pontzer 2015;Pontzer et al. 2016). In contrast, the few experiments of NEAT in animals, all on mice, provide clearer evidence of its substantive role in energy compensation. ...
Article
The received wisdom on how activity affects energy expenditure is that the more activity is undertaken, the more calories will have been burned by the end of the day. Yet traditional hunter-gatherers, who lead physically hard lives, burn no more calories each day than Western populations living in labor-saving environments. Indeed, there is now a wealth of data, both for humans and other animals, demonstrating that long-term lifestyle changes involving increases in exercise or other physical activities do not result in commensurate increases in daily energy expenditure (DEE). This is because humans and other animals exhibit a degree of energy compensation at the organismal level, ameliorating some of the increases in DEE that would occur from the increased activity by decreasing the energy expended on other biological processes. And energy compensation can be sizable, reaching many hundreds of calories in humans. But the processes that are downregulated in the long-term to achieve energy compensation are far from clear, particularly in humans-we do not know how energy compensation is achieved. My review here of the literature on relevant exercise intervention studies, for both humans and other species, indicates conflict regarding the role, if any, of basal metabolic rate (BMR) or low-level activity such as fidgeting play, particularly once changes in body composition are factored out. In situations where BMR and low-level activity are not major components of energy compensation, what then drives it? I discuss how changes in mitochondrial efficiency and changes in circadian fluctuations in BMR may contribute to our understanding of energy management. Currently unexplored, these mechanisms and others may provide important insights into the mystery of how energy compensation is achieved.
... Concerning extinct human species, aside from this fragile equilibrium between caloric intake and energy expenditure (Amen-Ra 2006), researchers have proposed that thickened cortical bones and pronounced areas of muscle attachment reflect high activity levels (Shaw and Stock 2013), which could entail higher energy requirements than modern humans (Froehle and Churchill 2009;Sorensen and Leonard 2001; but see Pontzer et al. 2016). On this basis, Trinkaus stated that "subsistence efficiency of these archaic humans was markedly less than that of more recent humans" (1986:206), a widely held idea in the paleoanthropological literature (but see Sorensen and Leonard 2001). ...
... The elevated energy expenditure associated with the low-economy high-energy turnover approach may bring costs, however. Recent work has identified preliminary evidence suggestive of an apparent limit to daily energy expenditure, with daily energy expenditure being homeostatically maintained within a narrow evolved physiological range (Pontzer, 2015a, b;Pontzer et al., 2016). The constrained total energy expenditure model contends that the addition of further physical activity, with associated additional energy costs, to individuals who are already moderately active does not result in increased total energy expenditure. ...
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Objective A suite of adaptations facilitating endurance running (ER) evolved within the hominin lineage. This may have improved our ability to reach scavenging sites before competitors, or to hunt prey over long distances. Running economy (RE) is a key determinant of endurance running performance, and depends largely on the magnitude of force required to support body mass. However, numerous environmental factors influence body mass, thereby significantly affecting RE. This study tested the hypothesis that alternative metabolic strategies may have emerged to enable ER in individuals with larger body mass and poor RE. Methods A cohort of male (n = 25) and female (n = 19) ultra-endurance runners completed submaximal and exhaustive treadmill protocols to determine RE, and V̇O 2Max . Results Body mass was positively associated with sub-maximal oxygen consumption at both LT1 (male r =0.66, p <0.001; female LT1 r =0.23, p= 0.177) and LT2 (male r =0.59, p =0.001; female r =0.23, p =0.183) and also with V̇O 2Max (male r =0.60, p =0.001; female r =0.41, p =0.046). Additionally, sub-maximal oxygen consumption varied positively with V̇O 2Max in both male (LT1 r =0.54, p =0.003; LT2 r =0.77, p <0.001) and female athletes (LT1 r =0.88, p <0.001; LT2 r =0.92, p <0.001). Conclusions The results suggest that, while individuals with low mass and good RE can glide economically as they run, larger individuals can compensate for the negative effects their mass has on RE by increasing their capacity to consume oxygen. The elevated energy expenditure of this low-economy high-energy turnover approach to ER may bring costs associated with energy diversion away from other physiological processes, however.
... The elevated TEE in the present study also contrasts with the Constrained Total Energy Expenditure model 57 which suggests that above moderate physical activity levels, TEE plateaus to maintain TEE within a narrow range. Considering the interaction between physical activity and thermoregulation 13,14 , it should be considered the higher physical activity may have simply reduced thermoregulatory energy costs 57 . It is thus recommended to consider cold-induced thermogenesis in future research that aims to develop and refine models on energy expenditure and obesity. ...
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Research investigating thermoregulatory energy costs in free-living humans is limited. We determined the total energy expenditure (TEE) of Tuvan pastoralists living in an extreme cold environment and explored the contribution of physical activity and cold-induced thermogenesis. Twelve semi-nomadic pastoralists (47 ± 8 years, 64 ± 8 kg) living under traditional circumstances, in Tuva, south-central Siberia, Russia, were observed during two consecutive 6-day periods in winter. TEE was measured via the doubly labelled water technique. Skin and ambient temperatures, and physical activity were continuously monitored. The outdoor temperature during the observation period was − 27.4 ± 5.4 °C. During the daytime, the participants were exposed to ambient temperatures below 0 °C for 297 ± 131 min/day. The Tuvan pastoralists were more physically active compared to western populations (609 ± 90 min/day of light, moderate, and vigorous physical activity). In addition, TEE was 13.49 ± 1.33 MJ/day (3224 ± 318 kcal/day), which was significantly larger by 17% and 31% than predicted by body mass, and fat-free mass, respectively. Our research suggests the daily cold exposure combined with high levels of physical activity contributed to the elevated TEE. Future research should reconsider the assumption that energy costs due to thermoregulation are negligible in free-living humans.
... However, there is high certainty evidence about the inverse relationship between PA and all-cause mortality, cardiovascular disease mortality, incident type 2 diabetes [9], and incident site-specific cancers in adults. Still, studies on total energy expenditure showed that these models are not a simple linear function of PA, rather increased PA is associated with reduced energy spent [10]. In other words, total energy expenditure is maintained within a narrow range in a constrained model, and not in an additive one. ...
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The motto "Exercise is a medicine" has reached plethoric tone and the beneficial effects of exercise are nowadays blatant. In the clinical arena, the recommendations of regular physical activity (PA) and exercise are well documented and represent an essential component of primary and secondary prevention strategies [1,2]. However, when it comes to prescription and adherence to exercise training and programs, these behavioural interventions have showed limited efficacy [3]. As a result, physical inactivity remains largely prevalent among general and unhealthy populations. In addition, for people with several chronic diseases, physical inactivity is an increasingly worsening factor. The concept of optimal dose of exercise is still a matter of debate. This is the key for designing individually tailored programs so to yield health benefits, at the minimally conceived level. In a pandemic context of environmental syndromic factors, dose-response studies are urgently advocated to determine the clear-cut therapeutic effects and the multiple health-promoting benefits of exercise.
... It is also important to highlight that although triathletes, a weight-sensitive sport, increased EI, their EA was the lowest among sports, reinforcing our previous findings about the metabolic adaption in the REE observed in triathletes (Silva et al., 2017a). It should also be emphasized that nonexercise activity thermogenesis (i.e., the energy expenditure of unstructured physical activity [Ostendorf et al., 2019]) may have decreased in triathletes, as nonexercise activity thermogenesis has been observed to decrease in the presence of exercise routines (King et al., 2007) and EI restrictions (Martin et al., 2011;Redman et al., 2009), possibly contributing to energy conservation, supporting a constrained TEE model as proposed by Pontzer et al. (2016). Nevertheless, evidence is too scarce to draw any definitive conclusions about the regulation of the energy balance components. ...
Article
During the athletic season, changes in body composition occur due to fluctuations in energy expenditure and energy intake. Literature regarding changes of energy availability (EA) is still scarce. The aim was to estimate EA of athletes from nonweight and weight-sensitive sports during the athletic season (i.e., preparatory and competitive phase). Eighty-eight athletes (19.1 ± 4.2 years, 21.8 ± 2.0 kg/m2, 27% females, self-reported eumenorrheic) from five sports (basketball [n = 29]; handball [n = 7]; volleyball [n = 9]; swimming [n = 18]; and triathlon [n = 25]) were included in this observational study. Energy intake and exercise energy expenditure were measured through doubly labeled water (over 7 days and considering neutral energy balance) and metabolic equivalents of tasks, respectively. Fat-free mass (FFM) was assessed through a four-compartment model. EA was calculated as EA = (energy intake − exercise energy expenditure)/FFM. Linear mixed models, adjusted for sex, were performed to assess EA for the impact of time by sport interaction. Among all sports, EA increased over the season: basketball, estimated mean (SE): 7.2 (1.5) kcal/kg FFM, p < .001; handball, 14.8 (2.9) kcal/kg FFM, p < .001; volleyball, 7.9 (2.8) kcal/kg FFM, p = .006; swimming, 8.7 (2.0) kcal/kg FFM, p < .001; and triathlon, 9.6 (2.0) kcal/kg FFM, p < .001. Eleven athletes (12.5%) had clinical low EA at the preparatory phase and none during the competitive phase. During both assessments, triathletes’ EA was below optimal, being lower than basketballers (p < .001), volleyballers (p < .05), and swimmers (p < .001). Although EA increased in all sports, triathlon’s EA was below optimal during both assessments. Risk of low EA might be seasonal and resolved throughout the season, with higher risk during the preparatory phase. However, in weight-sensitive sports, namely triathlon, low EA is still present.
... Particularly during adulthood, there is a need to increase physical activity levels, as well as to carry out greater planning and control of the energy intake, to avoid deficits that can result in serious pathologies. In adults, the variation in total energy expenditure is only 7% in terms of physical activity levels (Pontzer et al., 2016). ...
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Several studies have investigated the changes that occur in energy expenditure throughout life. In fact, from childhood to old age, human beings go through a series of changes in their life habits, which cause physical and physiological changes in the body, which can influence the energy expenditure of individuals. This brief review aimed to synthesize the determining factors for the change in energy expenditure throughout life, particularly during physical activity. It was concluded that the senescence process and genetic determinants are fundamental for the variability of energy expenditure throughout life.
... 20,21 Recent δ 18 O measurements of body fluids have been conducted almost exclusively with urine, and occasionally with either plasma or serum. 22 ...
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The cover image is based on the Research Article A simple CO2 equilibration method for measuring blood oxygen isotope compositionsy by Daniel R. Green et al., https://doi.org/10.1002/rcm.9256.
... It is thus conceivable that the high volume of exercise training undertaken by endurance-trained athletes reduces BAT volume and 18 F-FDG uptake as an adaptation to high activity energy expenditure levels, while the more moderate exercise training regimens implemented in the present study do not. This hypothesis concurs with the constrained total energy expenditure model, which suggests that low levels of physical activity do not inhibit energyconsuming physiological processes such as BAT thermogenesis 55 , whereas higher levels of physical activity do in order to maintain total daily energy expenditure within a homeostatic range 56,57 . ...
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Exercise modulates both brown adipose tissue (BAT) metabolism and white adipose tissue (WAT) browning in murine models. Whether this is true in humans, however, has remained unknown. An unblinded randomized controlled trial (ClinicalTrials.gov ID: NCT02365129) was therefore conducted to study the effects of a 24-week supervised exercise intervention, combining endurance and resistance training, on BAT volume and activity (primary outcome). The study was carried out in the Sport and Health University Research Institute and the Virgen de las Nieves University Hospital of the University of Granada (Spain). One hundred and forty-five young sedentary adults were assigned to either (i) a control group (no exercise, n=54), (ii) a moderate intensity exercise group (MOD-EX, n=48), or (iii) a vigorous intensity exercise group (VIG-EX n=43) by unrestricted randomization. No important adverse events were recorded. 97 participants (34 men, 63 women) were included in the final analysis (CON; n=35, MOD-EX; n=31, and VIG-EX; n=31). We observed no changes in BAT volume (Δ Control: -22.2±52.6 ml; Δ MOD-EX: -15.5±62.1 ml, Δ VIG-EX: -6.8±66.4 ml; P=0.771) or 18F-fluorodeoxyglucose uptake (SUV peak Δ Control: -2.6±3.1 ml; Δ MOD-EX: -1.2±4.8, Δ VIG-EX: -2.2±5.1; P=0.476) in either the control or the exercise groups. Thus, we did not find any evidence of an exercise-induced change on BAT volume or activity in young sedentary adults.
... However, in recent years, physiological (Pontzer, 2018) and behavioral (Rosenkilde et al., 2012;Silva et al., 2018) compensations have been detected in response to exerciseinduced changes, which has led to conflicting results on weight control by exercise. Of these, some studies observed that an adaptive decrease in non-essential expenditure may occur when exercise interventions result in a negative energy balance, which is called physiological compensation (Pontzer et al., 2016). Additionally, many other studies have found several behavioral compensations, including a decline in non-exercise physical activity (NEPA) (Colley et al., 2010;Schutz et al., 2014;Drenowatz et al., 2015) and increased energy intake (EI) (Stubbs et al., 2002b;Whybrow et al., 2008;Myers et al., 2019), which may minimize or completely offset the exercise-induced increase in energy expenditure. ...
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Objectives: To examine compensatory changes of different exercise durations on non-exercise physical activity (NEPA), appetite, and energy intake (EI) in normal and overweight adults, and to determine if different body mass index of individuals interact with these compensatory effects. Methods: Ten normal weight adults (nine females and one male; age: 24.0 ± 0.4 years; BMI: 20.7 ± 0.5 kg/m ² ) and ten overweight adults (six females and four males; age: 24.5 ± 0.9 years; BMI: 25.9 ± 0.4 kg/m ² ) participated in this study. The participants completed two exercise trials: short-duration continuous training (SDCT) and long-duration continuous training (LDCT), i.e., a 40 min short-duration and an 80 min long-duration continuous training in a randomized order. Total physical activity and NEPA were monitored using an accelerometer for seven consecutive days, which involved a two-day baseline observation period (C-pre-Ex), three-day exercise intervention period (Ex), and two-day follow-up period (C-post-Ex). Blood samples were collected for appetite-related hormone analysis. Appetite score was assessed using the visual analogue scale. Energy intake was evaluated by weighing the food and recording diaries. Results: The NEPA evaluation showed that it was higher for SDCT than for LDCT in the C-post-Ex period (F (1, 19) = 8.508, p = 0.009) in the total sample. Moreover, results also indicated that NEPA was lower for LDCT (F (2, 18) = 6.316, p = 0.020) and higher for SDCT (F (2, 18) = 3.889, p = 0.026) in the C-post-Ex period than in the C-pre-Ex and Ex periods in overweight group. Acyl-ghrelin revealed a main effect of time in the total sample and in normal weight and overweight groups; it was lower in the C-post-Ex period than in the C-pre-Ex and Ex periods (all p < 0.05). Total EI analysis revealed no significant changes in either the total sample or in the normal weight and overweight groups. Conclusion: These findings demonstrate that short duration exercise led to a compensatory increment in NEPA, whereas long duration exercise induced a compensatory decrease in NEPA. Moreover, there was a higher and delayed compensatory response in overweight adults than in normal weight adults. Nevertheless, energy intake was not changed across time, regardless of exercise duration.
... (>230 activity counts per minute per day) activity levels (constrained total energy expenditure model rather than additive model) [175], perhaps due to compensatory mechanisms such as increases in muscle efficiency and decreases in resting energy expenditure [173]. A combination of a low-calorie diet (1200-2000 kcal/day, <30% fat) and moderate-intensity exercise (5 days/week, 225 min/week) resulted in a larger weight loss (10.8%) compared to the diet only, (8.5%) or the exercise-only groups (2.4%) [176]. ...
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Introduction: : The prevalence of both obesity and osteoarthritis (OA) are increasing worldwide (twindemic), and the association between the two chronic diseases is also well-established. Areas covered: : In this narrative review, we will briefly describe the double burdens of both diseases, the impact of weight loss or gain on OA incidence and structural progression and discuss the biomechanical and anti-inflammatory mechanisms mediating these effects. FDA-approved anti-obesity drugs are summarized in terms of their clinical efficacy and safety profile, and the completed or ongoing phase 2/3 clinical trials of such drugs in OA patients with obesity are examined. Expert opinion: : We will discuss the perspectives related to principles of prescription of anti-obesity drugs, the potential role of phenotype-guided approach, time to drug effects in clinical trials, sustainability of weight loss based on the real-world studies, the importance of concomitant therapies such as dieting and exercises, and the role of weight loss on non-weight bearing OA joints. Although obesity is the major risk factor for OA pathogenesis and progression, and there are a variety of anti-obesity medications on the market, research on the use of these disease-modifying drugs in OA (DMOAD) is still sparse..
... Given the high metabolic costs of brain tissue, adaptations to diet and gut morphology may help to meet those costs and release evolutionary constraints on brain size and cognitive capacities (Aiello & Wheeler, 1995;Pontzer et al., 2016;Wrangham, 2009). Foraging challenges may also directly select for cognitive adaptations, because certain feeding strategies (e.g., finding sparse and ephemeral resources like fruits) may demand particular cognitive abilities (e.g., spatial cognition and memory) (Clutton-Brock & Harvey, 1980;Milton, 1998;Rosati, 2018). ...
Chapter
Researchers have studied non-human primate cognition along different paths, including social cognition, planning and causal knowledge, spatial cognition and memory, and gestural communication, as well as comparative studies with humans. This volume describes how primate cognition is studied in labs, zoos, sanctuaries, and in the field, bringing together researchers examining similar issues in all of these settings and showing how each benefits from the others. Readers will discover how lab-based concepts play out in the real world of free primates. This book tackles pressing issues such as replicability, research ethics, and open science. With contributors from a broad range of comparative, cognitive, neuroscience, developmental, ecological, and ethological perspectives, the volume provides a state-of-the-art review pointing to new avenues for integrative research.
... In this paper, we examine the association between daily physical activity and both thyroid hormone levels and immune system biomarkers in a large sample of adult men and women. One framework for understanding the impact of physical activity on other physiological systems is the Constrained Energy Expenditure hypothesis proposed by Pontzer, which posits that increased physical activity leads to reductions in the activity of other (i.e., non-musculoskeletal) systems [15][16][17][18]. This suppression could be evident in global (i.e., whole-body) mediators of metabolic activity, such as thyroid hormone. ...
Article
The acute effects of exercise on metabolic energy expenditure and inflammation are well studied, but the long-term effects of regular daily physical activity on metabolic and endocrine effects are less clear. Further, prior studies investigating the impact of daily physical activity in large cohorts have generally relied on self-reported activity. Here, we used the U.S. National Health and Nutrition Examination Survey (NHANES) to investigate the relationship between daily physical activity and both thyroid and immune activity. Daily physical activity was assessed through accelerometry or accelerometry-validated survey responses. Thyroid activity was assessed from circulating levels of thyroid stimulating hormone (TSH) and thyroxine (T4). Immune function was assessed from circulating cytokines (C-reactive protein [CRP], immunoglobulin E [IgE], fibrinogen) and blood cell counts. In general linear models including body mass index, age, gender, activity and TSH as factors, active adults had a lower levels of T4 and reduced slope of the TSH:T4 relationship. Similarly, greater physical activity was associated with lower CRP and fibrinogen levels (but not IgE) and lower white blood cell, basophil, monocyte, neutrophil, and eosinophil (but not lymphocyte) counts. Daily physical activity was also associated with lower prevalence of clinically elevated CRP, WBC, and lymphocytes in a dose-response manner. These results underscore the long-term impact of daily physical activity on both systemic metabolic activity (thyroid) and on specific physiological tasks (immune). The regulatory effects of physical activity on other bodily systems are clinically relevant and should be incorporated into public health strategies promoting exercise.
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Key points: A higher net (above resting) energy cost of walking (lower gait economy) is observed in adults with obesity compared to lean individuals. Understanding the mechanisms (i.e., mass driven, gait pattern and behavioural changes) involved in this extra cost of walking in adults with obesity is pivotal to optimizing the use of walking to promote daily physical activity and improve health in these individuals. We found that very large weight loss induced by bariatric surgery significantly decreased the energy cost of walking per kg of body mass after 1 year with similar total mechanical work per kg of body mass, resulting in an increased mechanical efficiency of walking. Individuals with obesity may reorganize their walking pattern into a gait more similar to normal body mass adults, thus decreasing their energy cost of walking by making their muscles work more efficiently. Abstract: Understanding the mechanisms involved in the higher energy cost of walking (NCw : the energy expenditure above resting per unit distance) in adults with obesity is pivotal to optimizing the use of walking in weight management programmes. Therefore, this study aimed to investigate the mechanics, energetics and mechanical efficiency of walking after a large body mass loss induced by bariatric surgery in individuals with obesity. Nine adults (39.5 ± 8.6 yr; BMI: 42.7 ± 4.6 kg·m-2 ) walked at five fixed speeds before (baseline) and after the bariatric surgery (post 1 and post 2). Gas exchanges were measured to obtain NCw . A motion analysis system and instrumented treadmill were combined to assess total mechanical work (Wtot ). Mechanical efficiency (Wtot ·NCw -1 ) was also calculated. Participants lost 25.7 ± 3.4% of their body mass at post 1 (6.6 months; P<0.001) and 6.1 ± 4.9% more at post 2 (12 months; P = 0.014). Mass-normalized NCw was similar between baseline and post 1 and decreased at post 2 compared to that at baseline (-6.2 ± 2.7%) and post 1 (-8.1 ± 1.9%; P≤0.007). No difference was found in mass-normalized Wtot during follow-up (P = 0.36). Mechanical efficiency was similar at post 1 and post 2 when compared to that at baseline (P≥0.19), but it was higher (+14.1 ± 4.6%) at post 2 than at post 1 (P = 0.013). These findings showed that after a very large body mass loss, individuals with obesity may reorganize their walking pattern into a gait more similar to that of lean adults, thus decreasing their NCw by making their muscles work more efficiently. This article is protected by copyright. All rights reserved.
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Objectives: Bone is a dynamic organ under continual turnover influenced by life history stage, energy dynamics, diet, climate, and disease. Bone turnover data have enormous potential in biological anthropology for testing evolutionary and biocultural hypotheses, yet few studies have integrated these biomarkers. In the present article we systematically review the current availability, future viability, and applicability of measuring bone turnover markers (BTMs) in dried blood spot (DBS) samples obtained from finger prick whole blood. Methods: Our review considers clinical and public health relevance, biomarker stability in DBS, assay availability, and cost. We consider biomarkers of bone formation such as osteocalcin (bone matrix protein), PINP (N-terminal propeptide of type I collagen), and alkaline phosphatase (osteoblast enzyme), as well as biomarkers of bone resorption such as CTX (marker of collagen breakdown) and TRACP5b (tartrate-resistant acid phosphatase 5b; osteoclast enzyme). Results: Two BTMs have been validated for DBS: osteocalcin (formation) and TRACP5b (resorption). Prime candidates for future development are CTX and PINP, the formation and resorption markers used for clinical monitoring of response to osteoporosis treatment. Conclusion: BTMs are a field-friendly technique for longitudinal monitoring of skeletal biology during growth, reproduction and aging, combining minimized risk to study participants with maximized ease of sample storage and transport. This combination allows new insights into the effects of energy availability, disease, and physical activity level on bone, and questions about bone gain and loss across life history and in response to environmental factors; these issues are important in human biology, paleoanthropology, bioarchaeology, and forensic anthropology.
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Understanding the impacts of activity on energy balance is crucial. Increasing levels of activity may bring diminishing returns in energy expenditure because of compensatory responses in non-activity energy expenditures.1, 2, 3 This suggestion has profound implications for both the evolution of metabolism and human health. It implies that a long-term increase in activity does not directly translate into an increase in total energy expenditure (TEE) because other components of TEE may decrease in response—energy compensation. We used the largest dataset compiled on adult TEE and basal energy expenditure (BEE) (n = 1,754) of people living normal lives to find that energy compensation by a typical human averages 28% due to reduced BEE; this suggests that only 72% of the extra calories we burn from additional activity translates into extra calories burned that day. Moreover, the degree of energy compensation varied considerably between people of different body compositions. This association between compensation and adiposity could be due to among-individual differences in compensation: people who compensate more may be more likely to accumulate body fat. Alternatively, the process might occur within individuals: as we get fatter, our body might compensate more strongly for the calories burned during activity, making losing fat progressively more difficult. Determining the causality of the relationship between energy compensation and adiposity will be key to improving public health strategies regarding obesity.
Article
Energy balance is the fine regulation of energy expenditure and energy intake. Negative energy balance causes body weight loss, while positive energy balance promotes weight gain. Modern societies offer a maladapted way of life, where easy access to palatable foods and the lack of opportunities to perform physical activity are considered the roots of the obesity pandemic. Physical exercise increases energy expenditure and, consequently, is supposed to promote weight loss. Paradoxically, physical exercise acutely drives anorexigenic-like effects, but the mechanisms are still poorly understood. Using an evolutionary background, this review aims to highlight the potential involvement of the melanocortin system and other hypothalamic neural circuitries regulating energy balance during and after physical exercise. The physiological significance of these changes will be explored, and possible signalling agents will be addressed. The knowledge discussed here might be important for clarifying obesity aetiology as well as new therapeutic approaches for body weight loss.
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A lifetime of change Measurements of total and basal energy in a large cohort of subjects at ages spanning from before birth to old age document distinct changes that occur during a human lifetime. Pontzer et al . report that energy expenditure (adjusted for weight) in neonates was like that of adults but increased substantially in the first year of life (see the Perspective by Rhoads and Anderson). It then gradually declined until young individuals reached adult characteristics, which were maintained from age 20 to 60 years. Older individuals showed reduced energy expenditure. Tissue metabolism thus appears not to be constant but rather to undergo transitions at critical junctures. —LBR
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The role of physical activity (PA) in the regulation of body weight is still a major topic of debate. This may be because studies have essentially focused on the effects of moderate/vigorous PA (MVPA) on body weight while overlooking the other components of PA, namely, light-intensity PA (LPA, daily life activities) and sedentary behaviors (SB, too much sitting). In this review, we will (i) describe the history of changes in PA behaviors that occurred with modernization; (ii) review data from cross-sectional and longitudinal studies that examined the associations between PA, SB, and measures of obesity; (iii) review interventional studies that investigated the effects of changes in PA and SB on body weight and adiposity; and (iv) discuss experimental studies that addressed potential biological mechanisms underlying the effects of PA and SB on weight regulation. Overall recent findings support the importance of considering all components of PA to better understand the regulation of energy balance and suggest an important role for LPA and SB in addition to MVPA on body weight regulation. Longitudinal large-scale rigorous studies are needed to advance our knowledge of the role of PA/SB in combating the obesity epidemic.
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Even in complete rest, the organism requires a minimum amount of energy to maintain minimal physical activity and body temperature, as well as various cell functions. This basal metabolic rate accounts for about two-thirds of the total energy consumption under everyday stress. More than 80% of this is distributed alone on.
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Reducing sedentary behaviour (SB) and increasing physical activity (PA) by sitting less and standing/walking more is advised to prevent chronic diseases. However, the mechanisms underlying this recommendation are not well-established, especially in individuals with obesity living in low-income regions. The present study evaluated whether there are associations between PA indicators (PAI – standing time, walking time, and the number of steps/day) and SB indicators (SBI - sitting/lying down time) with the hormonal profile and resting energy expenditure (REE) of adult women living in a low-income region. This is a cross-sectional study. We collected data on hormones (insulin resistance, leptin, and thyroid axis), body composition (tetrapolar bioimpedance), REE (indirect calorimetry), and PAI and SBI (triaxial accelerometers, ActivPAL). Multivariable linear models adjusting for age and fat-free mass were performed. Fifty-eight women (mean age of 31 years and body mass index of 33 kg/m ² ) were included. The mean sitting/lying down time and standing time were 16.08 and 5.52 h/day, respectively. Sitting/lying down time showed a direct association with free thyroxine (FT 4 ) (β = 0.56 ng/dL; 95%CI = −1.10; −0.02). Standing time showed a direct association with FT 4 (β = 0.75 ng/dL; 95% CI = 0.01; 1.48) and inverse association with free triiodothyronine (β = −2.83 pg/mL 95%CI = −5.56; −0.10). There were no associations between PAI and SBI with the REE, insulin resistance, leptin and thyroid-stimulating hormone. Thus, decreased SB is associated with thyroid hormones levels but not with REE, insulin resistance or leptin in women with obesity living in low-income regions.
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Background & Aims Resting Energy Expenditure (REE) quantitatively describes the calories used to support body function (e.g. breathing, blood circulation, etc.) at resting condition. Assessment of the REE is essential for successful weight management and the understanding of metabolic health. REE is typically determined via indirect calorimetry. Current biomedical indirect calorimetry technologies, utilizing assessment of oxygen consumption (VO2) and carbon dioxide production (VCO2) rates (which are typically in the form factor of a metabolic cart) are bulky and require on-site calibration and/or trained professionals to operate. We introduce a novel wearable medical device with FDA clearance to determine REE accurately, portable, and user-friendly format, which can be used both by health professionals in a clinical environment and by the patient at home. Previously, we have reported the validation of Breezing Med (also named as Breezing ProTM) through Douglas Bag Method, a gold standard for gas exchange measurement, and excellent agreement has been found between the two methods for the determination of REE, VO2, and VCO2 rates.¹ Now we present the validation of Breezing Med against Medical Graphics (MGC) CPX UltimaTM, a FDA 510k cleared metabolic cart, which principle is based on breath-by-breath analysis. In addition, we present Breezing Med as a tool for daily measurement of metabolic rate by the lay person at home. Methods A) The validation study was executed via parallel measurement of 20 healthy participants under resting conditions using both the Breezing Med and the MGC Ultima CPXTM (10 min test). B) Breezing Med measurements were carried out by six subjects at home during stay-at-home order due to COVID-19 for 30 days. Results A) The resulting measurements from both devices was compared with correlation slope’s and R-squared coefficients close to 1. B) Results were recorded and analyzed for variability. The pilot study demonstrated the advantage of Breezing Med device to be easy-to-use at home by lay people, which make the valuable device for telemedicine applications related to weight management from home. Conclusions This result shows that the MGC Ultima CPXTM and Breezing Med are substantially equivalent for REE measurement; and an advantage of this device for metabolic assessment under the current COVID-19 pandemic situation, for people with impaired physical mobility, and for those who lives in rural areas or face impediments that limit physical access to care.
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Here, we demonstrate that a naturally evolving behavior (allonursing) has greater effect on reproductive power (mass per unit of time) and output (litter mass at birth) than does artificial selection (domestication). Additionally, we demonstrate the importance of resource optimization afforded by sociality (rather than resource abundance per se) in shaping a species’ life history profile and its ability to overcome its own physiological constraints. Maternal resource availability and metabolism have a strong limiting effect on reproductive output. Allomaternal care and domestication increase the energy available to the mother and should correlate with an increase in reproductive output. Here, we take a comparative approach to understand how this increase is accomplished (e.g., litter mass, reproductive frequency, etc.) and the strength of the effect among different forms of external energetic supplementation. We find that domestication and all forms of allocare correlate with increased fertility. All forms of provisioning correlate with larger litters without compromising offspring size. The greatest increase we observe in reproductive power is in species that practice allonursing. Our results suggest that the ultimate factor limiting reproductive output in placental mammals is maternal metabolic power rather than resource availability.
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“The Biggest Loser” weight-loss competition offered a unique opportunity to investigate human energy metabolism and body composition before, during, and after an extreme lifestyle intervention. Here, I reinterpret the results of “The Biggest Loser” study in the context of a constrained model of human energy expenditure. Specifically, “The Biggest Loser” contestants engaged in large, sustained increases in physical activity that may have caused compensatory metabolic adaptations to substantially decrease resting metabolic rate and thereby minimize changes in total energy expenditure. This interpretation helps explain why the magnitude of persistent metabolic adaptation was largest in contestants with the greatest increases in sustained physical activity and why weight-loss interventions involving lower levels of physical activity have not measured similarly large metabolic adaptations. Additional longitudinal studies quantifying the interrelationships between various components of energy expenditure and energy intake are needed to better understand the dynamics of human body weight regulation.
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Metabolism and cancer intersect in multiple ways. Cancer has unique metabolic properties, including an inordinate reliance on anaerobic glycolysis (the Warburg effect). From an evolutionary standpoint, increased cancer incidence is associated with increased metabolic rates across species. Epidemiological data prove that a group of overlapping metabolic alterations, including obesity, type II Diabetes Mellitus, non-alcoholic fatty liver disease, and metabolic syndrome, constitute predisposing risk factors for cancer development in multiple anatomical sites. The molecular pathways underpinning this association involve hyperinsulinemia, hyperglycemia, sex hormones, adipokines, chronic inflammation, oxidative stress, and altered immune response.
Chapter
Exercise/physical activity (PA) can reduce susceptibility to many chronic conditions including obesity and associated metabolic disorders (type 2 diabetes, nonalcoholic fatty liver disease), cardiovascular disease, and certain cancers with benefits on cognition, mood, and general well‐being. The premise that exercise/PA is associated with significant weight loss dates is linked with an observation in 1958 that adipose tissue is energy‐dense containing 3500 calories/pound. To achieve energy balance, EI must equal EE. Strategies to combat excess weight gain, aside from the obvious reduction of EI, would also include increased EE through PA. The chapter examines the relationship between weight loss and improvements in weight‐related comorbidities. Multiple short bouts of walking have been assessed as a tool for weight loss modality on the assumption that multiple SB of walking may achieve more weight loss or be easier to finish than one LB of walking.
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Background: Approximately 30% of the global population is affected by obesity. Traditional non-surgical measures for weight loss have limited efficacy and tolerability. Therefore, there is a need for novel, effective therapies. Brown adipose tissue (BAT) has been implicated in physiological energy expenditure, indicating that it could be targeted to achieve weight loss in humans. The use of [18 F]-fluorodeoxyglucose (18 F-FDG) positron emission tomography - computed tomography (PET-CT) imaging has enabled the discovery of functionally active BAT in the supraclavicular, subclavian, and thoracic spine regions of human adults. This review aims to discuss the reasons behind the renewed interest in BAT, assess whether it is metabolically important in humans, and evaluate its feasibility as a therapeutic target for treating obesity. Sources of material: PubMed Central, Europe PMC, Medline FINDINGS: In vivo studies have shown that BAT activity is regulated by thyroid hormones and the sympathetic nervous system. Furthermore, BAT uniquely contains uncoupling protein 1 (UCP1) that is largely responsible for non-shivering thermogenesis. Cold exposure can increase BAT recruitment through the browning of white adipose tissue (WAT); however, this technique has practical limitations that may preclude its use. Currently available medicines for humans, such as the β3-adrenergic receptor agonist mirabegron or the farnesoid X receptor agonist obeticholic acid, have generated excitement, although adverse effects are a concern. Capsinoids represent a tolerable alternative which require further investigation. Conclusions: The use of currently available BAT-activating agents alone is unlikely to achieve significant weight loss in humans. A combination of BAT activation with physical exercise and modern, successful dietary strategies represents a more realistic option. This article is protected by copyright. All rights reserved.
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Low total energy expenditure (TEE, MJ/d) has been a hypothesized risk factor for weight gain, but repeatability of TEE, a critical variable in longitudinal studies of energy balance, is understudied. We examine repeated doubly labeled water (DLW) measurements of TEE in 348 adults and 47 children from the IAEA DLW Database (mean ± SD time interval: 1.9 ± 2.9 y) to assess repeatability of TEE, and to examine if TEE adjusted for age, sex, fat-free mass, and fat mass is associated with changes in weight or body composition. Here, we report that repeatability of TEE is high for adults, but not children. Bivariate Bayesian mixed models show no among or within-individual correlation between body composition (fat mass or percentage) and unadjusted TEE in adults. For adults aged 20–60 y ( N = 267; time interval: 7.4 ± 12.2 weeks), increases in adjusted TEE are associated with weight gain but not with changes in body composition; results are similar for subjects with intervals >4 weeks ( N = 53; 29.1 ± 12.8 weeks). This suggests low TEE is not a risk factor for, and high TEE is not protective against, weight or body fat gain over the time intervals tested.
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The relationships between metabolic rate, body temperature (Tb), body composition and ageing are complex, and not fully resolved. In particular, Tb and metabolic rate often change in parallel, making disentangling their effects difficult. Here we show that in both sexes of mice and hamsters exposure to a temperature of 32.5 °C leads to a reduced lifespan, coincident with lowered metabolic rate and elevated Tb with no change in body composition. We exploit the unique situation that when small mammals are exposed to hot ambient temperatures their Tb goes up, at the same time that their metabolic rate goes down, allowing us to experimentally separate the impacts of Tb and metabolic rate on lifespan. The impact of ambient temperature on lifespan can be reversed by exposing the animals to elevated heat loss by forced convection, which reverses the effect on Tb but does not affect metabolic rate, demonstrating the causal effect of Tb on lifespan under laboratory conditions for these models. The impact of manipulations such as calorie restriction that increase lifespan may be mediated via effects on Tb, and measuring Tb may be a useful screening tool for putative therapeutics to extend the human lifespan.
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Background Up to 30% of community-based older adults report reduced appetite and energy intake (EI), but previous research examining the underlying physiological mechanisms have focused on the mechanisms that suppress eating rather than the hunger drive and EI. Objective To examine the associations between fat-free mass (FFM), physical activity (PA), total daily energy expenditure (TDEE) and self-reported EI in older adults. Methods The present study was a secondary analysis of The Interactive Diet and Activity Tracking in AARP Study. Body composition (deuterium dilution), PA (accelerometry) and TDEE (doubly labelled water) were measured in 590 older adults (age = 63.1 ± 5.9 years; BMI = 28.1 ± 4.9 kg/m2). Total daily EI was estimated from a single 24-hour dietary recall (EIsingle; ± one month of PA and TDEE measurement) and the mean of up to six recalls over a 12-month period (EImean), with mis-reporters classified using the 95% confidence intervals between EImean and TDEE. Results After controlling for age and sex, linear regression demonstrated that FFM and TDEE predicted EI when estimated from a single 24-hour dietary recall (p < 0.05), the mean of up to six dietary recalls (p < 0.05) and after the removal of those classified as under-reporters (p < 0.001). Age moderated the associations between FFM and EIsingle (p < 0.001), FFM and EImean (p < 0.001), and TDEE with EIsingle (p = 0.016), with associations becoming weaker across age quintiles. Conclusions These data suggest that total daily EI is proportional to FFM and TDEE, but not fat mass, in older adults. These associations may reflect an underling drive to eat that influences daily food intake. While the associations between FFM or TDEE and EI existed across all age quintiles, these associations weakened with increasing age. Trial Registration The Interactive Diet and Activity Tracking in AARP (IDATA) Study was registered at clinicaltrials.gov as: NCT03268577 (http://www.clinicaltrials.gov).
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Physical fitness, achieved through regular exercise and/or spontaneous physical activity, confers resilience by inducing positive psychological and physiological benefits, blunting stress reactivity, protecting against potentially adverse behavioural and metabolic consequences of stressful events and preventing many chronic diseases. In this review, we discuss the biological mechanisms underlying the beneficial effects of physical fitness on mental and physical health. Physical fitness appears to buffer against stress-related disease owing to its blunting/optimizing effects on hormonal stress responsive systems, such as the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. This blunting appears to contribute to reduced emotional, physiological and metabolic reactivity as well as increased positive mood and well-being. Another mechanism whereby regular exercise and/or physical fitness may confer resilience is through minimizing excessive inflammation. Chronic psychological stress, physical inactivity and abdominal adiposity have been associated with persistent, systemic, low-grade inflammation and exert adverse effects on mental and physical health. The anti-inflammatory effects of regular exercise/activity can promote behavioural and metabolic resilience, and protect against various chronic diseases associated with systemic inflammation. Moreover, exercise may benefit the brain by enhancing growth factor expression and neural plasticity, thereby contributing to improved mood and cognition. In summary, the mechanisms whereby physical fitness promotes increased resilience and well-being and positive psychological and physical health are diverse and complex.
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In many interventions that are based on an exercise program intended to induce weight loss, the mean weight loss observed is modest and sometimes far less than the individual expected. The individual responses are also widely variable, with some individuals losing a substantial amount of weight, others maintaining weight, and a few actually gaining weight. The media have focused on the sub-population that loses little weight, contributing to a public perception that exercise has limited utility to cause weight loss. The purpose of the symposium was to present recent, novel data that help explain how compensatory behaviors contribute to a wide discrepancy in exercise-induced weight loss. The presentations provide evidence that some individuals adopt compensatory behaviors, i.e. increased energy intake and/or reduced activity, that offset the exercise energy expenditure and limit weight loss. The challenge for both scientists and clinicians is to develop effective tools to identify which individuals are susceptible to such behaviors, and to develop strategies to minimize their impact.
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Western lifestyles differ markedly from those of our hunter-gatherer ancestors, and these differences in diet and activity level are often implicated in the global obesity pandemic. However, few physiological data for hunter-gatherer populations are available to test these models of obesity. In this study, we used the doubly-labeled water method to measure total daily energy expenditure (kCal/day) in Hadza hunter-gatherers to test whether foragers expend more energy each day than their Western counterparts. As expected, physical activity level, PAL, was greater among Hadza foragers than among Westerners. Nonetheless, average daily energy expenditure of traditional Hadza foragers was no different than that of Westerners after controlling for body size. The metabolic cost of walking (kcal kg(-1) m(-1)) and resting (kcal kg(-1) s(-1)) were also similar among Hadza and Western groups. The similarity in metabolic rates across a broad range of cultures challenges current models of obesity suggesting that Western lifestyles lead to decreased energy expenditure. We hypothesize that human daily energy expenditure may be an evolved physiological trait largely independent of cultural differences.
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The prevalence of obesity has increased in societies of all socio-cultural backgrounds. To date, guidelines set forward to prevent obesity have universally emphasized optimal levels of physical activity. However there are few empirical data to support the assertion that low levels of energy expenditure in activity is a causal factor in the current obesity epidemic are very limited. The Modeling the Epidemiologic Transition Study (METS) is a cohort study designed to assess the association between physical activity levels and relative weight, weight gain and diabetes and cardiovascular disease risk in five population-based samples at different stages of economic development. Twenty-five hundred young adults, ages 25-45, were enrolled in the study; 500 from sites in Ghana, South Africa, Seychelles, Jamaica and the United States. At baseline, physical activity levels were assessed using accelerometry and a questionnaire in all participants and by doubly labeled water in a subsample of 75 per site. We assessed dietary intake using two separate 24-hour recalls, body composition using bioelectrical impedance analysis, and health history, social and economic indicators by questionnaire. Blood pressure was measured and blood samples collected for measurement of lipids, glucose, insulin and adipokines. Full examination including physical activity using accelerometry, anthropometric data and fasting glucose will take place at 12 and 24 months. The distribution of the main variables and the associations between physical activity, independent of energy intake, glucose metabolism and anthropometric measures will be assessed using cross-section and longitudinal analysis within and between sites. METS will provide insight on the relative contribution of physical activity and diet to excess weight, age-related weight gain and incident glucose impairment in five populations' samples of young adults at different stages of economic development. These data should be useful for the development of empirically-based public health policy aimed at the prevention of obesity and associated chronic diseases.
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There is an assumption that people in developing countries have a higher total energy expenditure (TEE) and physical activity level (PAL) than do people in developed nations, but few objective data for this assertion exist. We conducted a meta-analysis of TEE and PAL by using data from countries that have a low or middle human development index (HDI) compared with those with a high HDI to better understand how energy-expenditure variables are associated with development status and population differences in body size. We performed a literature search for studies in which energy expenditure was measured by using doubly labeled water. Mean data on age, weight, body mass index (BMI; in kg/m(2)), TEE, and PAL were extracted, and HDI status was assessed. Pooled estimates of the mean effect by sex were obtained, and the extent to which age, weight, HDI status, and year of publication explained heterogeneity was assessed. A total of 98 studies (14 studies from low- or middle-HDI countries) that represented 183 cohorts and 4972 individuals were included. Mean (±SE) BMI was lower in countries with a low or middle HDI than in those with a high HDI for both men and women (22.7 ± 1.0 compared with 26.0 ± 0.7, respectively, in men and 24.3 ± 0.7 compared with 26.6 ± 0.4, respectively, in women). In meta-regression models, there was an inverse association of age (P < 0.001) and a positive association of weight (P < 0.001) with TEE for both sexes; there was an association of age only in men with PAL (P < 0.001). There was no association of HDI status with either TEE or PAL. TEE adjusted for weight and age or PAL did not differ significantly between developing and industrialized countries, which calls into question the role of energy expenditure in the cause of obesity at the population level.
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Foraging adaptations include behavioral and physiological responses, but most optimal foraging models deal exclusively with behavioral decision variables, taking other dimensions as constraints. To overcome this limitation, we measured behavioral and physiological responses of European starlings Sturnus vulgaris to changes in food availability in a laboratory environment. The birds lived in a closed economy with a choice of two foraging modes (flying and walking) and were observed under two treatments (hard and easy) that differed in the work required to obtain food. Comparing the hard with the easy treatment, we found the following differences. In the hard treatment, daily amount of work was higher, but daily intake was lower. Even though work was greater, total daily expenditure was smaller, partly because overnight metabolism was lower. Body mass was lower, but daily oscillation in body mass did not differ. Feces' caloric density was lower, indicating greater food utilization. Energy expenditure rate expressed as multiples of basal metabolic rate (BMR) increased during the working period from 3.5 x BMR (easy) to 5.2 x BMR (hard), but over the 24-h period, it was close to 2.4 x BMR in both treatments. We also found that rate of expenditure during flight was very high in both treatments (52.3 W in easy and 45.5 W in hard), as expected for short (as opposed to cruising) flights. The relative preferences between walking and flying were incompatible with maximizing the ratio of energy gains per unit of expenditure (efficiency) but compatible with maximizing net gain per unit of time during the foraging cycle (net rate). Neither currency explained the results when nonforaging time was included. Time was not a direct constraint: the birds rested more than 90% of the time in both treatments. Understanding this complex picture requires reasoning with ecological, physiological, and cognitive arguments. We defend the role of optimality as an appropriate tool to guide this integrative perspective.
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Daily human energy requirements calculated from separate components of energy expenditure are inaccurate and usually in poor agreement with measured energy intakes. Measurement of energy expenditure over periods of 24 h or longer is needed to determine more accurately rates of daily energy expenditure in humans. We provide a detailed description of a human respiratory chamber and methods used to determine rates of energy expenditure over 24-h periods in 177 subjects. The results show that: fat-free mass (FFM) as estimated by densitometry is the best available determinant of 24-h energy expenditures (24EE) and explains 81% of the variance observed between individuals (24EE [kcal/d] = 597 + 26.5 FFM); 24EE in an individual is very reproducible (coefficient of variation = 2.4%); and even when adjusted for differences in FFM, there is still considerable interperson variability of the daily energy expenditure. A large portion of the variability of 24EE among individuals, independent of differences in body size, was due to variability in the degree of spontaneous physical activity, i.e., "fidgeting," which accounted for 100-800 kcal/d in these subjects.
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This review was undertaken to determine whether exercise-induced weight loss was associated with corresponding reductions in total, abdominal, and visceral fat in a dose-response manner. A literature search (MEDLINE, 1966--2000) was performed using appropriate keywords to identify studies that consider the influence of exercise-induced weight loss on total and/or abdominal fat. The reference lists of those studies identified were cross-referenced for additional studies. Total fat. Review of available evidence suggested that studies evaluating the utility of physical activity as a means of obesity reduction could be subdivided into two categories based on study duration. Short-term studies (< or = 16 wk, N = 20) were characterized by exercise programs that increased energy expenditure by values double (2200 vs 1100 kcal.wk-1) that of long-term studies (> or = 26 wk, N = 11). Accordingly, short-term studies report reductions in body weight (-0.18 vs -0.06 kg x wk(-1)) and total fat (-0.21 vs -0.06 kg x wk(-1)) that are threefold higher than those reported in long-term studies. Moreover, with respect to dose-response issues, the evidence from short-term studies suggest that exercise-induced weight loss is positively related to reductions in total fat in a dose-response manner. No such relationship was observed when the results from long-term studies were examined. Abdominal fat. Limited evidence suggests that exercise-induced weight loss is associated with reductions in abdominal obesity as measured by waist circumference or imaging methods; however, at present there is insufficient evidence to determine a dose-response relationship between physical activity, and abdominal or visceral fat. In response to well-controlled, short-term trials, increasing physical activity expressed as energy expended per week is positively related to reductions in total adiposity in a dose-response manner. Although physical activity is associated with reduction in abdominal and visceral fat, there is insufficient evidence to determine a dose-response relationship.
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Oxidative metabolism has reactive oxygen species (ROS) as unavoidable by-products, and the damage ROS inflicts on DNA, proteins and lipids is considered to be a major agent of senescence. Increasing reproductive effort accelerates senescence, but whether reproductive effort is increased at the expense of protection against oxidative damage has not yet been tested. We manipulated reproductive effort in zebra finches through brood size manipulation and measured the activity of two major antioxidant enzymes (superoxide dismutase (SOD) and glutathione peroxidase (GPx)) in the pectoral muscle after 19-20 days of brood rearing. Oxidative stress is reflected by the balance between oxidative protection and ROS exposure, and we therefore scaled SOD and GPx activity to daily energy expenditure (DEE) as an index of ROS production. SOD and GPx activity decreased with increasing brood size by 28% and 24%, respectively. This effect was identical in the two sexes, but arose in different ways: males did not change their DEE, but had lower absolute enzyme activity, and females increased their DEE, but did not change absolute enzyme activity. This result suggests that senescence acceleration by increased reproductive effort is at least in part mediated by oxidative stress.
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Obesity occurs when energy intake exceeds energy expenditure. Humans expend energy through purposeful exercise and through changes in posture and movement that are associated with the routines of daily life [called nonexercise activity thermogenesis (NEAT)]. To examine NEAT's role in obesity, we recruited 10 lean and 10 mildly obese sedentary volunteers and measured their body postures and movements every half-second for 10 days. Obese individuals were seated, on average, 2 hours longer per day than lean individuals. Posture allocation did not change when the obese individuals lost weight or when lean individuals gained weight, suggesting that it is biologically determined. If obese individuals adopted the NEAT-enhanced behaviors of their lean counterparts, they might expend an additional 350 calories (kcal) per day.
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Understanding the effect of food availability on food requirements is critical when linking food availability e.g. to reproduction or habitat selection. Decreasing intake rate (intake per unit foraging effort) can be expected to increase daily energy expenditure (DEE), due to increased foraging costs. However, all the studies we could find that have tested this hypothesis (with one exception) found DEE to be constant or decreasing when intake rate was experimentally decreased. This may be due to the design of the reward schedule, which can be fixed (e.g. 20 units effort required for each reward) or variable (e.g. each unit effort rewarded with probability 1/20). Most studies used fixed reward rates, but foraging motivation is generally higher for variable reward rates, and the only study in which animals increased DEE when intake rate decreased used variable reward rates. To assess the generality of this result, we exposed zebra finches Taeniopygia guttata to different intake rates using variable reward rates. We decreased intake rate by mixing 25 g of seeds with 0, 25 or 75 g of chaff. With increasing chaff/seed ratio the time spent foraging increased from 6% to 27%, but this was insufficient to compensate for the lower intake rate, because DEE decreased by 6.6%. Body mass was independent of chaff/seed ratio. Effects of intake rate on foraging time and DEE were stronger at lower temperatures, when DEE was higher. The decrease in DEE in adverse conditions raises the question of what prevents such behaviour in benign circumstances. We hypothesize that energy is saved at the expense of ;condition', and we tested this hypothesis in two ways. Firstly, we tested the effect of intake rate on the replacement of two plucked tail feathers (a form of somatic repair). Replacement feathers were shorter when intake rate was low, indicating an effect of intake rate on somatic repair ability. Secondly, we tested for carry-over effects of intake rate on reproduction, by giving pairs the opportunity to reproduce with access ad libitum to food after feeding on one of the three chaff/seed ratios for 6 weeks. The interval until laying the first egg increased with decreasing intake rate in the preceding 6 weeks. The effects of intake rate on somatic maintenance and reproduction may explain why birds sustained higher metabolic rates than apparently necessary, but the physiological mechanisms determining the optimal metabolic rate remain to be discovered.
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A Correction has been published for this article in Statistics in Medicine 2001; 20:655.
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The identification of changes in the recent trend is an important issue in the analysis of cancer mortality and incidence data. We apply a joinpoint regression model to describe such continuous changes and use the grid-search method to fit the regression function with unknown joinpoints assuming constant variance and uncorrelated errors. We find the number of significant joinpoints by performing several permutation tests, each of which has a correct significance level asymptotically. Each p-value is found using Monte Carlo methods, and the overall asymptotic significance level is maintained through a Bonferroni correction. These tests are extended to the situation with non-constant variance to handle rates with Poisson variation and possibly autocorrelated errors. The performance of these tests are studied via simulations and the tests are applied to U.S. prostate cancer incidence and mortality rates.
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This review examines the proximate, ecological, and evolutionary determinants of energy expenditure in humans and primates, with an emphasis on empirical measurements of total energy expenditure (TEE). Body size is the main proximate determinant of TEE, both within and between species; physical activity, genetic variation, and endocrine regulation explain substantially less of the variation in TEE. Basal metabolism is the single largest component of TEE, far exceeding the cost of physical activity, digestion, growth and reproduction, and thermoregulation in most instances. Notably, differences in physical activity do not generally result in corresponding differences in TEE, undermining the utility of activity-based factorial estimates of TEE. Instead, empirical measurements of energy expenditure in humans and other primates suggest that the body adapts dynamically to long-term changes in physical activity, maintaining TEE within an evolved, and relatively narrow, physiological range.
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The human body adapts dynamically to maintain total energy expenditure, TEE, within a narrow physiological range. Rather than increasing with physical activity in a dose-dependent manner, experimental and ecological evidence indicates that TEE is a relatively constrained product of our evolved physiology. The body adapts to changes in physical activity to keep total energy expenditure in check.
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A grid-search method of fitting segmented regression curves with unknown transition points is described and compared with a standard method. It is shown to be suitable for fitting a wider class of models than the standard method and to provide as a by-product a way of making reliable inferences about the abscissae of the transitions.
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Significance Measurements of daily energy expenditure indicate that primates, including humans, expend only half of the calories expected for mammals of similar body size. As energy expenditure is central to organismal biology, these results hold important implications for life history, evolutionary biology, and foraging ecology for primates and other mammals. Specifically, we show that primates’ remarkably low metabolic rates account for their distinctively slow rates of growth, reproduction, and aging.
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Procedures are outlined for obtaining maximum likelihood estimates and likelihood confidence regions in the intersecting two-phase linear regression model. The procedures are illustrated on a small set of data, and the distributional properties are examined empirically.
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The field of application of accelerometry is diverse and ever expanding. Because by definition all physical activities lead to energy expenditure, the doubly labelled water (DLW) method as gold standard to assess total energy expenditure over longer periods of time is the method of choice to validate accelerometers in their ability to assess daily physical activities. The aim of this paper was to provide a systematic overview of all recent (2007-2011) accelerometer validation studies using DLW as the reference. The PubMed Central database was searched using the following keywords: doubly or double labelled or labeled water in combination with accelerometer, accelerometry, motion sensor, or activity monitor. Limits were set to include articles from 2007 to 2011, as earlier publications were covered in a previous review. In total, 38 articles were identified, of which 25 were selected to contain sufficient new data. Eighteen different accelerometers were validated. There was a large variability in accelerometer output and their validity to assess daily physical activity. Activity type recognition has great potential to improve the assessment of physical activity-related health outcomes. So far, there is little evidence that adding other physiological measures such as heart rate significantly improves the estimation of energy expenditure.
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Weight loss resulting from an exercise intervention tends to be lower than predicted. Modest weight loss can arise from an increase in energy intake, physiological reductions in resting energy expenditure, an increase in lean tissue or a decrease in non-exercise activity. Lower than expected, weight loss could also arise from weak and invalidated assumptions within predictive models. To investigate these causes, we systematically reviewed studies that monitored compliance to exercise prescriptions and measured exercise-induced change in body composition. Changed body energy stores were calculated to determine the deficit between total daily energy intake and energy expenditures. This information combined with available measurements was used to critically evaluate explanations for low exercise-induced weight loss. We conclude that the small magnitude of weight loss observed from the majority of evaluated exercise interventions is primarily due to low doses of prescribed exercise energy expenditures compounded by a concomitant increase in caloric intake.
Article
To study zebra finch allocation of energy to day and night at two different workloads, we assessed the daily energy turnover from: (1) metabolizable energy of the food, and (2) doubly-labeled water. In both experiments we imposed two levels of activity on captive zebra finches (Taeniopygia guttata), by applying different computer-controlled workload schedules. A low workload required 20 hops, and a high workload 40 hops to obtain 10 s access to food. In experiment 1, we further measured nocturnal energy expenditure by overnight oxygen consumption. From experiment 2 we derived an estimate of the costs of hopping activity, from inter-individual association of daily amount of hopping and daily energy expenditure. Surprisingly, the daily energy budget was, on average, reduced slightly when birds were subjected to a high workload. Since hopping activity was 50% higher during the high workload than during the low workload, the birds apparently compensated, even over-compensated, for the increased energetic demands of activity. Nocturnal energy expenditure was indeed reduced for the high workload, which was largely due to a reduction in resting metabolic rate. Economizing on energy was more than could have been accomplished by a reduction in mass alone, and we discuss the occurrence and potential mechanisms of physiological compensation. The amount of energy saved during the night did account for part of the total amount of energy saved. We surmise that the strategy of energetic compensation observed during the night was extended into the inactive hours of the day.
Article
During the past decade, skeletal muscle has been identified as a secretory organ. Accordingly, we have suggested that cytokines and other peptides that are produced, expressed and released by muscle fibres and exert either autocrine, paracrine or endocrine effects should be classified as myokines. The finding that the muscle secretome consists of several hundred secreted peptides provides a conceptual basis and a whole new paradigm for understanding how muscles communicate with other organs, such as adipose tissue, liver, pancreas, bones and brain. However, some myokines exert their effects within the muscle itself. Thus, myostatin, LIF, IL-6 and IL-7 are involved in muscle hypertrophy and myogenesis, whereas BDNF and IL-6 are involved in AMPK-mediated fat oxidation. IL-6 also appears to have systemic effects on the liver, adipose tissue and the immune system, and mediates crosstalk between intestinal L cells and pancreatic islets. Other myokines include the osteogenic factors IGF-1 and FGF-2; FSTL-1, which improves the endothelial function of the vascular system; and the PGC-1α-dependent myokine irisin, which drives brown-fat-like development. Studies in the past few years suggest the existence of yet unidentified factors, secreted from muscle cells, which may influence cancer cell growth and pancreas function. Many proteins produced by skeletal muscle are dependent upon contraction; therefore, physical inactivity probably leads to an altered myokine response, which could provide a potential mechanism for the association between sedentary behaviour and many chronic diseases.
Article
Female deer mice, Peromyscus maniculatus, and house mice, Mus domesticus=musculus, were challenged to reproduce while working for their food. Animals were subjected to one of several increasingly greater work requirements by using a caging system in which a food-pellet dispenser was controlled by wheel-running activity. Locomotor behaviour, food consumption and body weights were assessed continuously during pre-reproduction, pregnancy and lactation. Peromyscus and Mus differed in the magnitude and temporal dimensions of their locomotor effort; however, both species often ran far more wheel revolutions than necessary to generate the number of food pellets eaten, except during lactation when females invested all of their wheel-running into obtaining food. Peromyscus maintained greater body weights, supported greater litter masses, and produced more pups at weaning than their Mus counterparts, but Peromyscus also required less food per unit of mass than Mus. Most Peromyscus females maintained at the highest work levels did not attempt reproduction. Among Peromyscus that did become pregnant, litter size at birth and at weaning averaged five or six pups, regardless of feeding conditions. Peromyscus pups became increasingly stunted as females worked harder but obtained less food. Mus females allowed insemination and attempted lactation regardless of feeding conditions, but they routinely cannibalized offspring throughout the first 12 days of lactation. Thus, as litter size was reduced, most surviving Mus pups attained similar body weights at weaning. There was no evidence of sex-ratio adjustments in either species. In conclusion, Peromyscus females exhibited a rigid ‘all-or-nothing’ reproductive response, typically increasing their feeding effort to support large litters, whereas Mus females eliminated pups to stabilize the energy burdens of lactation. The divergent energy-allocation strategies employed by female Peromyscus and Mus appear correlated with their respective tendencies for seasonally oriented versus opportunistic breeding in the wild.
Article
The visual information on a scatterplot can be greatly enhanced, with little additional cost, by computing and plotting smoothed points. Robust locally weighted regression is a method for smoothing a scatterplot, (x i , y i ), i = 1, …, n, in which the fitted value at z k is the value of a polynomial fit to the data using weighted least squares, where the weight for (x i , y i ) is large if x i is close to x k and small if it is not. A robust fitting procedure is used that guards against deviant points distorting the smoothed points. Visual, computational, and statistical issues of robust locally weighted regression are discussed. Several examples, including data on lead intoxication, are used to illustrate the methodology.
Article
Actical accelerometer thresholds have been derived to enable objective measurement of time spent performing sedentary activity in children and adolescents, but not adults. Thus, the purpose of this study was to determine Actical accelerometer sedentary activity thresholds for adults. Data were available from 3187 participants aged 6 to 79 years from a preliminary partial dataset of the Canadian Health Measures Survey, who wore an Actical for 7 days. Step count data were used to evaluate the use of 50, 100, and 800 counts per min (cpm) as sedentary activity thresholds. Minutes when no steps were recorded were considered minutes of sedentary activity. The use of higher cpm thresholds resulted in a greater percentage of sedentary minutes being correctly classified as sedentary. The percentage of minutes that were incorrectly classified as sedentary was substantially higher when using a threshold of 800 cpm compared with 50 or 100 cpm. Results were similar for children, adolescents, and adults. These findings suggest that a threshold of 100 cpm is appropriate for classifying sedentary activity of adults when using the Actical. As such, wear periods with minutes registering less than 100 cpm would be classified as time spent performing sedentary activity.
Article
Accelerometry is increasingly used as a physical activity surveillance device that can quantify the amount of time spent moving at a range of intensities. This study proposes physical activity intensity cut-points for the Actical accelerometer. Thirty-eight volunteers completed a multi-stage treadmill protocol at 3, 5, and 8 km · h⁻¹ (2, 3.3, and 8 METs) while wearing Actical accelerometers initialized to collect data in 60-s epochs. Using a decision boundary analytical approach, moderate and vigorous physical activity intensity cut-points were derived for the Actical accelerometer. In adults (n = 26), the cut-point for moderate physical activity intensity occurred at 1535 counts per minute and the vigorous cut-point occurred at 3960 counts per minute. In children (n = 12), the cut-point for moderate physical activity intensity occurred at 1600 counts per minute and the vigorous cut-point occurred at 4760 counts per minute. Improved classification of physical activity intensity using the decision boundary cut-points was observed compared with using mean values for each protocol stage. The cut-points derived are recommended for use in adults. The cut-points derived for children confirm the findings of previous studies.
Article
This is a review of bootstrap methods, concentrating on basic ideas and applications rather than theoretical considerations. It begins with an exposition of the bootstrap estimate of standard error for one-sample situations. Several examples, some involving quite complicated statistical procedures, are given. The bootstrap is then extended to other measures of statistical accuracy such as bias and prediction error, and to complicated data structures such as time series, censored data, and regression models. Several more examples are presented illustrating these ideas. The last third of the paper deals mainly with bootstrap confidence intervals.
Article
We studied the effect of an increase in physical activity on energy balance and body composition without interfering with energy intake (EI). Sixteen women and sixteen men, aged 28-41 years, body mass index 19.4-26.4 kg/m2, not participating in any sport before the start of the experiment, prepared to run a half-marathon competition after 44 weeks. Measurements of body composition, EI and energy expenditure (EE) were performed before (0 weeks), and 8, 20, and 40 weeks after the start of training. Body composition was measured with hydrodensitometry and isotope dilution, and EI with a 7 d dietary record. EE was measured overnight in a respiration chamber (sleeping metabolic rate (SMR)) and in a number of subjects over 2-week intervals with doubly-labelled water (average daily metabolic rate (ADMR)). ADMR showed an average increase of 30% in both sexes from the start of training onwards while SMR tended to decrease. EI showed a tendency to drop from week 20 to week 40 in the men and a tendency to increase from week 20 to week 40 in the women. Body mass (BM) did not change in both sexes until the observation at 40 weeks when the median value of the change in men was -1.0 kg (P < 0.01; Wilcoxon signed-rank) while the corresponding change of -0.9 kg in the women was not statistically significant. Body composition changes were most pronounced in men as well. Based on changes in BM, body volume and total body water, men lost 3.8 kg fat mass (FM) (P < 0.001; Wilcoxon signed-rank) and gained 1.6 kg protein mass (P < 0.01; Wilcoxon signed-rank) while the corresponding changes in women were 2.0 kg (P < 0.05; Wilcoxon signed-rank) and 1.2 kg (P < 0.05; Wilcoxon signed-rank). In men the loss of FM was positively correlated with the initial percentage body fat (Pearson r 0.92, P < 0.001). In conclusion, body fat can be reduced by physical activity although women tend to compensate for the increased EE with an increased EI, resulting in a smaller effect on BM and FM compared with men.
Article
A novel caging system was used to study the interrelationships between foraging effort, food intake, growth and sexual maturation of peripubertal female mice. Females housed in these cages were forced to work (forage) at various intensities in order to obtain food pellets. It is argued that this is a biologically more meaningful approach to understanding the energetics of sexual development than the traditional approach of simple underfeeding. Female mice exhibited a cascade of developmental adjustments and deficits when challenged to forage harder for less food. The functions most sensitive to increased foraging effort were sexual development and growth in body length; growth in body weight was intermediate and fat deposition was least sensitive of all. The relative insensitivity of fat deposition to higher foraging costs suggests a strategy for survival during the postweaning dispersal movements of the wild ancestors of the laboratory mouse. Finally, regression analyses suggested that heavier females who had less than average body fat and higher than average food intake achieved their pubertal ovulation most rapidly.
Article
The identification of changes in the recent trend is an important issue in the analysis of cancer mortality and incidence data. We apply a joinpoint regression model to describe such continuous changes and use the grid-search method to fit the regression function with unknown joinpoints assuming constant variance and uncorrelated errors. We find the number of significant joinpoints by performing several permutation tests, each of which has a correct significance level asymptotically. Each p-value is found using Monte Carlo methods, and the overall asymptotic significance level is maintained through a Bonferroni correction. These tests are extended to the situation with non-constant variance to handle rates with Poisson variation and possibly autocorrelated errors. The performance of these tests are studied via simulations and the tests are applied to U.S. prostate cancer incidence and mortality rates.
Article
Natural selection favors the optimal allocation of energy and other limiting resources to reproduction. Human reproductive physiology displays characteristic patterns that can be viewed as mechanisms that help optimize reproductive effort in the face of environmental energetic constraints. Female ovarian function is particularly sensitive to energy balance and energy flux, resulting in a synchronization of conception with favorable energetic conditions. Reproductive effort during gestation is highly buffered from environmental energetic constraints, but the duration of gestation and final birthweight are both very sensitive to maternal energy availability. Milk production during lactation is relatively buffered from maternal energetic constraints as well, but the duration of lactational amenorrhea is sensitive to the relative metabolic load of lactation. Male gamete production is very insensitive to energetic constraints, but variation in testosterone production in response to both age and longer-lasting energetic conditions contributes to the modulation of somatic and behavioral aspects of male reproductive effort, aspects that are more energetically costly for a male. There is also new evidence that testosterone may also help to modulate the trade-off between male parenting and mating effort.
Article
Non-exercise activity thermogenesis (NEAT) is the energy expended that is not from sleeping, eating or sports-like exercise. It ranges from the energy expended walking to work, typing, performing yard work, undertaking agricultural tasks and fidgeting. NEAT can be measured by one of two approaches. The first approach is to measure or estimate total NEAT. Here, total daily energy expenditure is measured and from it is subtracted BMR + thermic effect of food. The second is the factoral approach whereby the components of NEAT are quantified and total NEAT calculated by summing these components. The amount of NEAT that human subjects perform represents the product of the amount and types of physical activities and the thermogenic cost of each activity. The factors that affect the NEAT of a human subject are readily divisible into biological factors, such as weight, gender and body composition, and environmental factors, such as occupation or dwelling within a 'concrete jungle'. The combined impact of these factors explains the substantial variance in human NEAT. The variability in NEAT might be viewed as random but human data contradict this perception. It appears that changes in NEAT subtly accompany experimentally-induced changes in energy balance and are important in the physiology of weight change. NEAT and sedentariness may thus be important in obesity. It then becomes intriguing to dissect mechanistic studies that delineate how NEAT is regulated by neural, peripheral and humoral factors. NEAT may be a carefully-regulated 'tank' of physical activity that is crucial for weight control.
Article
To describe physical activity levels of children (6-11 yr), adolescents (12-19 yr), and adults (20+ yr), using objective data obtained with accelerometers from a representative sample of the U.S. population. These results were obtained from the 2003-2004 National Health and Nutritional Examination Survey (NHANES), a cross-sectional study of a complex, multistage probability sample of the civilian, noninstitutionalized U.S. population in the United States. Data are described from 6329 participants who provided at least 1 d of accelerometer data and from 4867 participants who provided four or more days of accelerometer data. Males are more physically active than females. Physical activity declines dramatically across age groups between childhood and adolescence and continues to decline with age. For example, 42% of children ages 6-11 yr obtain the recommended 60 min x d(-1) of physical activity, whereas only 8% of adolescents achieve this goal. Among adults, adherence to the recommendation to obtain 30 min x d(-1) of physical activity is less than 5%. Objective and subjective measures of physical activity give qualitatively similar results regarding gender and age patterns of activity. However, adherence to physical activity recommendations according to accelerometer-measured activity is substantially lower than according to self-report. Great care must be taken when interpreting self-reported physical activity in clinical practice, public health program design and evaluation, and epidemiological research.
Global Recommendations on Physical Activity for Health (World Health Organization)
World Health Organization (2010). Global Recommendations on Physical Activity for Health (World Health Organization).
Obesity and overweight
World Health Organization (2014). Obesity and overweight. Fact Sheet No. 311. http://www.who.int/mediacentre/factsheets/fs311/en/.