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The Role of Energy Expenditure in the Differential Weight Loss in Obese Women on Low-Fat and Low-Carbohydrate Diets
Abstract
We have recently reported that obese women randomized to a low-carbohydrate diet lost more than twice as much weight as those following a low-fat diet over 6 months. The difference in weight loss was not explained by differences in energy intake because women on the two diets reported similar daily energy consumption. We hypothesized that chronic ingestion of a low-carbohydrate diet increases energy expenditure relative to a low-fat diet and that this accounts for the differential weight loss. To study this question, 50 healthy, moderately obese (body mass index, 33.2 +/- 0.28 kg/m(2)) women were randomized to 4 months of an ad libitum low-carbohydrate diet or an energy-restricted, low-fat diet. Resting energy expenditure (REE) was measured by indirect calorimetry at baseline, 2 months, and 4 months. Physical activity was estimated by pedometers. The thermic effect of food (TEF) in response to low-fat and low-carbohydrate breakfasts was assessed over 5 h in a subset of subjects. Forty women completed the trial. The low-carbohydrate group lost more weight (9.79 +/- 0.71 vs. 6.14 +/- 0.91 kg; P < 0.05) and more body fat (6.20 +/- 0.67 vs. 3.23 +/- 0.67 kg; P < 0.05) than the low-fat group. There were no differences in energy intake between the diet groups as reported on 3-d food records at the conclusion of the study (1422 +/- 73 vs. 1530 +/- 102 kcal; 5954 +/- 306 vs. 6406 +/- 427 kJ). Mean REE in the two groups was comparable at baseline, decreased with weight loss, and did not differ at 2 or 4 months. The low-fat meal caused a greater 5-h increase in TEF than did the low-carbohydrate meal (53 +/- 9 vs. 31 +/- 5 kcal; 222 +/- 38 vs. 130 +/- 21 kJ; P = 0.017). Estimates of physical activity were stable in the dieters during the study and did not differ between groups. These results confirm that short-term weight loss is greater in obese women on a low-carbohydrate diet than in those on a low-fat diet even when reported food intake is similar. The differential weight loss is not explained by differences in REE, TEF, or physical activity and likely reflects underreporting of food consumption by the low-fat dieters.
... -588 g ± 140 g (SEM), p = 0.78. Although this observation is consis-tent with various diet trails that show that RC diets lead to analogous or better fat loss than an isocaloric RF diets (Brehm et al., 2003(Brehm et al., , 2005Bazzano et al., 2014;Kong et al., 2020;Buga et al., 2021;Iacovides et al., 2022) the authors underestimated the importance of such discrepancy by arguing that, in a timeframe of just 6 days, DXA measurements lack of the appropriate sensitivity to correctly detect the cumulative fat loss differences identified by equation (6). Measurements of the drop in leptin levels, however, appear to reject such claim: RC diet: -3.89 ng/ mL ± 0.81 ng/mL (SEM) vs RF diet: -2.89 ng/mL ± 0.86 ng/mL (SEM), p = 0.39. ...
... Journal of Theoretical Biology xxx (xxxx) 111240 Data in the first four rows are simulation inputs. Energy expenditure (EE) is assumed to be similar among diets (Hall et al., 2016;Hall and Guo, 2017;Hall et al., 2019;Brehm et al., 2005) and to remain constant for 6 days. Numbers in the remaining rows were calculated by the following equations: Assuming nitrogen (N) balance, daily urinary nitrogen equals (Protein intake)/6.25; ...
... Avg. excretion = [(DXA fat loss) -(Equation (6) An immediate consequence of equation (7) is that insulin now emerges as a modulator of fat loss since the excretion of fatty acid derivatives is inversely related to levels of this hormone (e.g., ketone bodies). Consequently, a diet that elevates insulin secretion elicits fat loss mainly through net fat oxidation whereas a diet that decreases insulin secretion evokes fat loss largely by increasing the excretion of fatty acids derivatives with minimal impact on net fat oxidation since daily energy expenditure appears to be unaltered (Hall et al., 2015(Hall et al., , 2016Hall and Guo, 2017;Hall et al., 2019;Brehm et al., 2005). As a result, a more coherent interpretation of Hall et al. (2015) study is as follows: ...
Metabolic physiology asserts that body weight stability is achieved when over time the average absorbed energy intake equals the average expended energy. This principle, known as energy balance, justifies the design of numerous investigations that aim to elucidate the biology of obesity. The present work provides a mathematical analysis that demonstrates, nonetheless, that weight stability must coexist with a constant energy imbalance, i.e., the average absorbed energy intake and the average expended energy are significantly different during steady weight periods. This analytical finding is not in contradiction with the First Law of Thermodynamics since open systems can manifest a stable mass in the absence of energy equilibrium. The effect of caloric imbalance on weight fluctuations is thus the result of its underlying net mass flux. The energy balance theory is, consequently, an inconsistent paradigm; and as such, the data analysis and interpretation that follows from its postulates is expected to be erroneous.
... In numerous publications LCDs lead to greater weight loss in comparison to isocaloric LFDs [10,11,12,13,14,15]. Whether the diminished mass intake, present in LCDs relative to isocaloric LFDs, explains or contributes to this apparent advantage remains unknown. ...
... These axioms also lead to a simple mathematical model that is used to contrast LCDs against isocaloric LFDs. According to the EBT the most probable explanation for the superior weight loss evoked by LCDs vs. LFDs is EI underreporting by low-fat dieters as typically no substantial differences are found between the EEs of both groups [14]. A recent in-patient study defies this hypothesis as the LCD advantage persists even when the energy intake is precisely measured and no energy imbalance differences are found [15]. ...
... Àw LFD k Þ ¼ 5:95kg in the LFD. These differences, which are in close agreement with experimental data [10,11,12,13,14,15], emerge from the interaction between the variables governing the weight loss kinetics, namely, Mand R.To appreciate this, let us apply Eq. (3) to each diet ...
Energy metabolism theory affirms that body weight stability is achieved as over time the average energy intake equals the average energy expenditure, a state known as energy balance. Here it is demonstrated, however, that weight stability coexists with a persistent energy imbalance. Such unexpected result emerges as a consequence of the answers to three fundamental problems: 1. Is it possible to model body weight fluctuations without the energy balance theory? And if so, what are the benefits over the energy balance strategy? 2. During energy balance, how the oxidized macronutrient distribution that underlies the average energy expenditure is related to the macronutrient distribution of the average energy intake? 3. Is energy balance possible under a low-fat diet that simultaneously satisfies the following conditions? (a) The fat fraction of the absorbed energy intake is always less than the oxidized fat fraction of the energy expenditure. (b) The carbohydrate fraction of the absorbed energy intake is always greater or equal to the oxidized carbohydrate fraction of the energy expenditure. The first of these issues is addressed with the axiomatic method while the rest are managed through analythical arguments. On the whole, this analysis identifies inconsistencies in the principle of energy balance. The axiomatic approach results also in a simple mass balance model that fits experimental data and explains body composition alterations. This model gives rise to a convincing argument that appears to elucidate the advantage of low-carbohydrate diets over isocaloric low-fat diets. It is concluded, according to the aforementioned model, that weight fluctuations are ultimately dependent on the difference between daily food mass intake and daily mass loss (e.g., excretion of macronutrient oxidation products) and not on energy imbalance. In effect, it is shown that assuming otherwise may caused unintended weight gain.
... Diet-only interventions comprised a total of 400 participants with a median sample size of 18 (range 5-66). NRT included a median sample size of 23 (range 6-66), RT of 17 (range 5-57) and RCT of 15 (range [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. ...
... EI was also prescribed as a reduction of 2929 kJ/d (34) , 3347 kJ/d (43) and 1682 kJ/d (33) . EI was not reported in one study (27) . ...
... Sex. Seven studies included women only (14,27,29,33,37,49,51) , one study included men only (34) and six studies included a combined sample of women and men (15,16,22,28,35,43) . ...
Non-exercise physical activity (NEPA) and/or non-exercise activity thermogenesis (NEAT) reductions may occur from diet and/or exercise-induced negative energy balance interventions, resulting in less-than-expected weight loss. This systematic review describes the effects of prescribed diet and/or physical activity (PA)/exercise on NEPA and/or NEAT in adults. Studies were identified from PubMed, web-of-knowledge, Embase, SPORTDiscus, ERIC and PsycINFO searches up to 1 March 2017. Eligibility criteria included randomised controlled trials (RCT), randomised trials (RT) and non-randomised trials (NRT); objective measures of PA and energy expenditure; data on NEPA, NEAT and spontaneous PA; ≥10 healthy male/female aged>18 years; and ≥7 d length. The trial is registered at PROSPERO-2017-CRD42017052635. In all, thirty-six articles (RCT-10, RT-9, NRT-17) with a total of seventy intervention arms (diet, exercise, combined diet/exercise), with a total of 1561 participants, were included. Compensation was observed in twenty-six out of seventy intervention arms (fifteen studies out of thirty-six reporting declines in NEAT (eight), NEPA (four) or both (three)) representing 63, 27 and 23 % of diet-only, combined diet/exercise, and exercise-only intervention arms, respectively. Weight loss observed in participants who decreased NEAT was double the weight loss found in those who did not compensate, suggesting that the energy imbalance degree may lead to energy conservation. Although these findings do not support the hypothesis that prescribed diet and/or exercise results in decreased NEAT and NEPA in healthy adults, the underpowered trial design and the lack of state-of-the-art methods may limit these conclusions. Future studies should explore the impact of weight-loss magnitude, energetic restriction degree, exercise dose and participant characteristics on NEAT and/or NEPA.
... Table 1 summarizes the objectives, methods, subjects, and major results of the studies included in this review article. The vast majority of the research reported a decrease in fat-free mass after following a ketogenic diet (Brehm et al., 2005;Brehm et al. 2003;Brinkworth et al. 2009 (a);Brinkworth et al., 2009 (b);Johnstone et al. 2008;Landers et al. 2002;Noakes et al., 2006;Ruth et al., 2013;Wood et al., 2007;Yancy et al. 2004), while two studies reported no change (Johnston et al., 2006;Paoli et al., 2012), and one study reported an increase (Volek et al., 2002). The quantity of fat-free mass lost was ~1 -3.5 kg, while the majority of the studies reported weight loss of ~5 -13 kg and fat mass loss of ~3.5 -11 kg. ...
... Almost all other located studies reported greater weight loss than Volek et al., and a number of studies intentionally imposed a caloric deficit. Energy restriction of ~25 -30% was implemented in several studies (Brinkworth 2009 (a); Brinkworth et al. 2009 (b);Johnston et al., 2006;Ruth et al., 2013), but others did not specifically assign a level of energy intake (Brehm et al., 2005(Brehm et al., , 2003Johnstone et al., 2008;Landers et al., 2002;Wood et al., 2007;Yancy et al., 2004). ...
... Several studies utilized ad libitum diets in regards to fat and protein (Brehm et al., 2005(Brehm et al., , 2003Landers et al., 2002;Yancy et al., 2004), while others prescribed specific intake guidelines for all macronutrients (Johnston et al., 2006;Johnstone et al., 2008;Noakes et al., 2006;Volek et al., 2002;Wood et al., 2007). The studies assigning macronutrient intake implemented diets with ~30 -35% of energy intake from protein, ~60 -65% from fat, and ~5 -10% from carbohydrate. ...
Low-carbohydrate and very-low-carbohydrate diets are often employed as weight loss strategies in exercising individuals and athletes. Very-low-carbohydrate diets can lead to a state of ketosis, in which the concentration of blood ketones (acetoacetate, 3-β-hydroxybutyrate, and acetone) increases due to increased fatty acid breakdown and activity of ketogenic enzymes. A potential concern of these "ketogenic" diets, as with other weight loss diets, is the potential loss of fat-free mass (e.g. skeletal muscle). Upon examination of the literature, the majority of studies report decreases in fat-free mass in individuals following a ketogenic diet. However, some confounding factors exist, such as the use of aggressive weight loss diets and potential concerns with fat-free mass measurement. A limited number of studies have examined combining resistance training with ketogenic diets, and further research is needed to determine whether resistance training can effectively slow or stop the loss of fat-free mass typically seen in individuals following a ketogenic diet. Mechanisms underlying the effects of a ketogenic diet on fat-free mass and the results of implementing exercise interventions in combination with this diet should also be examined.
... The primary and secondary reviewers independently extracted data from all qualified publications for the systematic review (n = 34) (13,17,24,25,27,38,41,(44)(45)(46)(47)(48) and meta-analysis (n = 10) (24,25,27,38,(52)(53)(54)(55)(56)(57). The following data were extracted from each publication: author, publication year, title, study design, study duration, sample population description, intervention group, group sample size, group mean age, menopausal status, BMI, prescribed energy restriction, exercise intervention, quantity and source of protein intake, quantity of vitamin D intake, quantity of calcium intake, method of diet administration, assessment of dietary compliance, and the pre-and post-intervention or net absolute changes in measurements of bone quantity (BMD or BMC, or a combination). ...
... Risk-of-bias assessment is described in Table 1. Eleven articles displayed a low risk of selection and performance bias due to clear reporting of the randomization method, allocation concealment, and blinding techniques (44,45,53,55,59,61,64,67,69,71,73). However, the vast majority failed to fully report on such details and thus showed an unclear risk of selection or performance bias (n = 20) (13, 17, 24, 25, 27, 38, 41, 46-48, 52, 54, 56, 57, 60, 63, 66, 68, 70, 72). ...
Research supports the hypothesis that higher total protein intake during weight loss promotes retention of lean soft tissue, but the effect of dietary protein quantity on bone mass, a lean hard tissue, is inconsistent. The purpose of this systematic review and meta-analysis was to assess the effect of dietary protein quantity [higher protein (HP): ≥25% of energy from protein or ≥1.0 g · kg body wt-1 · d-1; normal protein (NP): <25% of energy from protein or <1.0 g · kg body wt-1 · d-1] on changes in bone mineral density (BMD) and content (BMC; total body, lumbar spine, total hip, femoral neck) following a prescribed energy restriction. We hypothesized that an HP diet would attenuate the loss of BMD/BMC following weight loss in comparison to an NP diet. Two researchers systematically and independently screened 2366 publications from PubMed, Cochrane, Scopus, CINAHL, and Web of Science Core Collection and extracted data from 34 qualified publications. Inclusion criteria included the following: 1) healthy subjects ≥19 y; 2) a prescribed energy restriction; 3) measurements of total protein intake, BMD, and BMC; and 4) an intervention duration of ≥3 mo. Data from 10 of the 34 publications with 2 groups of different total protein intakes were extracted and used to conduct a random-effects model meta-analysis. A majority of publications (59%) showed a decrease in bone quantity following active weight loss, regardless of total protein intake. Statistically, the loss of total BMD (P = 0.016; weighted mean difference: +0.006 g/cm2; 95% CI: 0, 0.011 g/cm2) and lumbar spine BMD (P = 0.019; weighted mean difference: +0.017 g/cm2; 95% CI: 0.001, 0.033 g/cm2) was attenuated with an HP versus an NP weight-loss diet. However, the clinical significance is questionable given the modest weighted mean difference and study duration. Higher total protein intake does not exacerbate but may attenuate the loss of bone quantity following weight loss.
... In line with this physiological pathway, individuals with acceptable insulin function who follow low-carbohydrate diets theoretically should experience ketonemia without acidemia, illness or any metabolic complication [23,24]. Indeed, some previous studies have determined that the production of ketone bodies during a VLCK-diet suggests that the diet-induced ketonemia is a well-tolerated process [25][26][27], even in type 2 diabetic patients [28]. However, the acidity constant of ketones and its implication in the pathophysiology of ketoacidosis in diabetic and alcoholic patients [29][30][31] have generated debate in terms of the acid-base safety of this type of diets. ...
... Several studies have shown the high value of the VLCK diets as a weight-loss treatment [8][9][10][11][25][26][27], but its theoretical acid-base safety had not yet to be studied in depth. ...
Background and aims:
Very low-calorie ketogenic (VLCK) diets have been consistently shown to be an effective obesity treatment, but the current evidence for its acid-base safety is limited. The aim of the current work was to evaluate the acid-base status of obese patients during the course of a VLCK diet.
Method:
Twenty obese participants undertook a VLCK diet for 4 months. Anthropometric and biochemical parameters, and venous blood gases were obtained on four subsequent visits: visit C-1 (baseline); visit C-2, (1-2 months); maximum ketosis; visit C-3 (2-3 months), ketosis declining; and visit C-4 at 4 months, no ketosis. Results were compared with 51 patients that had an episode of diabetic ketoacidosis as well as with a group that underwent a similar VLCK diet in real life conditions of treatment.
Results:
Visit C1 blood pH (7.37 ± 0.03); plasma bicarbonate (24.7 ± 2.5 mmol/l); plasma glucose (96.0 ± 11.7 mg/l) as well as anion gap or osmolarity were not statistically modified at four months after a total weight reduction of 20.7 kg in average and were within the normal range throughout the study. Even at the point of maximum ketosis all variables measured were always far from the cut-off points established to diabetic ketoacidosis.
Conclusion:
During the course of a VLCK diet there were no clinically or statistically significant changes in glucose, blood pH, anion gap and plasma bicarbonate. Hence the VLCK diet can be considered as a safe nutritional intervention for the treatment of obesity in terms of acid-base equilibrium.
... Ostatecznie mechanizm ten, prowadząc do spirali insulina-głód, jest nie tylko źródłem nieuzasadnionego podjadania, ale przede wszystkim otyłości i związanych z nią problemów zdrowotnych. W opinii wielu ekspertów [46][47][48][49] ograniczanie konsumpcji węglowodanów, zwłaszcza tych o wysokim indeksie glikemicznym (IG), skutkuje pozytywną zmianą proporcji pomiędzy wydzielaną w nadmiarze insuliną a glukagonem. Sprzyja to lepszemu wykorzystaniu zgromadzonej w wątrobie glukozy na potrzeby energetyczne ustroju, glikogenu mięśniowego, ale również wolnych kwasów tłuszczowych. ...
... Działanie to poprzez rozkład tłuszczów sprzyja redukcji tkanki tłuszczowej, a przy tym wolne kwasy tłuszczowe (w przeciwieństwie do insuliny) nie pobudzają podwzgórza do prowokowania nieuzasadnionego biologicznie podjadania. Wyniki badań wspomnianych naukowców [46][47][48][49] dowodzą, że korzystniejsze rezultaty długoterminowe (w odniesieniu do masy ciała oraz wskaźników biochemicznych krwi) uzyskuje się przy zastosowaniu diet niskowęglowodanowych niż diet niskotłuszczowych. ...
Introduction: Despite studies to determine reasons for and to contain the global obesity epidemics, the 20+ year old population is gaining weight. The education by health training participation is a chance for a parallel work towards the nutrition habit change, the need to learn new or master old movement skills, and the discipline and motivation maintenance.
Purpose: Indication of the necessity of systemic obesity therapy solutions by ensuring the patient’s health training participation, self-regulated physical activity education, balanced diet introduction and psychological support.
Method: Systemic design method analysis to determine the optimal health training design algorithm.
Results: Health training design activity algorithm as per the modified analysis methods and Nadler’s systemic synthesis in the context of selected systemic concepts.
Conclusions: The systemic obesity therapy by health training participation and goal-setting education is a process whose effects will last long and result in the population’s physical condition improvement, irrespective of individual effects. activity algorithm as per the modified analysis methods and Nadler’s systemic synthesis in the context of selected systemic concepts.
... Samaha et al. (2003) suggested that low-carbohydrate intake has an obvious effect on fat loss [47]. Similar results have been reported by Brehm [48]. ...
This study aimed to examine the effects of supervised fitness training under the guidance of a personal trainer and those of competitive fitness training with others and reveal the effects of specific differences between them in a detailed manner. The study's participants consisted of 66 healthy male adults (age: 29.2 ± 5.4 years). The participants were divided into three groups: the individual training group (n = 21), which served as the control group; the exercising with a partner group (n = 22); and the group trained by a personal trainer (n = 23). Each participant was subsequently assessed using one repetition maximum bench press, squats, skeletal muscle mass, fat mass, and a questionnaire regarding nutritional plan and injury to compare the effects of training sessions over a period of 12 weeks. Among the three groups, only the group trained by a personal trainer showed an obvious enhancement in fat reduction compared to baseline (-1.61 kg, p = 0.033), which was suggestive of a salient trend that far surpassed those of the individual training group and the exercising with a partner group. Regarding squats, only the group trained by a personal trainer showed a significant change compared to the individual training group (p = 0.003). Regarding the participants' consistent use of a nutritional plan, only the group trained by a personal trainer exhibited a palpable tendency (p < 0.001); furthermore, the effect of preventing injury in the group trained by a personal trainer was more notable than that in the individual training group and the exercising with a partner group. Our results indicate that a fitness personal trainer service is effective in expediting the process of achieving fitness goals in a relatively safe manner, thereby substantiating the diversified values of the fitness personal trainer service.
... However, it appears that the protein intake in our KD condition (26.0 ± 2.9% of total energy intake) was similar to what other studies have reported when participants were allowed to consume protein ad libitum (53)(54)(55). Thus, allowing ad libitum intake of protein during the KD condition appears to be a practical way to reduce the burden on participants to find low-protein high-fat foods. ...
... Some studies have studied both the acute-and long-term effect on metabolism and weight management of different diets. As part of a larger weight loss study in obese women eight participants took part in a sub-study on the effect on PPEE from varying macronutrient composition (232). After ingestion of two different meals with caloric content of 540 kcal, consisting of either low-carbohydrate (5 E% carbohydrate, 26 E% protein and 69 E% fat) or high-carbohydrate meal (69 E% carbohydrate, 11 E% protein and 20 E% fat). ...
... On the other hand, it is possible that some greatly restricted carbohydrates to allow adequate protein intake. Deriving energy from proteins is an expensive process for the body, which may lead to calorie consumption and greater WL as compared with diets that rely on carbohydrates as the main energy source [31][32][33]. In fact, during carbohydrate restriction most of the body's glucose requirements are satisfied by gluconeogenesis from amino acids, a process that requires approximately 400-600 kcal/d [32]. ...
Background:
Ketone bodies (KB) might act as potential metabolic modulators besides serving as energy substrates. Bariatric metabolic surgery (BMS) offers a unique opportunity to study nutritional ketosis, as acute postoperative caloric restriction leads to increased lipolysis and circulating free fatty acids.
Aim:
To characterize the relationship between KB production, weight loss (WL) and metabolic changes following BMS.
Methods:
For this retrospective study we enrolled male and female subjects aged 18-65 years who underwent BMS at a single Institution. Data on demographics, anthropometrics, body composition, laboratory values and urinary KB were collected.
Results:
Thirty-nine patients had data available for analyses [74.4% women, mean age 46.5 ± 9.0 years, median body mass index 41.0 (38.5; 45.4) kg/m2, fat mass 45.2% ± 6.2%, 23.1% had diabetes, 43.6% arterial hypertension and 74.4% liver steatosis]. At 46.0 ± 13.6 d post-surgery, subjects had lost 12.0% ± 3.6% of pre-operative weight. Sixty-nine percent developed ketonuria. Those with nutritional ketosis were significantly younger [42.9 (37.6; 50.7) years vs 51.9 (48.3; 59.9) years, P = 0.018], and had significantly lower fasting glucose [89.5 (82.5; 96.3) mg/dL vs 96.0 (91.0; 105.3) mg/dL, P = 0.025] and triglyceride levels [108.0 (84.5; 152.5) mg/dL vs 152.0 (124.0; 186.0) mg/dL, P = 0.045] vs those with ketosis. At 6 mo, percent WL was greater in those with postoperative ketosis (-27.5% ± 5.1% vs 23.8% ± 4.3%, P = 0.035). Urinary KBs correlated with percent WL at 6 and 12 mo. Other metabolic changes were similar.
Conclusion:
Our data support the hypothesis that subjects with worse metabolic status have reduced ketogenic capacity and, thereby, exhibit a lower WL following BMS.
... One concern of KDs is the potential loss of FFM. It seems that in an untrained population, the amount of FFM loss is slightly higher following KDs compared to non-KD (Brehm et al. 2005;Noakes et al. 2006;Tinsley and Willoughby 2016). In our analysis of resistance-trained populations, FFM decreased significantly in individuals assigned to a KD as compared to non-KD. ...
ABSTRACT: We evaluated the effects of ketogenic diets (KDs) on body mass (BM), fat mass (FM), fat-free mass (FFM), body mass index (BMI), and body fat percentage (BFP) compared to non-KDs in individuals performing resistance training (RT). Online electronic databases including PubMed, the Cochrane Library, Web of Science, Embase, SCOPUS, and Ovid were searched to identify initial studies until February 2021. Data were pooled using both fixed and random-effects methods and were expressed as weighted mean difference (WMD) and 95% confidence intervals (CI). Out of 1372 studies, 13 randomized controlled trials (RCTs) that enrolled 244 volunteers were included. The pooled results demonstrated that KDs significantly decreased BM [(WMD ¼ À3.67 kg; 95% CI: À4.44, À2.90, p < 0.001)], FM [(WMD ¼ À2.21 kg; 95% CI: À3.09, À1.34, p < 0.001)], FFM [(WMD ¼ À1.26 kg; 95% CI: À1.82, À0.70, p < 0.001)], BMI [(WMD ¼ À1.37 kg.m À2 ; 95% CI: À2.14, À0.59, p ¼ 0.022)], and BFP [(WMD ¼ À2.27%; 95% CI: À3.63, À0.90, p ¼ 0.001)] compared to non-KDs. We observed beneficial effects of KDs compared to non-KDs on BM and body fat (both FM and BFP) in individuals performing RT. However, adherence to KDs may have a negative effect on FFM, which is not ameliorated by the addition of RT.
... As discussed earlier, the magnitude of cumulative exposure to obesogenic conditions only partially accounts for obesity risk (Sluyter et al., 2013;Willyard, 2014). There are large individual differences in susceptibility for weight gain and fat mass accretion upon exposure to an identical degree of excess energy intake (Brehm et al., 2005;Warwick and Schiffman, 1992). Furthermore, currently-identified genetic variants account for less than 5% of variation in BMI (Locke et al., 2015;Speliotes et al., 2010). ...
Childhood obesity constitutes a major global public health challenge. A substantial body of evidence suggests that conditions and states experienced by the embryo/fetus in utero can result in structural and functional changes in cells, tissues, organ systems and homeostatic set points related to obesity. Furthermore, growing evidence suggests that maternal conditions and states experienced prior to conception, such as stress, obesity and metabolic dysfunction, may spill over into pregnancy and influence those key aspects of gestational biology that program offspring obesity risk. In this narrative review, we advance a novel hypothesis and life-span framework to propose that maternal exposure to childhood maltreatment may constitute an important and as-yet-underappreciated risk factor implicated in developmental programming of offspring obesity risk via the long-term psychological, biological and behavioral sequelae of childhood maltreatment exposure. In this context, our framework considers the key role of maternal-placental-fetal endocrine, immune and metabolic pathways and also other processes including epigenetics, oocyte mitochondrial biology, and the maternal and infant microbiomes. Finally, our paper discusses future research directions required to elucidate the nature and mechanisms of the intergenerational transmission of the effects of maternal childhood maltreatment on offspring obesity risk.
... All but three (1,50,53) have found a modest but significant reduction in BM following a ketogenic as compared to a control diet even though subjects had a normal weight to begin with. The average weight loss was approximately 2 kg, which is much less than what was found with obese subjects (i.e., 5-10 kg) (13,16,56,57). This magnitude of weight loss may seem small but can be crucial in weight sensitive sports especially if performance is maintained or improved. ...
Ketogenic diets (KDs) have received increasing attention among athletes and physically active individuals. However, the question as to whether and how the diet could benefit this healthy cohort remains unclear.
Purpose: This study was designed to systematically review the existing evidence concerning the effect of KDs on body composition, aerobic and anaerobic capacity, muscle development, and sports performance in normal-weight individuals including athletes.
Methods: A systematic search of English literature was conducted through electronic databases including PubMed, EBSCOhost, and Google Scholar. Upon the use of search criteria, 23 full-text original human studies involving non-obese participants were included in this review. For more stratified and focused analysis, these articles were further categorized based on the outcomes being examined including 1) body mass (BM) and %fat, 2) substrate utilization, 3) blood substrate and hormonal responses, 4) aerobic capacity and endurance performance, and 5) strength, power, and anaerobic capacity.
Results: Our review indicates that a non-calorie-restricted KD carried out for ≥3 weeks can produce a modest reduction in BM and %fat, while maintaining fat-free mass. This diet leads to augmented use of fat as fuel, but this adaptation doesn’t seem to improve endurance performance. Additionally, ad libitum KDs combined with resistance training will pose no harm to developing strength and power, especially when protein intake is increased modestly.
Conclusions: It appears that a non-calorie-restricted KD provides minimal ergogenic benefits in normal-weight individuals including athletes, but can be used for optimizing BM and body composition without compromising aerobic and anaerobic performance.
• Key teaching points
• Ketogenic diets have received increasing attention among athletes and physically active individuals.
• It remains elusive as to whether ketogenic diets could confer ergogenic benefits for those who are normal weight but want to use the diet to improve fitness and performance.
• An interesting dilemma exists in that ketogenic diets can reduce body mass and %fat and increase fat oxidation, but they can also decrease glycogen stores and limit sports performance.
• This review concludes that a non-calorie-restricted ketogenic diet provides minimal ergogenic benefits in normal-weight individuals, but can be used to optimize body mass and composition without compromising athletic performance.
• This finding can be important for esthetic or weight-sensitive athletes because the diet may allow them to reach a target body mass without having to sacrifice athletic performance.
• The ketogenic diet-induced metabolic adaptations require a state of ketosis, and thus caution should be taken because an excessive increase in ketone bodies can be detrimental to health.
... This clearly broadens the perspective of the problem. We live in a very "obesogenic" environment and patients are regarded as victims, while they are often unaware of how their own behavior contributes to imminent diseases [6]. And although self-responsible, we are unable to readjust our lifestyle and simply allow the food-, alcohol-, and tobacco industries to fuel this "obesogenic" world. ...
... Our hypothesis is supported by some lines of evidence, but there are contradictory findings due to a lack of studies analyzing the effects of the KD (with and without RT protocol) on FM, VAT and muscle hypertrophy. Human Data are means ± SD; Greenhouse-Geisser univariate p-levels are presented for each variable; p < 0.05 is considered significant; (*) denotes a significant difference from baseline; ES Effect Size (Cohen's d), BW Total body weight, FM Fat mass, VAT Visceral adipose tissue, LBM lean body mass studies have reported a reduction in FM during and after KD, but with a concomitant loss of of LBM [38][39][40][41][42][43][44]. For example, Gomez-Arbelaez [45], found that a low-calorie KD (starting in the initial phases with ≈600-800 kcal per day and following the PNK® method) resulted in a decrease in VAT, according to a follow-up study performed over 4 months. ...
Abstract Background Ketogenic diets (KD) have become a popular method of promoting weight loss. More recently, some have recommended that athletes adhere to ketogenic diets in order to optimize changes in body composition during training. This study evaluated the efficacy of an 8-week ketogenic diet (KD) during energy surplus and resistance training (RT) protocol on body composition in trained men. Methods Twenty-four healthy men (age 30 ± 4.7 years; weight 76.7 ± 8.2 kg; height 174.3 ± 19.7 cm) performed an 8-week RT program. Participants were randomly assigned to a KD group (n = 9), non-KD group (n = 10, NKD), and control group (n = 5, CG) in hyperenergetic condition. Body composition changes were measured by dual energy X-ray absorptiometry (DXA). Compliance with the ketosis state was monitored by measuring urinary ketones weekly. Data were analyzed using a univariate, multivariate and repeated measures general linear model (GLM) statistics. Results There was a significant reduction in fat mass (mean change, 95% CI; p-value; Cohen’s d effect size [ES]; − 0.8 [− 1.6, − 0.1] kg; p 0.05; ES = − 0.12, respectively) or visceral adipose tissue (− 33.8 [− 90.4, 22.8]; p > 0.5; ES = − 0.17 and 1.7 [− 133.3, 136.7]; p > 0.05; ES = 0.01, respectively). No significant increases were observed in total body weight (− 0.9 [− 2.3, 0.6]; p > 0.05; ES = [− 0.18]) and muscle mass (− 0.1 [− 1.1,1.0]; p > 0,05; ES = − 0.04) in the KD group, but the NKD group showed increases in these parameters (0.9 [0.3, 1.5] kg; p 0.05; ES = 0.26, respectively) in the CG. Conclusion Our results suggest that a KD might be an alternative dietary approach to decrease fat mass and visceral adipose tissue without decreasing lean body mass; however, it might not be useful to increase muscle mass during positive energy balance in men undergoing RT for 8 weeks.
... For instance, the higher 3-HB observed in the treatment group than in the control group is consistent with previous studies on weight loss. 32,33 High circulating levels of ketone bodies are observed under energyrestricted metabolic states caused by fasting and caloric restriction, through increased lipolysis of fatty acids in liver mitochondria. 34 Therefore, the increase of 3-HB in treatment may reflect energy homeostasis through increased lipid oxidation. ...
Little is known regarding metabolic benefits of weight loss (WL) on the metabolically healthy obese (MHO) patients. We aimed to examine the impact of a lifestyle weight loss (LWL) treatment on the plasma metabolomic profile in MHO individuals. Plasma samples from 57 MHO women allocated to an intensive LWL treatment group (TG, hypocaloric Mediterranean diet and regular physical activity, n = 30) or to a control group (CG, general recommendations of a healthy diet and physical activity, n = 27) were analysed using an untargeted 1H-NMR metabolomics approach at baseline, after 3 months (intervention) and 12 months (follow-up). The impact of the LWL intervention on plasma metabolome was statistically significant at 3 months but not at follow-up, and included higher levels of formate and phosphocreatine, and lower levels of LDL/VLDL (signals) and trimethylamine in the TG. These metabolites were also correlated with WL. Higher myo-inositol, methylguanidine and 3-hydroxybutyrate, and lower proline were also found in the TG; and higher levels of hippurate and asparagine, and lower levels of 2-hydroxybutyrate and creatine, were associated with WL. The current findings suggest that an intensive LWL treatment, and the consequent WL, leads to an improved plasma metabolic profile in MHO women through its impact on energy, amino acid, lipoprotein and microbial metabolism.
... Indeed, we have observed improvements of ∼25% in clamp-and OGTT-derived measures of insulin sensitivity with as little as 7 days of moderate intensity aerobic exercise (Kirwan, Solomon, Wojta, Staten, & Holloszy, 2009). However, these interventions lack a resistance training component, and this is particularly important where weight loss is accompanied by a loss of lean tissue (Baba et al., 1999;Brehm et al., 2005;Saris et al., 2000;Solomon et al., 2010). Increasing recognition of the role of lean mass in the regulation of blood glucose in T2D (Kirwan, Sacks, & Nieuwoudt, 2017;Srikanthan & Karlamangla, 2011) has prompted the American Diabetes Association to add 2-3 days of resistance training per week to their physical activity recommendations (Colberg et al., 2016). ...
Aim:
Functional high intensity training (F-HIT) is a novel fitness paradigm that integrates simultaneous aerobic and resistance training in sets of constantly varied movements, based on real-world situational exercises, performed at high intensity in workouts that range from ∼8-20 min/session. We hypothesized that F-HIT would be an effective exercise mode for reducing insulin resistance in type 2 diabetes (T2D).
Methods:
We recruited 13 overweight/obese adults (5 males, 8 females; 53 ± 7 years; BMI 34.5 ± 3.6 kg•m-2 , Mean ± SD) with T2D to participate in a 6 week (3d/wk) supervised F-HIT program. An oral glucose tolerance test was used to derive measures of insulin sensitivity.
Results:
F-HIT significantly reduced fat mass (43.8 ± 83.8 vs 41.6 ± 7.9 kg; P < 0.01), diastolic blood pressure (80.2 ± 7.1 vs 74.5 ± 5.8; P < 0.01), blood lipids (triglyceride and VLDL, both P < 0.05) and metabolic syndrome z-score (6.4 ± 4.5 vs -0.2 ± 5.2 AU; P < 0.001), and increased basal fat oxidation (FOX: 0.08 ± 0.03 vs 0.10 ± 0.04 g•min-1 ; P = 0.05), and HMW adiponectin (214.4 ± 88.9 vs 288.8 ± 127.4 ng•mL-1 ; P < 0.01). Importantly, F-HIT also increased insulin sensitivity (0.037 ± 0.010 vs 0.042 ± 0.010 AU; P < 0.05). Increases in HMW adiponectin and FOX correlated with the change in insulin sensitivity (rho: 0.75; P < 0.05, rho: 0.81; P < 0.01, respectively). Compliance with the training program was > 95% and no injuries or adverse events were reported.
Conclusion:
These data suggest that F-HIT may be an effective exercise mode for managing T2D. The increase in insulin sensitivity addresses a key defect in T2D and is consistent with improvements observed after more traditional aerobic exercise programs in overweight/obese adults with T2D. This article is protected by copyright. All rights reserved.
... A total of 4877 articles were retrieved: 989 from Medline, 2324 from Embase and 1564 from the Cochrane trial register. Following first and second pass screening, twenty studies were eligible for inclusion, resulting in 2106 participants for the metaanalysis (28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47) . Details for the screening steps and reasons for exclusion are shown in Fig. 1. ...
Randomised controlled trials comparing low- v. high-fat diets on cardiometabolic risk factors in people with overweight or obesity have shown inconsistent results, which may be due to the mixed metabolic status of people with excess adiposity. The role of dietary fat manipulation in modifying cardiometabolic indicators in people with overweight or obese without metabolic disturbance is unclear. Thus, meta-analysis was conducted to compare low- v. high-fat diets on cardiometabolic indicators in people who are overweight or obese without metabolic disturbance in the present study. Databases were searched until October 2016. The pooled effects of outcomes with heterogeneity were calculated with a random-effects model, heterogeneities were analysed by subgroup and meta-regression. As a result, twenty studies with 2106 participants were included in the meta-analysis. Total cholesterol and LDL-cholesterol levels were lower following low-fat diets compared with high-fat diets: weighted mean difference (WMD) was −7·05 mg/dl (−0·18 mmol/l; 95 % CI −11·30, −2·80; P =0·001) and −4·41 mg/dl (−0·11 mmol/l; 95 % CI −7·81, −1·00; P =0·011), respectively. Conversely, significant higher level of TAG (WMD: 11·68 mg/dl (0·13 mmol/l), 95 % CI 5·90, 17·45; P <0·001) and lower level of HDL-cholesterol (WMD: −2·57 mg/dl (−0·07 mmol/l); 95 % CI −3·85, −1·28; P <0·001) were found following low-fat diets compared with high-fat diets. In conclusion, dietary fat manipulation has a significant influence on blood lipid levels in people with overweight or obesity without metabolic disturbances.
... Both groups exhibited a decrease in resting metabolic rate. Once again, FFM significantly decreased in both groups (-3.34 and -1.94 kg, respectively) (Brehm et al., 2005). ...
The hypertrophy range (8-12 repetitions at 70-85% one-repetition maximum (1RM)) has long been considered the optimal resistance training protocol for the development of fat-free mass (FFM). Recent investigations have hypothesized that lighter repetition zones (over 12 repetitions and less than 67% 1RM) are as effective as heavier loads for the development of FFM. The purpose of this investigation was to determine whether local muscular endurance workouts could sustain and further increase FFM following a program emphasizing the hypertrophy zone. Methods: Healthy, untrained subjects (36 men and 27 women, ages 23 ± 3) completed 96 resistance training workouts. After baseline testing (T1), testing of body composition (dual-energy x-ray absorptiometry (Lunar Prodigy, Madison, WI)) and performance occurred after every 32 workouts (at T2, T3, and T4). In the first block of 32 workouts, 2 of every 3 workouts emphasized the hypertrophy zone and 1/3 emphasized the strength zone (3-7 repetitions at 83 to 93% 1RM). Of the last 32 workouts, 28% of the workouts were in the hypertrophy zone, 47% in the strength zone, and 1/4 in the local muscular endurance zone. Results: FFM significantly increased from T1 (49.8 ± 10.0 kg)until T3 (52.6 ± 10.5kg), at which point it significantly decreased to T4 (52.2 ± 10.7kg). Squat strength and bone mineral density significantly increased, but vertical jump power production did not continue to increase between T3 and T4. Discussion: This investigation suggests that replacing hypertrophy-zone workouts with endurance zone workouts prevents further increases in FFM and results in a loss of FFM previously gained.
... A total of 1,797 overweight and obese subjects (895 on LoCHO and 902 on LoFAT diets) were included. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Of 17 trials, 11 provided information for completers and 6 for ITT analyses. (Fig 1 and Tables 1 and 2) No trial that focused on patients with type 2 diabetes met criteria for inclusion in this analysis. ...
Reduced calorie, low fat diet is currently recommended diet for overweight and obese adults. Prior data suggest that low carbohydrate diets may also be a viable option for those who are overweight and obese.Compare the effects of low carbohydrate versus low fats diet on weight and atherosclerotic cardiovascular disease risk in overweight and obese patients.Systematic literature review via PubMed (1966-2014).Randomized controlled trials with ≥8 weeks follow up, comparing low carbohydrate (≤120gm carbohydrates/day) and low fat diet (≤30% energy from fat/day).Data were extracted and prepared for analysis using double data entry. Prior to identification of candidate publications, the outcomes of change in weight and metabolic factors were selected as defined by Cochrane Collaboration. Assessment of the effects of diets on predicted risk of atherosclerotic cardiovascular disease risk was added during the data collection phase.1797 patients were included from 17 trials with 98%.Lack of patient-level data and heterogeneity in dropout rates and outcomes reported.This trial-level meta-analysis of randomized controlled trials comparing LoCHO diets with LoFAT diets in strictly adherent populations demonstrates that each diet was associated with significant weight loss and reduction in predicted risk of ASCVD events. However, LoCHO diet was associated with modest but significantly greater improvements in weight loss and predicted ASCVD risk in studies from 8 weeks to 24 months in duration. These results suggest that future evaluations of dietary guidelines should consider low carbohydrate diets as effective and safe intervention for weight management in the overweight and obese, although long-term effects require further investigation.
... The ANGPTL4-gene increases the production of the ANGPTL4 protein, which has great impact on the uptake of fat from the blood stream to the adipose tissue by inhibition of lipoprotein lipase, but which recently also was shown to inhibit the pancreatic lipase in the gut [19], thus potentially also reducing the uptake of dietary fat. In addition, milk Raw milk (2) protein, especially whey, may regulate body weight: firstly, whey increases satiety and reduces energy intake [20]; secondly, whey enhances the thermic effect of food, resulting in higher post-meal energy expenditure [21]; thirdly, whey suppresses lipogenic enzyme in the adipose tissue [22]. In addition, fermented dairy products have been shown to result in increased gut bacterial content in humans [23], which must be considered an intriguing finding as there is increasing attention to the role of gut microbiota on the development of obesity [24]. ...
Dairy products are an important component in the Western diet and represent a valuable source of nutrients for humans. However, a reliable dairy intake assessment in nutrition research is crucial to correctly elucidate the link between dairy intake and human health. Metabolomics is considered a potential tool for assessment of dietary intake instead of traditional methods, such as food frequency questionnaires, food records, and 24-h recalls. Metabolomics has been successfully applied to discriminate between consumption of different dairy products under different experimental conditions. Moreover, potential metabolites related to dairy intake were identified, although these metabolites need to be further validated in other intervention studies before they can be used as valid biomarkers of dairy consumption. Therefore, this review provides an overview of metabolomics for assessment of dairy intake in order to better clarify the role of dairy products in human nutrition and health.
... Plus certainement, les propriétés satiétogènes des protéines limiteraient les prises alimentaires(Brehm et al., 2005;Nickols-Richardson et al., 2005;Schoeller & Buchholz, 2005).Un autre essai clinique a comparé l'efficacité de quatre régimes plus ou moins riches en glucides chez des femmes en surpoids ou obèses(Gardner et al., 2007). Le régime le plus par ailleurs les mêmes effets métaboliques favorables. ...
The Longitudinal Study on Health and Diet (ELPAS) was designed in 2001. It aimed at assessing in children and adults feasibility and clinical efficacy of isocaloric macronutrient modulations (decreases in fat and simple sugar intakes and increase in complex carbohydrate intake). This is a randomized controlled dietary modification trial, which was carried out in 2005/2006 in 1013 Parisian families. Several studies were performed prior to the intervention:
... Several studies agree that the decrease in resting energy expenditure (REE) which accompanies weight loss is independent of diet macronutrient composition. Reduction in REE is expected to occur with the loss of both fat mass and fat free mass (FFM) (20). As REE depends hugely on the amount of FFM, then preservation of FFM, which can take place on energy restricted high-protein diets, can reduce the fall in REE. ...
This review examines the effects of low-carbohydrate, high-protein diets (LCHO) (<150g carbohydrate/d) on glycaemia and cardiovascular risk, energy expenditure, appetite and satiety, liver and kidney function, bone metabolism, and possible adverse effects in type 2 diabetes mellitus (T2DM). At this stage, there is evidence to suggest that the use of lower carbohydrate diets improves glycaemia, cardiovascular risk and liver function in patients with T2DM and broadens patient choice as LCHOs provide an alternative to the standard dietary interventions. However, there is still a lack of evidence for the use of these approaches in the longer term.
... Despite anecdotal reports, this theory has not been proven in clinical trials. Brehm et al., (2005) reported no significant differences in postprandial thermogenesis when comparing the two approaches, whilst Foreyt et al., (2009) assert that the amount of energy lost through excretion of ketone bodies in the urine cannot account for more than a few calories per day. A meta-analysis conducted by Bravata et al., (2003) concluded that weight loss with a low-carbohydrate diet occurs due to a reduction in calories rather than other metabolic factors. ...
Obesity in women of reproductive age is common. Emerging evidence suggests that maternal obesity not only increases the risk of adverse pregnancy outcomes but also has an enduring impact on the metabolic health of the offspring. Given this, management of obesity prior to pregnancy is critically important. Almost all international guidelines suggest that women with obesity should aim to achieve weight loss prior to pregnancy. However, current pre-conception weight loss therapies are sub-optimal. Lifestyle modification typically results in modest weight loss. This may assist fertility but does not alter pregnancy outcomes. Bariatric surgery results in substantial weight loss, which improves pregnancy outcomes for the mother but may be harmful to the offspring. Alternative approaches to the management of obesity in women planning pregnancy are needed. Very low energy diets (VLEDs) have been proposed as a possible tool to assist women with obesity achieve weight loss prior to conception. While VLEDs can induce substantial and rapid weight loss, there are concerns about the impact of rapid weight loss on maternal nutrition prior to pregnancy and about inadvertent exposure of the early fetus to ketosis. The purpose of this review is to examine the existing literature regarding the safety and efficacy of a preconception VLED program as a tool to achieve substantial weight loss in women with obesity.
Objectives:
Dietary therapy may improve glucose and lipid metabolism function in women. However, there is no systematic review to investigate the association between metabolic effects and different dietary interventions in obese women. The main purpose of this study is to summarize the current literature and investigate whether different dietary interventions have an effect on glucose and metabolic indicators of overweight or obese women.
Methods:
We conducted a scoping review of randomized controlled trial (RCT) studies from 1991 to 2022 by adopting a systematic review and meta-analysis. The database includes Google Scholar, PubMed, Embase and Web of Science. Literature screening, data extraction, and quality assessment were independently completed by 2 researchers. Meta-analysis was performed with RevMan.
Results:
Twelve articles were extracted and the meta-analysis results showed that the mean difference of metabolic indexes of obese women before and after dietary intervention, including fasting glucose, fasting insulin, HOMA-IR (Homeostasis model assessment-insulin resistance), TG (triglyceride), TC (total cholesterol), LDL-C (low-density lipoprotein cholesterol), HDL-C (high-density lipoprotein cholesterol) are -0.13 [-0.15, -0.10], -2.41 [-3.44, -1.38], -0.13 [-0.15, -0.10], -21.71 [-24.19, -19.22], -21.71 [-24.19, -19.22], -13.29 [-17.86, -8.72], 3.31 [2.22, 4.40], respectively.
Conclusions:
Different dietary interventions benefit glucose and lipid metabolism of overweight or obese women. Further study is needed to determine which specific dietary effects have the greatest effect on improving metabolic indicators.
A dysregulation between energy intake (EI) and energy expenditure (EE), the two components of the energy balance equation, is one of the mechanisms responsible for the development of obesity. Conservation of energy equilibrium is deemed a dynamic process and alterations of one component (energy intake or energy expenditure) lead to biological and/or behavioral compensatory changes in the counterpart. The interplay between energy demand and caloric intake appears designed to guarantee an adequate fuel supply in variable life contexts. In the past decades, researchers focused their attention on finding efficient strategies to fight the obesity pandemic. The ketogenic or “keto” diet (KD) gained substantial consideration as a potential weight-loss strategy, whereby the concentration of blood ketones (acetoacetate, 3-β-hydroxybutyrate, and acetone) increases as a result of increased fatty acid breakdown and the activity of ketogenic enzymes. It has been hypothesized that during the first phase of KDs when glucose utilization is still prevalent, an increase in EE may occur, due to increased hepatic oxygen consumption for gluconeogenesis and for triglyceride-fatty acid recycling. Later, a decrease in 24-h EE may ensue due to the slowing of gluconeogenesis and increase in fatty acid oxidation, with a reduction of the respiratory quotient and possibly the direct action of additional hormonal signals.
Dietary restriction of carbohydrate has been demonstrated to be beneficial for nervous system dysfunction in animal models and may be beneficial for human chronic pain. The purpose of this review is to assess the impact of a low-carbohydrate/ketogenic diet on the adult nervous system function and inflammatory biomarkers to inform nutritional research for chronic pain. An electronic data base search was carried out in May 2021. Publications were screened for prospective research with dietary carbohydrate intake <130g/day and duration of ≥2 weeks. Studies were categorised into those reporting adult neurological outcomes to be extracted for analysis and those reporting other adult research outcomes Both groups were screened again for reported inflammatory biomarkers. From 1548 studies there were 847 studies included. Sixty-four reported neurological outcomes with 83% showing improvement. Five hundred and twenty-three studies had a different research focus (metabolic n=394, sport/performance n=51, cancer n=33, general n=30, neurological with non-neuro outcomes n=12, or gastrointestinal n=4). The second screen identified 63 studies reporting on inflammatory biomarkers with 71% reporting a reduction in inflammation. The overall results suggest a favourable outcome on the nervous system and inflammatory biomarkers from a reduction in dietary carbohydrates. Both nervous system sensitisation and inflammation occur in chronic pain and the results from this review indicate it may be improved by low-carbohydrate nutritional therapy. More clinical trials within this population are required to build on the few human trials that have been done.
Background:
Debates on effective and safe diets for managing obesity in adults are ongoing. Low-carbohydrate weight-reducing diets (also known as 'low-carb diets') continue to be widely promoted, marketed and commercialised as being more effective for weight loss, and healthier, than 'balanced'-carbohydrate weight-reducing diets.
Objectives:
To compare the effects of low-carbohydrate weight-reducing diets to weight-reducing diets with balanced ranges of carbohydrates, in relation to changes in weight and cardiovascular risk, in overweight and obese adults without and with type 2 diabetes mellitus (T2DM).
Search methods:
We searched MEDLINE (PubMed), Embase (Ovid), the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science Core Collection (Clarivate Analytics), ClinicalTrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) up to 25 June 2021, and screened reference lists of included trials and relevant systematic reviews. Language or publication restrictions were not applied.
Selection criteria:
We included randomised controlled trials (RCTs) in adults (18 years+) who were overweight or living with obesity, without or with T2DM, and without or with cardiovascular conditions or risk factors. Trials had to compare low-carbohydrate weight-reducing diets to balanced-carbohydrate (45% to 65% of total energy (TE)) weight-reducing diets, have a weight-reducing phase of 2 weeks or longer and be explicitly implemented for the primary purpose of reducing weight, with or without advice to restrict energy intake. DATA COLLECTION AND ANALYSIS: Two review authors independently screened titles and abstracts and full-text articles to determine eligibility; and independently extracted data, assessed risk of bias using RoB 2 and assessed the certainty of the evidence using GRADE. We stratified analyses by participants without and with T2DM, and by diets with weight-reducing phases only and those with weight-reducing phases followed by weight-maintenance phases. Primary outcomes were change in body weight (kg) and the number of participants per group with weight loss of at least 5%, assessed at short- (three months to < 12 months) and long-term (≥ 12 months) follow-up.
Main results:
We included 61 parallel-arm RCTs that randomised 6925 participants to either low-carbohydrate or balanced-carbohydrate weight-reducing diets. All trials were conducted in high-income countries except for one in China. Most participants (n = 5118 randomised) did not have T2DM. Mean baseline weight across trials was 95 kg (range 66 to 132 kg). Participants with T2DM were older (mean 57 years, range 50 to 65) than those without T2DM (mean 45 years, range 22 to 62). Most trials included men and women (42/61; 3/19 men only; 16/19 women only), and people without baseline cardiovascular conditions, risk factors or events (36/61). Mean baseline diastolic blood pressure (DBP) and low-density lipoprotein (LDL) cholesterol across trials were within normal ranges. The longest weight-reducing phase of diets was two years in participants without and with T2DM. Evidence from studies with weight-reducing phases followed by weight-maintenance phases was limited. Most trials investigated low-carbohydrate diets (> 50 g to 150 g per day or < 45% of TE; n = 42), followed by very low (≤ 50 g per day or < 10% of TE; n = 14), and then incremental increases from very low to low (n = 5). The most common diets compared were low-carbohydrate, balanced-fat (20 to 35% of TE) and high-protein (> 20% of TE) treatment diets versus control diets balanced for the three macronutrients (24/61). In most trials (45/61) the energy prescription or approach used to restrict energy intake was similar in both groups. We assessed the overall risk of bias of outcomes across trials as predominantly high, mostly from bias due to missing outcome data. Using GRADE, we assessed the certainty of evidence as moderate to very low across outcomes. Participants without and with T2DM lost weight when following weight-reducing phases of both diets at the short (range: 12.2 to 0.33 kg) and long term (range: 13.1 to 1.7 kg). In overweight and obese participants without T2DM: low-carbohydrate weight-reducing diets compared to balanced-carbohydrate weight-reducing diets (weight-reducing phases only) probably result in little to no difference in change in body weight over three to 8.5 months (mean difference (MD) -1.07 kg, (95% confidence interval (CI) -1.55 to -0.59, I2 = 51%, 3286 participants, 37 RCTs, moderate-certainty evidence) and over one to two years (MD -0.93 kg, 95% CI -1.81 to -0.04, I2 = 40%, 1805 participants, 14 RCTs, moderate-certainty evidence); as well as change in DBP and LDL cholesterol over one to two years. The evidence is very uncertain about whether there is a difference in the number of participants per group with weight loss of at least 5% at one year (risk ratio (RR) 1.11, 95% CI 0.94 to 1.31, I2 = 17%, 137 participants, 2 RCTs, very low-certainty evidence). In overweight and obese participants with T2DM: low-carbohydrate weight-reducing diets compared to balanced-carbohydrate weight-reducing diets (weight-reducing phases only) probably result in little to no difference in change in body weight over three to six months (MD -1.26 kg, 95% CI -2.44 to -0.09, I2 = 47%, 1114 participants, 14 RCTs, moderate-certainty evidence) and over one to two years (MD -0.33 kg, 95% CI -2.13 to 1.46, I2 = 10%, 813 participants, 7 RCTs, moderate-certainty evidence); as well in change in DBP, HbA1c and LDL cholesterol over 1 to 2 years. The evidence is very uncertain about whether there is a difference in the number of participants per group with weight loss of at least 5% at one to two years (RR 0.90, 95% CI 0.68 to 1.20, I2 = 0%, 106 participants, 2 RCTs, very low-certainty evidence). Evidence on participant-reported adverse effects was limited, and we could not draw any conclusions about these. AUTHORS' CONCLUSIONS: There is probably little to no difference in weight reduction and changes in cardiovascular risk factors up to two years' follow-up, when overweight and obese participants without and with T2DM are randomised to either low-carbohydrate or balanced-carbohydrate weight-reducing diets.
Low-carbohydrate diets (LChD) have become very popular among the general population. These diets have been used to lose body weight and to ameliorate various abnormalities like diabetes, nonalcoholic fatty liver disease, polycystic ovary syndrome, narcolepsy, epilepsy, and others. Reports suggest that body weight reduction and glycemic control could be attained while following LChD. However, these advantages are more notably found in short periods of time consuming an LChD. Indeed, the safety and efficacy of the latter diets in the long term have not been sufficiently explored. In contrast to what has been proposed, other mentioned pathologies are not improved or are even worsened by carbohydrate restriction. Therefore, the aim of this review is to define the concept of LChD and to explain their clinical effects in the short and long term, their influence on metabolism, and the opinion of nutrition or health authorities. Finally, evincing the research gaps of LChD that are here exposed will later allow us to reach a consensus with regard to their utilization.
Obesity remains a serious relevant public health concern throughout the world despite related countermeasures being well understood (i.e., mainly physical activity and an adjusted diet). Among different nutritional approaches, there is a growing interest in ketogenic diets (KDs) to manipulate body mass (BM) and to enhance fat mass (FM) loss. KDs reduce the daily amount of carbohydrate intake drastically. This results in increased fatty acid utilization, leading to an increase in blood ketone bodies (KBs) (acetoacetate [AcAc], 3-β-hydroxybutyrate [BHB], and acetone), and therefore metabolic ketosis. For many years, nutritional intervention studies have focused on reducing dietary fat with little or conflicting positive results over the long-term. Moreover, current nutritional guidelines for athletes propose carbohydrate-based diets to augment muscular adaptations. This review discusses the physiological basis of KDs and their effects on BM reduction and body composition improvements in sedentary individuals combined with different types of exercise (resistance training [RT] or endurance training [ET]) in individuals with obesity and athletes. Ultimately, we discuss the strengths and the weaknesses of these nutritional interventions together with precautionary measures that should be observed in both individuals with obesity and athletic populations. A literature search from 1921 to April 2021 using MEDLINE, GOOGLE SCHOLAR, PUBMED, WEB OF SCIENCE, SCOPUS, and SPORTDISCUS databases were used to identify relevant studies. In summary, based on the current evidence, KDs are an efficient method to reduce BM and body fat in both individuals with obesity and athletes. However, these positive impacts are mainly because of the appetite suppressive effects of KDs, which can decrease daily calorie intake. Therefore, KDs do not have any superior benefits to non-KDs in BM and body fat loss in individuals with obesity and athletic populations in an isocaloric situation. In sedentary individuals with obesity, it seems that fat-free mass (FFM) changes appear to be as great, if not greater, than decreases following a low-fat diet (LFD). In terms of lean mass, it seems that following a KD can cause FFM loss in resistance-trained individuals. In contrast, the FFM-preserving effects of KDs are more efficient in endurance-trained compared to resistance-trained individuals.
Here, we report on the role of haptoglobin (Hp), whose expression depends on the synthesis of interleukin 6 (IL-6), related to the pathogenesis of multiple sclerosis (MS), as a possible marker of muscle improvement achieved after treatment with the polyphenol epigallocatechin gallate (EGCG) and an increase in the ketone body beta-hydroxybutyrate (BHB) in the blood. After 4 months of intervention with 27 MS patients, we observed that Hp does not significantly increase, alongside a significant decrease in IL-6 and a significant increase in muscle percentage. At the same time, Hp synthesis is considerably and positively correlated with IL-6 both before and after treatment; while this correlation occurs significantly reversed with muscle percentage before treatment, no correlation is evident after the intervention. These results seem to indicate that Hp could be a marker of muscle status and could be a diagnosis tool after therapeutic intervention in MS patients.
The incidence of cardiometabolic diseases, such as obesity, diabetes, and cardiovascular diseases, is constantly rising. Successful lifestyle changes may limit their incidence, which is why researchers focus on the role of nutrition in this context. The outcomes of studies carried out in past decades have influenced dietary guidelines, which primarily recommend reducing saturated fat as a therapeutic approach for cardiovascular disease prevention, while limiting the role of sugar due to its harmful effects. On the other hand, a low-carbohydrate diet (LCD) as a method of treatment remains controversial. A number of studies on the effect of LCDs on patients with type 2 diabetes mellitus proved that it is a safe and effective method of dietary management. As for the risk of cardiovascular diseases, the source of carbohydrates and fats corresponds with the mortality rate and protective effect of plant-derived components. Additionally, some recent studies have focused on the gut microbiota in relation to cardiometabolic diseases and diet as one of the leading factors affecting microbiota composition. Unfortunately, there is still no precise answer to the question of which a single nutrient plays the most important role in reducing cardiometabolic risk, and this review article presents the current state of the knowledge in this field.
Background: Some researchers administer a diet with a higher ratio of protein to carbohydrates (HP) in patients with polycystic ovary syndrome (PCOS), but there is a limited number of dietary interventions compared the effects of an HP diet with a standard protein (SP) diet. Therefore, the aim of this review was to compare the effects of energy-restricted HP diets with those of iso-calorically prescribed SP diets on anthropometric, metabolic, hormonal, and reproductive outcomes in women with PCOS.
Materials and methods: Searches for English-language studies published between 2000 and 2014 were conducted using PubMed, Science Direct, and Scopus databases to identify all randomized controlled trials that compared HP diet with SP diet.
Results: There was no difference in anthropometric outcomes between two different diets. There was no difference in reproductive outcomes between the two dietary treatments. Weight loss decreased testosterone, free testosterone, or FAI (Free Androgen Index) and increased SHBG, independent of prescribed diet. There was no difference in metabolic outcomes between the two dietary treatments. A standard-protein weight-loss diet reduced HDL- cholesterol, while no changes occurred for a high protein weight-loss diet. The high-protein diet reduced total cholesterol to HDL-C ratio. Weight loss, independent of diet composition, decreased fasting insulin, insulin resistance and Improvements in lipid profiles.
Conclusion: High protein diet caused subtle and inconsistent changes in metabolic variables, and weight loss results in clinical benefit, regardless of diet composition, in women with PCOS.
Keyword(s): HIGH PROTEIN DIET, STANDARD DIET, PCOS, FERTILITY, METABOLIC, ANTHROPOMETRIC OUTCOMES
Background:
The rise in obesity has emphasised a focus on lifestyle and dietary habits. We aimed to address the debate between low-carbohydrate and low-fat diets and compare their effects on body weight, low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), total cholesterol, and triglycerides in an adult population.
Method:
Medline and Web of Science were searched for randomised controlled trials (RCTs) comparing low-fat and low-carbohydrate diets up to September 2019. Three independent reviewers extracted data. Risk of bias was assessed using the Cochrane tool. The meta-analysis was stratified by follow-up time using the random-effects models.
Results:
This meta-analysis of 38 studies assessed a total of 6499 adults. At 6-12 months, pooled analyses of mean differences of low-carbohydrate vs. low-fat diets favoured the low-carbohydrate diet for average weight change (mean difference -1.30 kg; 95% CI -2.02 to -0.57), HDL (0.05 mmol/L; 95% CI 0.03 to 0.08), and triglycerides (TG) (-0.10 mmol/L; -0.16 to -0.04), and favoured the low-fat diet for LDL (0.07 mmol/L; 95% CI 0.02 to 0.12) and total cholesterol (0.10 mmol/L; 95% CI 0.02 to 0.18). Conclusion and Relevance: This meta-analysis suggests that low-carbohydrate diets are effective at improving weight loss, HDL and TG lipid profiles. However, this must be balanced with potential consequences of raised LDL and total cholesterol in the long-term.
In the past decades, the ketogenic diet has received scientific interest as a diet which may be beneficial for athletes. We summarize the ketogenic literature and give competitive bodybuilders and physique athletes advice on whether the diet and ketone supplements are suitable for off-season and in-season use.
The diet is effective for fat loss and has a strong hunger-reducing effect. Current evidence suggests it is suboptimal for bulking and gaining lean mass. Upon starting the diet, negative side effects should be expected and prevented by increasing intake of electrolytes, fiber, and water. Exogenous ketones are currently not recommended.
Low-carbohydrate diets (LCDs) often differ in their diet composition, which may lead to conflicting results between randomized controlled trials. Therefore, we aimed to compare the effects of different degrees of carbohydrate (CHO) restriction on cardiometabolic risk markers in humans. The experimental LCDs of 37 human trials were classified as (1) moderate-low CHO diets (<45–40 E%, n = 13), (2) low CHO diets (<40–30 E%, n = 16), and (3) very-low CHO diets (<30–3 E%; n = 8). Summary estimates of weighted mean differences (WMDs) in selected risk markers were calculated using random-effect meta-analyses. Differences between the LCD groups were assessed with univariate meta-regression analyses. Overall, the LCDs resulted in significant weight loss, reduced diastolic blood pressure BP, and increased total cholesterol and high-density lipoprotein cholesterol (HDL-C), without significant differences between the three LCD groups. Higher low-density lipoprotein cholesterol (LDL-C) concentrations were found with the very-low CHO diets compared to the moderate-low CHO diets. Decreases in triacylglycerol (TAG) concentrations were more pronounced with the low and very-low CHO diets, compared to the moderate-low CHO diets. Substitution of CHO by mainly saturated fatty acids (SFAs) increased total cholesterol, LDL-C, and HDL-C concentrations. Except for LDL-C and TAGs, effects were not related to the degree of CHO restriction. Potential effects of nutrient exchanges should be considered when following LCDs.
Background
Maintaining weight loss is difficult, partly as a result of accompanying reductions in fat oxidation. The present study examined fat oxidation [reflected by respiratory exchange ratio (RER)] within an 8‐week, self‐led weight loss intervention. Changes in RER, body fat (BF%) and estimated energy expenditure (EE) were examined.
Methods
Twenty‐two adults [13 females, nine males; mean (SD) age 34.6 (16.5) years; body mass index 32.0 (4.3) kg m⁻²] received a self‐directed workbook; twelve were also randomised to receive a self‐monitoring wrist‐worn device. At weeks 0 and 8, RER (indirect calorimetry), BF% (BodPod) and estimated EE [7‐day physical activity recall (PAR‐EE) were collected. Participants were pooled and paired t‐tests were used to examine changes over time. Correlations explored associations among variables. Participants were then dichotomised into weight loss group (WL) or weight stable/gainers group (WSG) and eating behaviours [Intuitive Eating Scale (IES‐2)] were examined by 2 × 2 repeated measures multivariate analysis of covariance.
Results
There were no significant changes in RER, body fat percentage and PAR‐EE. A significant negative association was found between week 8 PAR‐EE and week 8 RER, as well as between BF% change and RER change. There was a significant time by WL versus WSG group effect of IES‐2 scores, with the WL group self‐reporting significantly increased scores in Eating for Physical Reasons rather than Emotional Reasons (EPR) subscale.
Conclusions
Increased physical activity after an 8‐week weight loss intervention was associated with a higher fasting fat oxidation. Participants who increased EPR scores were more successful in weight loss than those without a change in this subscale.
Macronutrients, carbohydrate, protein, and fat, are required daily to provide energy for growth, maintenance, and repair of body tissues. Consumption of macronutrients for energy is driven by both physiological and psychological needs. The role of diet composition in response to overeating and energy utilization in humans is unclear, especially with severe obesity. While the most clinically significant and relatively sustainable treatment for obesity is weight loss surgery (WLS), weight loss goals may not be achieved without lifestyle changes.
This chapter will examine the role of macronutrients in energy balance and surgical weight loss, the weight loss implications of dietary macronutrient distribution, and dietary intake recommendations for weight loss and weight maintenance.
Over the past decades dietary fat was perceived to be one of the main contributing factors to the development and maintenance of overweight and obesity. However, paradoxically, dietary fat intake has been demonstrated to decline whilst the prevalence of obesity has continued to increase at phenomenal rates. Since obesity is primarily a problem of energy balance, the ideal approach to the treatment and prevention of overweight and obesity would encompass both reductions to total energy intake and increased energy expenditure. Over the past few years, several popular diets dealing with the energy intake aspect of the energy balance equation focused on reducing energy consumption. One of the more recent popular dietary interventions is the use of the low-carbohydrate diet; such diets include the Atkins diet and the South Beach diet. However, these diets have come under immense criticism due to their high-fat content. Yet, consuming a high-fat diet does not inevitably lead to overweight or obesity The current article aims to give a brief outline of the effectiveness of low-carbohydrate diets for weight-loss. Here we propose that even if such dietary interventions are only effective in the short-term we should still consider them a useful tool for the treatment of overweight and obesity for some individuals.
A more comprehensive understanding of the effects of weight loss on the changes in resting energy expenditure (EE) is relevant. A MEDLINE search was performed to identify studies with information relevant to this systematic review. From this search, the mean rate of resting EE decrease relative to weight loss was calculated from 90 available publications. A decrease of resting EE relative to weight loss of-15.4 8.7 kcal kg-1 was observed from 2996 subjects. No sex differences were noted in the overall resting EE decrease relative to weight loss. However, a significant sex differences was seen with pharmacological interventions, which seemed to depress the resting EE relative to weight loss to a greater extent in men than in women (P < 0.05). A greater drop in resting EE relative to weight loss was observed for short interventions (more than 2 but less than 6 weeks) when compared with long interventions (<6 weeks) (–27.7 6.7 vs.-12.8 7.1 kcal kg-1) (P < 0.001). Men and women have a similar decrease in resting EE relative to weight loss except in the case of pharmacological interventions. Short interventions also produced greater resting EE losses relative to weight loss.
First rule of thumb: address the issueAssessmentPast medical historyBiochemical dataMedication useDieting risksThe dietsMedically supervised very low calorie programsProgrammatic dietsEffects of certain diets with medication for weight lossBariatric SurgeryReferences
Obesity is a chronic disease caused by an imbalance of the energy metabolism and related to many other diseases. Many intensive studies aimed to develop more specific, long-lasting and safe slimming protocols have been used new diets that consist low-calorie and different macronutrint composition. When compared to low fat diets, low carbohydrate diets are more effective in improving metabolic syndrome's characteristic specifications such as fasting plasma triglyceride (TG), triglyceride/high density lipoprotein-cholesterol ratio, postprandial lipemia and low density lipoprotein sub-classes. Low carbohydrate diets may induce more weight loss. Because of unmatched energy intake of many studies, it is not clear that whether this effect associated with reduction in energy intake or increase in energy consumption. Some studies showed that there is no difference between low carbohydrate and low fat diets in term of weight loss. In addition, when comparisons made with high carbohydrate in isoenergetic conditions, there is lack of evidence about high fat diets may induce weight gain. Diets that high in protein and low in carbohydrate may support weight loss via increasing the loss of fat mass and conserving fat free mass. While studies of prolonged use of moderate protein diets are not available, short-term studies report beneficial effects associated with increased satiety, increased thermogenesis, sparing of muscle protein loss and enhanced glycemic control. In this review, effects of diets that differed in macronutrient content on weight loss comparatively evaluated.
Background: The growing epidemics of obesity and metabolic syndrome (MetS) have been accompanied with dietary fat restriction and carbohydrate elevation. We evaluated the efficacy of moderately-restricted carbohydrate diet on features of the MetS in women.
Methods: In a randomized cross-over clinical trial, 30 overweight or obese (Body mass index > 25 kg/m2) women with the MetS were enrolled. Subjects were randomly allocated to receive either a high-carbohydrate (HC) (60-65% carbohydrates, 20-25% fats) or a moderately-restricted carbohydrate (MRC) (43-47% carbohydrate, 36-40% fats) diet. Diets were continued for 6 weeks followed by a 2-week washout period. Anthropometrics, blood pressure and biochemical variables were measured before and after each intervention period.
Findings: Despite similar weight loss in both diets, the efficacy of MRC diet in reducing waist (-3.9 vs. -2.6 cm; P = 0.07) and hip circumferences (-2.7 vs. -1.5 cm; P = 0.07) was marginally greater compared with HC diet. In contrast to HC diet, MRC diet resulted in favorable changes in serum triglyceride (TG) concentrations (0.13 vs. -31.3 mg/dL; P = 0.07). This was also the case for TG to high density lipoprotein (HDL)-cholesterol ratio (-0.9 vs. -0.1; P = 0.06). The reductions in systolic blood pressure (-8.93 vs. -2.97 mmHg; P = 0.06) and diastolic blood pressure (-12.7 vs. -1.77 mmHg; P = 0.001) by MRC diet were higher than those by HC diet. The prevalence of MetS was significantly decreased only by MRC diet (P = 0.03).
Conclusion: Partial replacement of dietary carbohydrates by unsaturated fats might be recommended as an effective strategy for treatment of MetS.
It has been proposed that a higher protein intake in those with type 2 diabetes mellitus may aid in weight loss, better glycemic control, and a favorable blood lipid profile. It is also suggested that protein may contribute to greater satiety, and hence better compliance to a healthy dietary pattern. This chapter will review the evidence for each of these hypotheses, and consider some of the safety aspects commonly raised in conjunction with higher protein diets.
Trends on nutritional changes occurring in this century in different countries around the world is consequence of a high-fat diet, rich sugar diet and refined foods, and low in complex carbohydrates and fiber, also known as the Western Diet. In association with this nutritional change studies show a progressive decline in physical activity of individuals. Together, the increased availability and consumption of highly palatable and energy diets and decreased energy expenditure could explain the growing incidence of obesity worldwide. Importantly, the increase in the number of obese people has been seen as a public health problem, since obesity is considered an important risk factor for the development of comorbidities such as type 2 diabetes mellitus, dyslipidemia, cardiovascular disease, among others, which are involved with the declining quality of life and increased human morbidity and mortality. For this reason, the development of effective strategies that work in prevention and treatment of excess body weight has been an important challenge facing humanity. Low-calorie diets play a central role in reducing body fat in obese subjects. However, the adaptation to a calorie-restricted diet is characterized by metabolic, endocrine, and immunologic changes. In humans, the weight loss induced by lower food intake was associated with lower risk factors for cardiovascular disease, decreased incidence of type 2 diabetes mellitus and increased life quality. In addition, calorie restriction may be considered a safe method of weight loss, as it reduces fat mass without altering muscle mass. This review aims to discuss the influence of calories on the weight gain / loss, as well as what is currently known about diets composition on body weight.
The importance of monitoring dietary intake within a randomized controlled trial becomes vital to justification of the study outcomes when the study is food-based. A systematic literature review was conducted to determine how dietary assessment methods used to monitor dietary intake are reported and whether assisted technologies are used in conducting such assessments. OVID and ScienceDirect databases 2000-2010 were searched for food-based, parallel, randomized controlled trials conducted with humans using the search terms "clinical trial", "diet$ intervention" AND "diet$ assessment", "diet$ method$", "intake", "diet history", "food record", "food frequency questionnaire", "FFQ", "food diary", "24 hour recall". A total of 1364 abstracts were reviewed and 243 studies identified. The size of the study and country of origin appear to be the two most common predictors of reporting both the dietary assessment method and details of the form of assessment. The journal in which the study is published has no impact. Information technology use may increase in the future allowing other methods and forms of dietary assessment to be used efficiently.
Intense marketing for sugar-sweetened beverages (SSB) along with the human innate preference for sweet taste contributes to the increase in consumption of SSB. It is important to understand the intricacies of dietary intake and global changes to the food supply to understand the complexities facing any intervention promoting water intake. We describe challenges to promote and achieve an increase in water intake and present key findings from a clinical trial examining the effects of substituting water for SSB on triglyceride levels, weight and other cardiometabolic factors in overweight/obese Mexican women.
A randomized trial was conducted in Cuernavaca, Mexico selecting overweight/obese (BMI ≥25 and <39 kg/m(2)) women (18-45 years old), reporting an intake of SSB of at least 250 kcal/day. Women were randomly allocated to the water and education provision (WEP) group (n = 120) or to the education provision (EP) group (n = 120). Repeated 24 h dietary recall questionnaires, anthropometry, and fasting blood levels were collected at baseline and 3, 6, and 9 months following the intervention.
There was no effect of the intervention on triglyceride concentration or on any of the studied outcomes. Post-hoc analyses according to weight at baseline show that triglyceride concentration decreased in obese women. Prevalence of metabolic syndrome after the intervention was lower in obese women from the WEP group.
Water intake was increased but insufficient to achieve complete substitution of SSB, without effects on triglyceride concentration. Post-hoc analyses suggested that interventions lowered triglyceride concentration. Further studies are needed. © 2015 S. Karger AG, Basel.
Context The prevalence of obesity and overweight increased in the United States
between 1978 and 1991. More recent reports have suggested continued increases
but are based on self-reported data.Objective To examine trends and prevalences of overweight (body mass index [BMI]
≥25) and obesity (BMI ≥30), using measured height and weight data.Design, Setting, and Participants Survey of 4115 adult men and women conducted in 1999 and 2000 as part
of the National Health and Nutrition Examination Survey (NHANES), a nationally
representative sample of the US population.Main Outcome Measure Age-adjusted prevalence of overweight, obesity, and extreme obesity
compared with prior surveys, and sex-, age-, and race/ethnicity–specific
estimates.Results The age-adjusted prevalence of obesity was 30.5% in 1999-2000 compared
with 22.9% in NHANES III (1988-1994; P<.001).
The prevalence of overweight also increased during this period from 55.9%
to 64.5% (P<.001). Extreme obesity (BMI ≥40)
also increased significantly in the population, from 2.9% to 4.7% (P = .002). Although not all changes were statistically significant,
increases occurred for both men and women in all age groups and for non-Hispanic
whites, non-Hispanic blacks, and Mexican Americans. Racial/ethnic groups did
not differ significantly in the prevalence of obesity or overweight for men.
Among women, obesity and overweight prevalences were highest among non-Hispanic
black women. More than half of non-Hispanic black women aged 40 years or older
were obese and more than 80% were overweight.Conclusions The increases in the prevalences of obesity and overweight previously
observed continued in 1999-2000. The potential health benefits from reduction
in overweight and obesity are of considerable public health importance.
Weight loss is a major concern for the US population. Surveys consistently show that most adults are trying to lose or maintain weight (1). Nevertheless, the prevalence of overweight and obesity has increased steadily over the past 30 years. Currently, 50% of all adult Americans are con- sidered overweight or obese (2,3). These numbers have serious public health implications. Excess weight is associ- ated with increased mortality (4) and morbidity (5). It is associated with cardiovascular disease, type 2 diabetes, hypertension, stroke, gallbladder disease, osteoarthritis, sleep apnea and respiratory problems, and some types of cancer (6,7).
Most people who are trying to lose weight are not using the recommended combination of reducing caloric intake and increasing physical activity (1). Although over 70% of persons reported using each of the following strategies at least once in 4 years, increased exercise (82.2%), decreased fat intake (78.7%), reduced food amount (78.2%,) and re- duced calories (73.2%), the duration of any one of these behaviors was brief. Even the most common behaviors were used only 20% of the time (8).
Obesity-related conditions are significantly improved with modest weight loss of 5% to 10%, even when many patients remain considerably overweight (6). The Institute of Medicine (9) defined successful long-term weight loss as a 5% reduction in initial body weight (IBW) that is main- tained for at least 1 year. Yet data suggest that such losses are not consistent with patients’ goals and expectations. Foster (10) reported that in obese women (mean body mass index [BMI] of 36.3 4.3) goal weights targeted, on average, a 32% reduction in IBW, implying expectations that are unrealistic for even the best available treatments. Interestingly, the most important factors that influenced the
Address correspondence to Dr. Janet King, U.S. Department of Agriculture, Agricultural Research Service, Western Human Nutrition Research Center, University of California, 1 Shield Avenue, Building Surge IV, Room 213, Davis, CA 95616. E-mail: jking@ whnrc.usda.gov
Copyright © 2001 NAASO
selection of goal weights were appearance and physical comfort rather than change in medical condition or weight suggested by a doctor or health care professional. Is it any wonder that overweight individuals are willing to try any new diet that promises quick, dramatic results more in line with their desired goals and expectations than with what good science supports?
The proliferation of diet books is nothing short of phe- nomenal. A search of books on Amazon.com using the key words “weight loss” revealed 1214 matches. Of the top 50 best-selling diet books, 58% were published in 1999 or 2000 and 88% were published since 1997. Many of the top 20 best sellers at Amazon.com promote some form of carbo- hydrate (CHO) restriction (e.g., Dr. Atkins’ New Diet Rev- olution, The Carbohydrate Addict’s Diet, Protein Power, Lauri’s Low-Carb Cookbook). This dietary advice is counter to that promulgated by governmental agencies (US Department of Agriculture [USDA]/Department of Health and Human Services, National Institutes of Health) and nongovernmental organizations (American Dietetic Associ- ation, American Heart Association, American Diabetes Association, American Cancer Society, and Shape Up America!).
What is really known about popular diets? Is the in- formation scientifically sound? Are popular diets effec- tive for weight loss and/or weight maintenance? What is the effect, if any, on composition of weight loss (fat vs. lean body mass), micronutrient (vitamin and mineral) status, metabolic parameters (e.g., blood glucose, insulin sensitivity, blood pressure, lipid levels, uric acid, and ketone bodies)? Do they affect hunger and appetite, psy- chological well-being, and reduction of risk for chronic disease (e.g., coronary heart disease, diabetes, and osteo- porosis)? What are the effects of these diets on insulin and leptin, long-term hormonal regulators of energy in- take and expenditure?
The objective of this article is to review the scientific literature on various types of popular diets based on their macronutrient composition in an attempt to answer these questions (see Appendix for diet summaries).
Some obese subjects repeatedly fail to lose weight even though they report restricting their caloric intake to less than 1200 kcal per day. We studied two explanations for this apparent resistance to diet--low total energy expenditure and underreporting of caloric intake--in 224 consecutive obese subjects presenting for treatment. Group 1 consisted of nine women and one man with a history of diet resistance in whom we evaluated total energy expenditure and its main thermogenic components and actual energy intake for 14 days by indirect calorimetry and analysis of body composition. Group 2, subgroups of which served as controls in the various evaluations, consisted of 67 women and 13 men with no history of diet resistance.
Total energy expenditure and resting metabolic rate in the subjects with diet resistance (group 1) were within 5 percent of the predicted values for body composition, and there was no significant difference between groups 1 and 2 in the thermic effects of food and exercise. Low energy expenditure was thus excluded as a mechanism of self-reported diet resistance. In contrast, the subjects in group 1 underreported their actual food intake by an average (+/- SD) of 47 +/- 16 percent and overreported their physical activity by 51 +/- 75 percent. Although the subjects in group 1 had no distinct psychopathologic characteristics, they perceived a genetic cause for their obesity, used thyroid medication at a high frequency, and described their eating behavior as relatively normal (all P < 0.05 as compared with group 2).
The failure of some obese subjects to lose weight while eating a diet they report as low in calories is due to an energy intake substantially higher than reported and an overestimation of physical activity, not to an abnormality in thermogenesis.
It is not known whether the decrease in the thermic effect of food (TEF) in obesity is a consequence of obesity or a factor contributing to the development of obesity. The resting energy expenditure (REE) of 24 obese, nondiabetic, postmenopausal women was 5481 +/- 110 kJ/24 h (1310 +/- 26.4 kcal/24 h). After weight loss (12.7 +/- 0.45 kg) the REE was significantly decreased (4858 +/- 94 kJ/24 h, or 1161 +/- 22.4 kcal/24 h) and equivalent to the REE of 4866 +/- 119 kJ/24 h (1163 +/- 28.5 kcal/24 h) in 24 never-obese, postmenopausal women. The TEF, expressed as a percentage of the calories ingested, was 8.2 +/- 0.50% for obese subjects, 8.7 +/- 0.57% for postobese subjects, and 9.8 +/- 0.54% for never-obese subjects. Compared with never-obese subjects, the TEF was significantly reduced in obese subjects (P = 0.043) and remained unchanged after weight loss (P = 0.341). These findings indicate that the lower TEF in the obese subjects is uncorrected by weight loss, and thus it is a contributor to obesity rather than a consequence of obesity.
The rates of energy expenditure and wholebody protein turnover were determined during a 9-h period in a group of seven men while they received hourly isocaloric meals of high-protein (HP) or high-carbohydrate (HC) content. Their responses to feeding were compared with those to a short period of fasting (15-24 h). The 9-h thermic response to the repeated feeding of HP meals was found to be greater than that to the HC meals (9.6 +/- 0.6% vs 5.7 +/- 0.4% of the energy intake, respectively, means +/- SEM, p less than 0.01). The rate of whole-body nitrogen turnover over 9 h increased from 17.6 +/- 2.2 g on the fasting day to 27.4 +/- 1.4 g during HC feeding (NS) and there was a further increase to 58.2 +/- 5.3 g resulting from HP feeding (p less than 0.001). By using theoretical estimates (based upon ATP requirements) of the metabolic cost of protein synthesis, 36 +/- 9% of the thermic response to HC feeding and 68 +/- 3% of the response to HP feeding could be accounted for by the increases in protein synthesis compared with the fasting state.
Total free living energy expenditure was compared in lean and obese women by the new doubly labelled water method and partitioned into basal metabolism and thermogenesis plus activity by whole body calorimetry. Average energy expenditure was significantly higher in the obese group (10.22 versus 7.99 MJ/day (2445 versus 1911 kcal/day); p less than 0.001) resulting from an increase in the energy cost of both basal metabolism and physical activity. Self recorded energy intakes were accurate in the lean subjects but underestimated expenditure by 3.5 MJ/day (837 kcal/day) in the obese group. Basal metabolic rate and energy expenditure on thermogenesis plus activity were identical in the two groups when corrected for differences in fat free mass and total body mass. In the obese women in this series there was no evidence that their obesity was caused by a metabolic or behavioural defect resulting in reduced energy expenditure.
A systemic reappraisal of the thermic effect of food was done in lean and obese males randomly fed mixed meals containing 0, 8, 16, 24, and 32 kcal/kg fat-free mass. Densitometric analysis was used to measure body composition. Preprandial and postprandial energy expenditures were measured by indirect calorimetry. The data show that the thermic effect of food was linearly correlated with caloric intake, and that the magnitude and duration of augmented postprandial thermogenesis increased linearly with caloric consumption. Postprandial energy expenditures over resting metabolic requirements were indistinguishable when comparing lean and obese men for a given caloric intake. Individuals, however, had distinct and consistent thermic responses to progressively greater caloric challenges. These unique thermic profiles to food ingestion were also independent of leanness or obesity. We conclude that the thermic effect of food increases linearly with caloric intake, and is independent of leanness and obesity.
There is a need to measure energy expenditure in man for a period of 24 h or even several days. The respiration chamber offers a unique opportunity to reach this goal. It allows the study of energy and nutrient balance; from the latter, acute changes in body composition can be obtained. The respiration chamber built in Lausanne is an air-tight room (5 m long, 2.5 m wide, and 2.5 m high) which forms an open circuit ventilated indirect calorimeter. The physical activity of the subject inside the chamber is continuously measured using a radar system based on the Doppler effect. Energy expenditure of obese and lean women was continuously measured over 24 h and diet-induced thermogenesis was assessed by using an approach which allows one to subtract the energy expended for physical activity from the total energy expenditure. Expressed in absolute terms, total energy expenditure was more elevated in the obese than in the lean controls. Basal metabolic rate was also higher in the obese than in the controls, but diet-induced thermogenesis was found to be blunted in the obese. In a second study, the effect of changing the carbohydrate/lipid content of the diet on fuel utilization was assessed in young healthy subjects with the respiration chamber. After a 7-day adaptation to a high-carbohydrate low-fat diet, the fuel mixture oxidized matched the change in nutrient intake. A last example of the use of the respiration chamber is the thermogenic response and changes in body composition due to a 7-day overfeeding of carbohydrate. Diet-induced thermogenesis was found to be 27%; on the last day of overfeeding, carbohydrate balance was reached by oxidation of 50% of the carbohydrate intake, the remaining 50% being converted into lipid.
The thermic effect of food (TEF), defined as the increase in metabolic rate after ingestion of a meal, has been studied extensively, but its role in body weight regulation is controversial. We analyzed 131 TEF tests from a wide range of subjects ingesting meals of varying sizes and compositions. Each test lasted 6 h. Of the total 6-h TEF, 60% of the total had been measured after 3 h. 78% after 4 h, and 91% after 5 h. We developed a three-parameter curve to fit the data, which reduced noise and gave additional information about the TEF. The area under this parametric curve was positively correlated with fat-free mass (FFM) and meal size (MS) and negatively correlated with meal size squared (MS2) with an R2 of 0.35. The usual area under a curve created by connecting the data points of a line was correlated with the same factors but with an R2 of 0.28. The peak of the parametric curve was positively correlated with FFM and MS and negatively correlated with MS2, percent body fat, and meal composition. The time at which the peak occurred correlated positively with MS and percent fat in the meal. Our analysis suggests that an inadequate measurement duration of the TEF could lead to errors. In general, we recommend that the TEF be measured for > or = 5 h.
Overweight and obesity are increasing dramatically in the United States and most likely contribute substantially to the burden of chronic health conditions.
To describe the relationship between weight status and prevalence of health conditions by severity of overweight and obesity in the US population.
Nationally representative cross-sectional survey using data from the Third National Health and Nutrition Examination Survey (NHANES III), which was conducted in 2 phases from 1988 to 1994.
A total of 16884 adults, 25 years and older, classified as overweight and obese (body mass index [BMI] > or =25 kg/m2) based on National Institutes of Health recommended guidelines.
Prevalence of type 2 diabetes mellitus, gallbladder disease, coronary heart disease, high blood cholesterol level, high blood pressure, or osteoarthritis.
Sixty-three percent of men and 55% of women had a body mass index of 25 kg/m2 or greater. A graded increase in the prevalence ratio (PR) was observed with increasing severity of overweight and obesity for all of the health outcomes except for coronary heart disease in men and high blood cholesterol level in both men and women. With normal-weight individuals as the reference, for individuals with BMIs of at least 40 kg/m2 and who were younger than 55 years, PRs were highest for type 2 diabetes for men (PR, 18.1; 95% confidence interval [CI], 6.7-46.8) and women (PR, 12.9; 95% CI, 5.7-28.1) and gallbladder disease for men (PR, 21.1; 95% CI, 4.1-84.2) and women (PR, 5.2; 95% CI, 2.9-8.9). Prevalence ratios generally were greater in younger than in older adults. The prevalence of having 2 or more health conditions increased with weight status category across all racial and ethnic subgroups.
Based on these results, more than half of all US adults are considered overweight or obese. The prevalence of obesity-related comorbidities emphasizes the need for concerted efforts to prevent and treat obesity rather than just its associated comorbidities.
The increasing prevalence of obesity is a major public health concern, since obesity is associated with several chronic diseases.
To monitor trends in state-specific data and to examine changes in the prevalence of obesity among adults.
Cross-sectional random-digit telephone survey (Behavioral Risk Factor Surveillance System) of noninstitutionalized adults aged 18 years or older conducted by the Centers for Disease Control and Prevention and state health departments from 1991 to 1998.
States that participated in the Behavioral Risk Factor Surveillance System.
Body mass index calculated from self-reported weight and height.
The prevalence of obesity (defined as a body mass index > or =30 kg/m2) increased from 12.0% in 1991 to 17.9% in 1998. A steady increase was observed in all states; in both sexes; across age groups, races, educational levels; and occurred regardless of smoking status. The greatest magnitude of increase was found in the following groups: 18- to 29-year-olds (7.1% to 12.1%), those with some college education (10.6% to 17.8%), and those of Hispanic ethnicity (11.6% to 20.8%). The magnitude of the increased prevalence varied by region (ranging from 31.9% for mid Atlantic to 67.2% for South Atlantic, the area with the greatest increases) and by state (ranging from 11.3% for Delaware to 101.8% for Georgia, the state with the greatest increases).
Obesity continues to increase rapidly in the United States. To alter this trend, strategies and programs for weight maintenance as well as weight reduction must become a higher public health priority.
The prevalence of obesity and overweight increased in the United States between 1978 and 1991. More recent reports have suggested continued increases but are based on self-reported data.
To examine trends and prevalences of overweight (body mass index [BMI] > or = 25) and obesity (BMI > or = 30), using measured height and weight data.
Survey of 4115 adult men and women conducted in 1999 and 2000 as part of the National Health and Nutrition Examination Survey (NHANES), a nationally representative sample of the US population.
Age-adjusted prevalence of overweight, obesity, and extreme obesity compared with prior surveys, and sex-, age-, and race/ethnicity-specific estimates.
The age-adjusted prevalence of obesity was 30.5% in 1999-2000 compared with 22.9% in NHANES III (1988-1994; P<.001). The prevalence of overweight also increased during this period from 55.9% to 64.5% (P<.001). Extreme obesity (BMI > or = 40) also increased significantly in the population, from 2.9% to 4.7% (P =.002). Although not all changes were statistically significant, increases occurred for both men and women in all age groups and for non-Hispanic whites, non-Hispanic blacks, and Mexican Americans. Racial/ethnic groups did not differ significantly in the prevalence of obesity or overweight for men. Among women, obesity and overweight prevalences were highest among non-Hispanic black women. More than half of non-Hispanic black women aged 40 years or older were obese and more than 80% were overweight.
The increases in the prevalences of obesity and overweight previously observed continued in 1999-2000. The potential health benefits from reduction in overweight and obesity are of considerable public health importance.
Despite the popularity of the low-carbohydrate, high-protein, high-fat (Atkins) diet, no randomized, controlled trials have evaluated its efficacy.
We conducted a one-year, multicenter, controlled trial involving 63 obese men and women who were randomly assigned to either a low-carbohydrate, high-protein, high-fat diet or a low-calorie, high-carbohydrate, low-fat (conventional) diet. Professional contact was minimal to replicate the approach used by most dieters.
Subjects on the low-carbohydrate diet had lost more weight than subjects on the conventional diet at 3 months (mean [+/-SD], -6.8+/-5.0 vs. -2.7+/-3.7 percent of body weight; P=0.001) and 6 months (-7.0+/-6.5 vs. -3.2+/-5.6 percent of body weight, P=0.02), but the difference at 12 months was not significant (-4.4+/-6.7 vs. -2.5+/-6.3 percent of body weight, P=0.26). After three months, no significant differences were found between the groups in total or low-density lipoprotein cholesterol concentrations. The increase in high-density lipoprotein cholesterol concentrations and the decrease in triglyceride concentrations were greater among subjects on the low-carbohydrate diet than among those on the conventional diet throughout most of the study. Both diets significantly decreased diastolic blood pressure and the insulin response to an oral glucose load.
The low-carbohydrate diet produced a greater weight loss (absolute difference, approximately 4 percent) than did the conventional diet for the first six months, but the differences were not significant at one year. The low-carbohydrate diet was associated with a greater improvement in some risk factors for coronary heart disease. Adherence was poor and attrition was high in both groups. Longer and larger studies are required to determine the long-term safety and efficacy of low-carbohydrate, high-protein, high-fat diets.
In vivo lipogenesis and thermogenesis were studied for 24 h after ingestion of 500 g of carbohydrate (CHO) in subjects who had consumed either a high-fat, a mixed, or a high-CHO diet during the 3-6 days preceding the test. CHO oxidation and conversion to fat was significantly less in the high-fat diet group (222 ± 5 g) than in the mixed (300 ± 13 g) or high-CHO diet (331 ± 7 g) groups, resulting in a greater glycogen storage in the high-fat (278 ± 6 g) than in the other two groups (197 ± 11 and 170 ± 2 g). Net lipogenesis occurred sooner and lasted longer in the high-CHO group, amounting to 0.8 ± 0.5, 3.4 ± 0.6, and 9 ± 1 g of lipid synthesized in the high-fat, mixed, and high-CHO groups, respectively. The thermic effect of the CHO load was 5.2 ± 0.5% on the high-fat, 6.5 ± 0.4% on the mixed diet, and 8.6 ± 0.4% on the high-CHO diet. Significant relationships were demonstrated between the postabsorptive nonprotein respiratory quotient and net lipogenesis after the CHO lead (r = 0.82) and between net lipogenesis and in the increase in energy expenditure (r = 0.71). It is concluded that the antecedent diet influences the amount of net lipogenesis and the magnitude of thermogenesis after a large CHO test meal. However, lipogenesis remains too limited even after such large CHO intakes to cause an increase in the body's fat content.
Context:
The increasing prevalence of obesity is a major public health concern, since obesity is associated with several chronic diseases.
Objective:
To monitor trends in state-specific data and to examine changes in the prevalence of obesity among adults.
Design:
Cross-sectional random-digit telephone survey (Behavioral Risk Factor Surveillance System) of noninstitutionalized adults aged 18 years or older conducted by the Centers for Disease Control and Prevention and state health departments from 1991 to 1998.
Setting:
States that participated in the Behavioral Risk Factor Surveillance System.
Main outcome measures:
Body mass index calculated from self-reported weight and height.
Results:
The prevalence of obesity (defined as a body mass index > or =30 kg/m2) increased from 12.0% in 1991 to 17.9% in 1998. A steady increase was observed in all states; in both sexes; across age groups, races, educational levels; and occurred regardless of smoking status. The greatest magnitude of increase was found in the following groups: 18- to 29-year-olds (7.1% to 12.1%), those with some college education (10.6% to 17.8%), and those of Hispanic ethnicity (11.6% to 20.8%). The magnitude of the increased prevalence varied by region (ranging from 31.9% for mid Atlantic to 67.2% for South Atlantic, the area with the greatest increases) and by state (ranging from 11.3% for Delaware to 101.8% for Georgia, the state with the greatest increases).
Conclusions:
Obesity continues to increase rapidly in the United States. To alter this trend, strategies and programs for weight maintenance as well as weight reduction must become a higher public health priority.
This is a three-part study that examined the accuracy of five brands of electronic pedometers (Freestyle Pacer, Eddie Bauer, L.L. Bean, Yamax, and Accusplit) under a variety of different conditions. In Part I, 20 subjects walked a 4.88-km sidewalk course while wearing two devices of the same brand (on the left and right side of the body) for each of five different trials. There were significant differences among pedometers (P < 0.05), with the Yamax, Pacer, and Accusplit approximating the actual distance more closely than the other models. The Yamax pedometers showed close agreement, but the left and right Pacer pedometers differed significantly (P = 0.0003) and the Accusplit displayed a similar trend (P = 0.0657). In Part II, the effects of walking surface on pedometer accuracy were examined. Ten of the original subjects completed an additional five trials around a 400-m rubberized outdoor track. The devices showed similar values for sidewalk and track surfaces. In Part III, the effects of walking speed on pedometer accuracy were examined. Ten different subjects walked on a treadmill at various speeds (54, 67, 80, 94, and 107 m.min-1). Pedometers that displayed both distance and number of steps were examined. The Yamax was more accurate than the Pacer and Eddie Bauer at slow-to-moderate speeds (P < 0.05), though no significant differences were seen at the fastest speed. While there are variations among brands in terms of accuracy, electronic pedometers may prove useful in recording walking activities in free-living populations.
The aim of this study was to evaluate the use of the pedometer in epidemiologic research on physical activity. Within the framework of a health examination survey in 1988–1989, physical activity was assessed in a representative population sample of 493 men and women aged 25–74 years who were residents of Switzerland. They wore a pedometer for 1 week at work and during leisure time, and the results, converted into steps per day, were compared with answers to a questionnaire. The average number of steps per day decreased from 11,900 to 6,700 and from 9,300 to 7,300 for men and women, respectively, in the youngest to the oldest age groups. For men, categorized according to type of physical activity at work, there was a highly significant difference in the number of steps (p< 0.001), whereas in women the results were associated with leisure-time physical activity (p = 0.003). For both sexes, practicing sports more than once a week was associated with an important increase in steps per day. Analyzing the number of steps according to the day of the week and occupational category produced an unexpected result: Men with a physically active job engaged in more leisure-time physical activity on the weekend. The pedometer proved to be useful in assessing physical activity in a large, free-living population.
Twenty-four hour energy expenditure (24EE) can be measured in a respiratory chamber. 24EE is comprised of the basal metabolic rate, the thermic effect of food, and the energy cost of physical activity. The major determinant of 24EE, fat-free mass, accounts for approximately 80% of the variance observed between individuals. Genetic factors seem to be the cause of the familial aggregation of 24EE in man. The variability of 24EE for a given body size and composition is of importance because a low metabolic rate is a major risk factor for weight gain in man. There is increasing evidence that obesity, often an inherited disorder, cannot always be attributed to gluttony and sloth. Similar to the need to treat essential hypertension, there is a need to treat a disorder perhaps best called essential obesity.
We measured body composition, basal metabolic rate (BMR), and total energy expenditure in 28 nonobese and 35 obese adolescents aged 12-18 y using indirect calorimetry and the doubly labeled water method. BMR was highly correlated with fat-free mass in both the nonobese and obese groups (r = 0.77 and 0.84, respectively). BMR adjusted for fat-free mass was significantly greater in males than females and in the obese subjects. Total energy expenditure was significantly greater in the obese than nonobese cohort but ratios of total energy expenditure/BMR were not significantly different in the two groups (1.79 +/- 0.2 versus 1.68 +/- 0.19, nonobese and obese males and 1.69 +/- 0.28 versus 1.74 +/- 0.19 nonobese and obese females, respectively). These data indicate that BMR and total energy expenditure are not reduced in the already obese adolescent. Therefore, reduced energy expenditure cannot be responsible for the maintenance of obesity in adolescents.
It is the aim of this symposium to review our current understanding of many of the factors that affect the regulation of energy balance in humans and to discuss some of the newer methods available for measuring energy expenditure over prolonged periods of time. The review is, by necessity, highly selective and many important topics in this rapidly expanding field of investigation have been omitted. The purpose of this introductory overview is merely to set the stage for the papers which follow.
In vivo lipogenesis and thermogenesis were studied for 24 h after ingestion of 500 g of carbohydrate (CHO) in subjects who had consumed either a high-fat, a mixed, or a high-CHO diet during the 3-6 days preceding the test. CHO oxidation and conversion to fat was significantly less in the high-fat diet group (222 +/- 5 g) than in the mixed (300 +/- 13 g) or high-CHO diet (331 +/- 7 g) groups, resulting in a greater glycogen storage in the high-fat (278 +/- 6 g) than in the other two groups (197 +/- 11 and 170 +/- 2 g). Net lipogenesis occurred sooner and lasted longer in the high-CHO group, amounting to 0.8 +/- 0.5, 3.4 +/- 0.6, and 9 +/- 1 g of lipid synthesized in the high-fat, mixed, and high-CHO groups, respectively. The thermic effect of the CHO load was 5.2 +/- 0.5% on the high-fat, 6.5 +/- 0.4% on the mixed diet, and 8.6 +/- 0.4% on the high-CHO diet. Significant relationships were demonstrated between the postabsorptive nonprotein respiratory quotient and net lipogenesis after the CHO load (r = 0.82) and between net lipogenesis and the increase in energy expenditure (r = 0.71). It is concluded that the antecedent diet influences the amount of net lipogenesis and the magnitude of thermogenesis after a large CHO test meal. However, lipogenesis remains too limited even after such large CHO intakes to cause an increase in the body's fat content.
The aim of this study was to evaluate the use of the pedometer in epidemiologic research on physical activity. Within the framework of a health examination survey in 1988-1989, physical activity was assessed in a representative population sample of 493 men and women aged 25-74 years who were residents of Switzerland. They wore a pedometer for 1 week at work and during leisure time, and the results, converted into steps per day, were compared with answers to a questionnaire. The average number of steps per day decreased from 11,900 to 6,700 and from 9,300 to 7,300 for men and women, respectively, in the youngest to the oldest age groups. For men, categorized according to type of physical activity at work, there was a highly significant difference in the number of steps (p < 0.001), whereas in women the results were associated with leisure-time physical activity (p = 0.003). For both sexes, practicing sports more than once a week was associated with an important increase in steps per day. Analyzing the number of steps according to the day of the week and occupational category produced an unexpected result: Men with a physically active job engaged in more leisure-time physical activity on the weekend. The pedometer proved to be useful in assessing physical activity in a large, free-living population.
This prospective study was designed to identify abnormalities of energy expenditure and fuel utilization which distinguish post-obese women from never-obese controls. 24 moderately obese, postmenopausal, nondiabetic women with a familial predisposition to obesity underwent assessments of body composition, fasting and postprandial energy expenditure, and fuel utilization in the obese state and after weight loss (mean 12.9 kg) to a post-obese, normal-weight state. The post-obese women were compared with 24 never-obese women of comparable age and body composition. Four years later, without intervention, body weight was reassessed in both groups. Results indicated that all parameters measured in the post-obese women were similar to the never-obese controls: mean resting energy expenditure, thermic effect of food, and fasting and postprandial substrate oxidation and insulin-glucose patterns. Four years later, post-obese women regained a mean of 10.9 kg while control subjects remained lean (mean gain 1.7 kg) (P < 0.001 between groups). Neither energy expenditure nor fuel oxidation correlated with 4-yr weight changes, whereas self-reported physical inactivity was associated with greater weight regain. The data suggest that weight gain in obesity-prone women may be due to maladaptive responses to the environment, such as physical inactivity or excess energy intake, rather than to reduced energy requirements.
Measurements of total energy expenditure (TEE) by the doubly labeled water method were compiled from 22 studies to identify the range of variation and significant determinants of energy requirements in healthy adults. The 126 male and 173 female subjects (aged 18-78 y) were separated into four groups: athletes, Pima Indians, people in developing countries, and others. The groups differed significantly (P < 0.001) with respect to TEE, TEE/BMR, TEE-BMR divided by weight, and TEE-BMR. Stepwise multiple regression demonstrated that fat-free mass (FFM) and age are significant variables that can explain 65% of the variation in TEE. These data demonstrate that total daily energy expenditure varies dramatically among healthy, free-living adults. The relationship between body fatness and nonbasal energy expenditure was negative at high energy outputs but considerable variation in body fatness was present among sedentary individuals, suggesting that a low rate of nonbasal energy expenditure is a permissive factor for obesity.
This paper reviews evidence that the macro-nutrient composition of the diet and the maintenance of energy balance are correlated. Intervention studies show that subjects lose weight on low-fat diets and gain weight on high-fat diets. Descriptive studies show that overweight subjects eat relatively more fat but have the same total energy intake as nonoverweight subjects. The body has a limited ability to oxidize fat compared with its ability to oxidize carbohydrate and protein. The conclusion is that becoming overweight can be prevented by reducing the fat content of the diet. Studies on nutrient utilization show a ready increase in carbohydrate oxidation whereas fat oxidation does not change after meals enriched with, respectively, carbohydrate or fat. However, in the long term, the respiratory quotient (RQ) is closer to the food quotient (FQ) for subjects eating high-fat diets than it is for subjects eating high-carbohydrate diets. For high-carbohydrate diets, the RQ is lower than is the FQ, indicating that subjects must mobilize body fat. This is supported by data on body weight loss in subjects changing from a standard maintenance diet to a low-fat diet, even while energy intake was increased with nearly 20%. Direct evidence for a higher energy expenditure for low-fat diets is not yet available.
This is a three-part study that examined the accuracy of five brands of electronic pedometers (Freestyle Pacer, Eddie Bauer, L.L. Bean, Yamax, and Accusplit) under a variety of different conditions. In Part I, 20 subjects walked a 4.88-km sidewalk course while wearing two devices of the same brand (on the left and right side of the body) for each of five different trials. There were significant differences among pedometers (P < 0.05), with the Yamax, Pacer, and Accusplit approximating the actual distance more closely than the other models. The Yamax pedometers showed close agreement, but the left and right Pacer pedometers differed significantly (P = 0.0003) and the Accusplit displayed a similar trend (P = 0.0657). In Part II, the effects of walking surface on pedometer accuracy were examined. Ten of the original subjects completed an additional five trials around a 400-m rubberized outdoor track. The devices showed similar values for sidewalk and track surfaces. In Part III, the effects of walking speed on pedometer accuracy were examined. Ten different subjects walked on a treadmill at various speeds (54, 67, 80, 94, and 107 m.min-1). Pedometers that displayed both distance and number of steps were examined. The Yamax was more accurate than the Pacer and Eddie Bauer at slow-to-moderate speeds (P < 0.05), though no significant differences were seen at the fastest speed. While there are variations among brands in terms of accuracy, electronic pedometers may prove useful in recording walking activities in free-living populations.
To evaluate energy expenditure after three isoenergetic meals of different nutrient composition and to establish the relationship between the thermic effect of food (TEF), subsequent energy intake from a test meal and satiety sensations related to consumption.
The study employed a repeated measures design. Ten subjects received, in a randomized order, three meals of 2331+/-36 kJ (557+/-9 kcal). About 68% of energy from protein in the high protein meal (HP), 69% from carbohydrate in the high carbohydrate meal (HC) and 70% from fat in the high fat meal (HF).
The experiments were performed at the University of Milan. Subjects: Ten normal body-weight healthy women.
Energy expenditure was measured by indirect calorimetric measurements, using an open-circuit ventilated-hood system; intake was assessed 7h later by weighing the food consumed from a test meal and satiety sensations were rated by means of a satiety rating questionnaire.
TEF was 261+/-59, 92+/-67 and 97+/-71 kJ over 7 h after the HP, HC and HF meals, respectively. The HP meal was the most thermogenic (P < 0.001) and it determined the highest sensation of fullness (P=0.002). There were no differences in the sensations and thermic effect between fat and carbohydrate meals. A significant relationship linked TEF to fullness sensation (r=0.41, P=0.025). Energy intake from the test meal was comparable after HP, HC and HF meals.
Our results suggest that TEF contributes to the satiating power of foods.
One hundred thirty subjects were studied to investigate relationships between the body composition and fat distribution as evaluated by computed tomography and the resting metabolic rate (RMR) as evaluated by indirect calorimetry: 82 premenopausal women (age, 18 to 52 years; body mass index [BMI], 27 to 52 kg/m2), 27 postmenopausal women (46 to 71 years; 28 to 49 kg/m2), and 21 men (18 to 70 years; 31 to 43 kg/m2). The thermic effect of food (TEF) was evaluated in all men and in 2 subgroups of 55 and 19 women. The best-fitting equations for predicting RMR, obtained by multiple regression, included the following as covariates: fat-free mass and both subcutaneous and visceral adipose tissue in premenopausal women (R2 = .55, P = .0001), fat-free mass and visceral adipose tissue in postmenopausal women (R2 = .58, P = .001), and age, with minus sign, and visceral adipose tissue in men (R2 = .44, P = .0051). Fasting insulin and fat-free mass, with minus sign, and both visceral and subcutaneous adipose tissue were the predictors of the TEF (R2 = .25, P = .0055) in premenopausal women. This study demonstrates that visceral fat distribution is important in determining the RMR in postmenopausal women and men. In premenopausal women, total adipose tissue is a main determinant of both the RMR and TEF This last effect could be counterbalanced by insulin resistance.
The Digi-Walker step counter is a promising and cost-effective tool to measure physical activity under free-living conditions. Two specific studies were conducted to evaluate the number of steps required to meet current physical activity guidelines.
Thirty-one adults (17 men, 14 women) served as participants. In study 1, we determined the number of steps to complete a mile under two different conditions and three paces. In study 2, we conducted a field trial to examine the relationship between daily step counts and other indices of physical activity. Participants in this study wore a Digi-Walker for 2 consecutive weeks and completed the 7-d physical activity recall (PAR) after each week.
In study 1, there were no differences in step counts by site, but steps were inversely related to pace, with values ranging from 1330 to 1996. Individual step counts at a specific pace were negatively correlated with height, weight, leg length, and stride length and were positively correlated with body fatness. In study 2, participants had average daily step counts of 11,603 when structured vigorous activity was included and 8265 when only light and moderate activity were measured. Modest correlations were found between step counts and estimated energy expenditure. Similar correlations were observed when step counts were related to minutes of activity per day and minutes of sitting per day.
Pedometers provide a useful indicator of daily step counts but variability in activity patterns make it difficult to establish step count guidelines that correspond with other public health guidelines.
Untested alternative weight loss diets, such as very low carbohydrate diets, have unsubstantiated efficacy and the potential to adversely affect cardiovascular risk factors. Therefore, we designed a randomized, controlled trial to determine the effects of a very low carbohydrate diet on body composition and cardiovascular risk factors. Subjects were randomized to 6 months of either an ad libitum very low carbohydrate diet or a calorie-restricted diet with 30% of the calories as fat. Anthropometric and metabolic measures were assessed at baseline, 3 months, and 6 months. Fifty-three healthy, obese female volunteers (mean body mass index, 33.6 +/- 0.3 kg/m(2)) were randomized; 42 (79%) completed the trial. Women on both diets reduced calorie consumption by comparable amounts at 3 and 6 months. The very low carbohydrate diet group lost more weight (8.5 +/- 1.0 vs. 3.9 +/- 1.0 kg; P < 0.001) and more body fat (4.8 +/- 0.67 vs. 2.0 +/- 0.75 kg; P < 0.01) than the low fat diet group. Mean levels of blood pressure, lipids, fasting glucose, and insulin were within normal ranges in both groups at baseline. Although all of these parameters improved over the course of the study, there were no differences observed between the two diet groups at 3 or 6 months. beta- Hydroxybutyrate increased significantly in the very low carbohydrate group at 3 months (P = 0.001). Based on these data, a very low carbohydrate diet is more effective than a low fat diet for short-term weight loss and, over 6 months, is not associated with deleterious effects on important cardiovascular risk factors in healthy women.
The effects of a carbohydrate-restricted diet on weight loss and risk factors for atherosclerosis have been incompletely assessed.
We randomly assigned 132 severely obese subjects (including 77 blacks and 23 women) with a mean body-mass index of 43 and a high prevalence of diabetes (39 percent) or the metabolic syndrome (43 percent) to a carbohydrate-restricted (low-carbohydrate) diet or a calorie- and fat-restricted (low-fat) diet.
Seventy-nine subjects completed the six-month study. An analysis including all subjects, with the last observation carried forward for those who dropped out, showed that subjects on the low-carbohydrate diet lost more weight than those on the low-fat diet (mean [+/-SD], -5.8+/-8.6 kg vs. -1.9+/-4.2 kg; P=0.002) and had greater decreases in triglyceride levels (mean, -20+/-43 percent vs. -4+/-31 percent; P=0.001), irrespective of the use or nonuse of hypoglycemic or lipid-lowering medications. Insulin sensitivity, measured only in subjects without diabetes, also improved more among subjects on the low-carbohydrate diet (6+/-9 percent vs. -3+/-8 percent, P=0.01). The amount of weight lost (P<0.001) and assignment to the low-carbohydrate diet (P=0.01) were independent predictors of improvement in triglyceride levels and insulin sensitivity.
Severely obese subjects with a high prevalence of diabetes or the metabolic syndrome lost more weight during six months on a carbohydrate-restricted diet than on a calorie- and fat-restricted diet, with a relative improvement in insulin sensitivity and triglyceride levels, even after adjustment for the amount of weight lost. This finding should be interpreted with caution, given the small magnitude of overall and between-group differences in weight loss in these markedly obese subjects and the short duration of the study. Future studies evaluating long-term cardiovascular outcomes are needed before a carbohydrate-restricted diet can be endorsed.
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- Triglycerides
Triglycerides (mg/dl)
128.85 (13.44)
78.80 (4.82)
80.75 (6.11)
145.63 (19.95)
129.45 (10.30)
130.65 (13.41)
LDL (mg/dl)
134.85 (8.26)
130.10 (7.16)
131.90 (9.93)
125.28 (5.95)
111.15 (7.35)
116.60 (8.08)
HDL (mg/dl)
44.40 (2.11)
48.10 a (2.71)
51.65 a (2.55)
44.21 (1.69)
43.50 (2.02)
46.20 (2.08)