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Preservation of Fat-Free Mass After Two Distinct Weight Loss Diets with and without Progressive Resistance Exercise
Abstract
Preserving fat-free mass (FFM) during weight loss is important in older adults. The purpose was to examine a low-fat diet (LFD) versus a carbohydrate-restricted diet (CRD) with and without progressive resistance exercise (PRE) on preservation of FFM in older men with metabolic syndrome.
A total of 42 men (59±7 years) were matched [body mass index (BMI)] and randomized to LFD, LFD&PRE, CRD, and CRD&PRE. PRE groups performed supervised strength training three times per week. Body weight, composition, metabolic syndrome criteria, and strength were measured at baseline and week 12. A 3-day diet record was kept at baseline and at weeks 1, 6, and 12.
Attrition (24%) was similar between groups. Depicted as % carbohydrate:fat:protein, the intervention diet was: LFD=55:24:18, LFD&PRE=57:20:20, CRD=16:54:28, and CRD&PRE=12:56:31. Weight (lb) decreased similarly in all groups (LFD, -18.0±7.4; LFD&PRE, -19.8±12.8; CRD, -20.2±8.0; CRD&PRE, -22.7±6.0; P<0.001), and number of participants with metabolic syndrome decreased in all groups (-3, -6, -3, -4, respectively). Percent of weight loss from appendicular FFM was 27.5%, 15.9%, 15.7%, and 17.3% respectively. A trend was found when comparing LFD and LFD&PRE (P=0.068), and when comparing LFD&CRD (P=0.072). Triglycerides improved more for the LFD&PRE, CRD, and CRD&PRE groups compared to the LFD group (P<0.05). Improvements in high-density lipoprotein-cholesterol were better in the CRD&PRE group (4.1±5.1 mg/dL) versus the LFD group (-5.0±5.9 mg/dL; P<0.01).
LFD&PRE, CRD, and CRD&PRE preserve FFM similarly. PRE is an important component of a LFD during weight loss in this population.
... Un total de 285 personas fueron incluidas en los diversos estudios analizados (Tabla I). Así, cuatro de los estudios utilizaron como muestras objeto de estudio a hombres y mujeres (7-9,13), un estudio incluía solo hombres (12), dos solo mujeres (10,11). ...
... Del total de estudios analizados se recogieron solo aquellos que analizaron pérdida de masa grasa y el efecto de la dieta baja en carbohidratos con o sin práctica de ejercicio. Un total de cuatro estudios (7,(11)(12)(13) de los seleccionados para la revisión sistemática fueron incluidos en el metaanálisis (Fig. 1). El metaanálisis incluyó aquellos artículos que incluían datos de media y desviación estándar antes y después de la intervención de dieta baja en carbohidratos y ejercicio. ...
... Analizando los artículos incluidos en el metaanálisis, se encontraron tamaños del efecto grandes (7), medios (11) y pequeños (12,13) pero siempre indicando una mayor reducción en el grupo experimental. ...
Introduction:
practice of physical activity and the ketogenic diet monitoring can have a double effect in helping in processes of weight loss and improvement of body composition and lipid profile.
Objective:
the objective of this review was to investigate the work done with obese patients who undertook a ketogenic diet and a physical exercise program, as well as to calculate the overall effect size in terms of improvements in fat mass, through a meta-analysis.
Methods:
the selection of studies was based on the following criteria: experimental studies; a) experimental studies (randomized controlled designs) and quasi-experimental (e.g. pre-test/post-test); b) studies with low-carbohydrate diet (< 30%) or very low in carbohydrates (5-10%) (< 50 g Ch) and/or high in fats (> 35%); c) studies were admitted exclusively with subjects that facility overweight or obesity (BMI > 25; and d) with measurements of body composition and/or Lipid profile at the beginning and end of the intervention.
Results:
for the methodological review, 7 articles and 3 reviews were analyzed. All studies, whether by establishing aerobic or strength training and show significant weight loss in all outcomes.
Conclusions:
comparing different types of exercise, we could say that interventions based on endurance exercise reported a decrease in muscle mass, however there was a maintenance, and even an increase, in studies with resistance exercises. Meta-analysis showed significant results at the global level with a medium heterogeneity, therefore, there will be greater reduction of fat mass in groups that realize diets with low carbohydrates and exercise that in those who do not undertake this type of diet, and those only perform exercise.
... Resistance training can increase muscle mass and help mitigate loss of fat-free mass during weight loss (Ballor et al., 1988;Delmonico & Lofgren, 2010;Stiegler & Cunliffe, 2006). Only two studies were located that investigated whether combining resistance training with a ketogenic diet provides superior changes in body composition relative to other diets in combination with resistance training (Jabekk et al., 2010;Wood et al., 2012). These studies are summarized in Table 2. ...
... As detailed in Table 2, these studies were markedly different on a number of factors, including subject age and gender, frequency of strength training, exercise selection, sets and repetitions performed, and method of body composition assessment. Jabekk et al. (2010) reported no change in fat-free mass in subjects following a resistance training program in combination with a ketogenic diet, and Wood et al. (2012) reported a decrease. However, the results from Wood et al. (2012) indicated that, without exercise, a ketogenic diet led to less fat-free mass loss than a low-fat diet and similar losses as compared to a low-fat diet plus resistance training. ...
... Jabekk et al. (2010) reported no change in fat-free mass in subjects following a resistance training program in combination with a ketogenic diet, and Wood et al. (2012) reported a decrease. However, the results from Wood et al. (2012) indicated that, without exercise, a ketogenic diet led to less fat-free mass loss than a low-fat diet and similar losses as compared to a low-fat diet plus resistance training. The results of Jabekk et al. (2010) could also be viewed as positive in regard to the efficacy of a ketogenic diet and resistance training because fat-free mass was not lost, whereas a relatively large amount of fat mass was lost (M ± SD = −5.6 ± 2.6 kg). ...
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 mean age of the participants varied between 21 and 72 years with studies ranging from a sample size of 14 to 241 participants. exercise, two included a combination of aerobic 12,19 exercise with circuit training, whereas only one included progressive resistance exercise as the kind of 6 physical activity. The kind of diet regimen varied from 6,17,18 17-19 6,7,10,17 low fat, healthy no sugar, to caloric restricted. ...
... As the trials proceeded, besides the experimental intervention, [6][7][8][9][10][11][12][13][14][15][16][17][18][19] all the groups were treated equally in all the studies. All the 14 studies clearly specified their primary as well as secondary outcomes, with 10 studies that included at least one of the metabolic risk factors as the primary [8][9][10][11][12][13]15,[17][18][19] outcome. ...
... An overall reduction in both SBP and DBP was observed in all the seven trials with two trials demonstrating a shift 7,10 from high to normal range BP post-intervention. The statistical significance was set at p < 0.05 with only four 6,[17][18][19] of the seven trials reaching the same. ...
Background: Dramatic economic growth in the past few decades has led to westernization of diets, increasingly sedentary lifestyle and a decrease in physical activity. As a result metabolic syndrome has emerged as a major global public health issue. The purpose of this systematic review is to examine the effect of physical activity on various metabolic syndrome outcomes which includes: blood pressure, triglyceride and HDL-C level, waist circumference, fasting blood glucose. This could help strategize future major researches and formulation of policies as basis for recommendation and prescribing physical activity interventions in both developed and developing countries.
... To date, 10 controlled trials have investigated the effects of a ketogenic diet on strength training performance (Table 2) [22,71,[86][87][88][89][90][91][92][93]. Of these, only one exclusively involved women, while four included both men and women; participants were either untrained before the intervention (1 trial), recreationally active (6 trials), or involved in a competitive sport (3 trials); the exercise intervention was to maintain usual exercise habits (4 trials) or follow a prescribed routine (6 trials); and dietary monitoring was either via food logs (9 trials) or not described (1 trial). ...
... To date, 19 controlled trials have investigated the effects of a ketogenic diet on body composition (Table 3) [22,35,36,[41][42][43]46,71,[86][87][88][89][90][91][92][93][112][113][114]. Of these, only two involved exclusively females, while 11 involved exclusively males; participants were either untrained before the intervention (2 trials), recreationally active (14 trials), or involved in a competitive sport (3 trials); the exercise intervention was to maintain usual exercise habits (9 trials) or follow a prescribed routine (10 trials); and dietary monitoring was either via food logs (17 trials) or not described (2 trials). ...
ABSTRACT
Position statement: The International Society of Sports Nutrition
(ISSN) provides an objective and critical review of the use of
a ketogenic diet in healthy exercising adults, with a focus on
exercise performance and body composition. However, this review
does not address the use of exogenous ketone supplements. The
following points summarize the position of the ISSN:
1. A ketogenic diet induces a state of nutritional ketosis, which is
generally defined as serum ketone levels above 0.5 mM. While
many factors can impact what amount of daily carbohydrate intake will result in these levels, a broad guideline is a daily dietary
carbohydrate intake of less than 50 grams per day.
2. Nutritional ketosis achieved through carbohydrate restriction
and a high dietary fat intake is not intrinsically harmful and should
not be confused with ketoacidosis, a life-threatening condition
most commonly seen in clinical populations and metabolic
dysregulation.
3. A ketogenic diet has largely neutral or detrimental effects on
athletic performance compared to a diet higher in carbohydrates
and lower in fat, despite achieving significantly elevated levels of fat oxidation during exercise (~1.5 g/min).
4. The endurance effects of a ketogenic diet may be influenced
by both training status and duration of the dietary intervention, but further research is necessary to elucidate these possibilities. All studies involving elite athletes showed a performance decrement from a ketogenic diet, all lasting six weeks or less. Of the two studies lasting more than six weeks, only one reported a statistically significant benefit of a ketogenic diet.
5. A ketogenic diet tends to have similar effects on maximal
strength or strength gains from a resistance training program compared to a diet higher in carbohydrates. However, a minority of studies show superior effects of non-ketogenic comparators.
6. When compared to a diet higher in carbohydrates and lower in
fat, a ketogenic diet may cause greater losses in body weight, fat
mass, and fat-free mass, but may also heighten losses of lean tissue. However, this is likely due to differences in calorie and protein
intake, as well as shifts in fluid balance.
7. There is insufficient evidence to determine if a ketogenic diet
affects males and females differently. However, there is a strong
mechanistic basis for sex differences to exist in response to a ketogenic diet.
... Brinkworth et al. (2007) reported that 10 weeks of CRD unaccompanied by RT did not impair isometric strength in overweight women. Another study (Wood et al., 2012) compared the effects of a low-fat diet with a CRD combined with progressive RT on preservation of FFM in older men and concluded that both types of diet similarly preserve FFM. However, this study did not measure strength performance changes during the 12-week program. ...
... In the present study, body mass, body fat, and waist girth were significantly reduced, whereas fat-free mass was maintained in both CRD and CONV diet groups. Similar to findings by Jabekk et al. (2010) and Wood et al. (2012), which followed overweight women and men submitted to 10 weeks and 12 weeks of RT combined with CRD, respectively. ...
Method:
At baseline and week 8, the participants underwent body composition assessment by anthropometry, measurement of muscle thickness by ultrasound, and three strength tests using isotonic equipment. Both groups had similar reductions in body mass and fat mass as well as maintenance of fat-free mass. Muscle strength increased 14 ± 6% in the CRD group (p = 0.005) and 19 ± 9% in the CONV group (p = 0.028), with no significant differences between the groups. No significant differences were detected in muscle thicknesses within or between the groups. In conclusion, hypoenergetic diets combined with RT led to significant increases in muscle strength and were capable of maintaining muscle thicknesses in the upper and lower limbs of overweight and obese participants, regardless of the carbohydrate content of the diets.
... Three studies did not provide BMI data (24,25,44 (52) and one included participants with non-alcoholic fatty liver disease (51). Ad libitum intakes were measured by weighed intakes of foods from a menu (13,(18)(19)(20)(21)28,33,35,38,43,48,49,51) or supplied through a shop set up for the study (27,34,45,50) or diet regime (26) or through analysis of food diary information (22)(23)(24)(25)31,32,34,36,39,41,44,46,47,50,(52)(53)(54). Each study prescribed an ad libitum dietary plan either advocating a fixed macronutrient composition or reduced or increased intake of one or more of the macronutrients. ...
... Each study prescribed an ad libitum dietary plan either advocating a fixed macronutrient composition or reduced or increased intake of one or more of the macronutrients. The prescription was either through provision of a menu (13,(18)(19)(20)(21)28,33,35,38,43,48,49,51), study shop (27,34,45,50) or dietary advice (22)(23)(24)(25)(26)(29)(30)(31)(32)36,(39)(40)(41)(42)44,46,47,(52)(53)(54). All studies manipulated the dietary composition using everyday foods with or without high quality protein supplements and so it was assumed that the food variety provided in each study did not result in nutritional imbalances such as an amino acid imbalance. ...
Increased energy intakes are contributing to overweight and obesity. Growing evidence supports the role of protein appetite in driving excess intake when dietary protein is diluted (the protein leverage hypothesis). Understanding the interactions between dietary macronutrient balance and nutrient-specific appetite systems will be required for designing dietary interventions that work with, rather than against, basic regulatory physiology. Data were collected from 38 published experimental trials measuring ad libitum intake in subjects confined to menus differing in macronutrient composition. Collectively, these trials encompassed considerable variation in percent protein (spanning 8-54% of total energy), carbohydrate (1.6-72%) and fat (11-66%). The data provide an opportunity to describe the individual and interactive effects of dietary protein, carbohydrate and fat on the control of total energy intake. Percent dietary protein was negatively associated with total energy intake (F = 6.9, P < 0.0001) irrespective of whether carbohydrate (F = 0, P = 0.7) or fat (F = 0, P = 0.5) were the diluents of protein. The analysis strongly supports a role for protein leverage in lean, overweight and obese humans. A better appreciation of the targets and regulatory priorities for protein, carbohydrate and fat intake will inform the design of effective and health-promoting weight loss diets, food labelling policies, food production systems and regulatory frameworks.
... Strategies to preserve skeletal muscle and improve physical function during weight loss should be prioritized. Currently, the addition of structured exercise is the most widely evidenced therapy to preserve lean mass during weight loss [3,9,10]. ...
Background and Aims
Weight loss without adequate anabolic stimuli can lead to reductions in lean, as well as adipose, tissue. Health benefits typically associated with weight loss are therefore attenuated, as body composition potentially shifts from an obese to sarcopenic/frail phenotype. In contrast to the traditional connotation of frailty, this might occur in younger adults and is characterized by reduced performance in functional tasks of daily living. Nutritional supplements as an adjunct to weight loss intervention could support the maintenance of lean mass, particularly if structured exercise is contraindicated. This systematic review aims to quantify the effect of nutritional supplements, without concurrent exercise, on lean mass in individuals undergoing pharmacological and nonpharmacological‐induced weight loss.
Methods
This protocol describes a prospective systematic review and meta‐analysis of randomized controlled trials investigating the effect of nutritional supplements on lean mass during weight loss. Comparison arms will not use nutritional supplements. Literature searches will be conducted using the following online databases: Embase, MEDLINE, Web of Science, Google Scholar, and OpenGrey. Outcome measures related to body composition, lean mass, skeletal muscle mass/size, or physical function will be extracted. Risk of bias will be assessed using the United States National Heart Lung and Blood Institute quality assessment tool for controlled intervention studies. A meta‐analysis will be conducted to synthesize comparable outcomes.
Results
The results of this review will be reported in adherence to PRISMA (Preferred Reporting Items for Systematic Review and Meta‐Analysis Protocols) standards, and published in a peer‐reviewed journal.
Conclusion
This study will be the first to systematically review nutritional interventions for the preservation or accretion of lean mass during weight loss. This review will identify gaps in the literature and inform the development of optimized weight loss strategies, for use in research and practice.
Trial Registration
International Prospective Register of Systematic Reviews: PROSPERO CRD42024521540.
... Even if muscle mass tends to decrease physiologically with age, we did not observe any reductions in fat-free mass and body cellular mass after both dietary regimes. Although a diet poor in carbohydrates may increase muscle catabolism [55], exacerbating fat-free mass loss during weight loss, the VLCKD preserved FFM and body cellular mass. The same result was seen after the MD. ...
The best nutritional strategy to fight the rise in obesity remains a debated issue. The Mediterranean diet (MD) and the Very Low-Calorie Ketogenic diet (VLCKD) are effective at helping people lose body weight (BW) and fat mass (FM) while preserving fat-free mass (FFM). This study aimed to evaluate the time these two diets took to reach a loss of 5% of the initial BW and how body composition was affected. We randomized 268 subjects with obesity or overweight in two arms, MD and VLCKD, for a maximum of 3 months or until they reached 5% BW loss. This result was achieved after one month of VLCKD and 3 months of MD. Both diets were effective in terms of BW (p < 0.0001) and FM loss (p < 0.0001), but the MD reached a higher reduction in both waist circumference (p = 0.0010) and FM (p = 0.0006) and a greater increase in total body water (p = 0.0017) and FFM (p = 0.0373) than VLCKD. The population was also stratified according to gender, age, and BMI. These two nutritional protocols are both effective in improving anthropometrical parameters and body composition, but they take different time spans to reach the goal. Therefore, professionals should evaluate which is the most suitable according to each patient’s health status.
... However, the review and meta-analysis of Ashtary-Larky et al. [8], which included 13 studies with a total of 244 participants undertaking RT training and KD diets, found significant reductions in FFM in the KD group. The loss of FFM in the meta-analysis of Ashtary-Larky [8] may be due to the fact that, of the thirteen studies evaluated, eight were carried out ad libitum [13,14,29,[32][33][34][35][36], and one of them did not report the nutritional data [37]. Therefore, only four studies included specific prescriptions for the consumption of total calories [12,27,28,38]. ...
Reviews focused on the ketogenic diet (KD) based on the increase in fat-free mass (FFM)
have been carried out with pathological populations or, failing that, without population differentiation. The aim of this review and meta-analysis was to verify whether a ketogenic diet without programmed energy restriction generates increases in fat-free mass (FFM) in resistance-trained participants. We evaluated the effect of the ketogenic diet, in conjunction with resistance training, on fat-free mass in trained participants. Boolean algorithms from various databases (PubMed, Scopus. and Web of Science) were used, and a total of five studies were located that related to both ketogenic diets and resistance-trained participants. In all, 111 athletes or resistance-trained participants (87 male and 24 female) were evaluated in the studies analyzed. We found no significant differences between groups in the FFM variables, and more research is needed to perform studies with similar ketogenic diets and control diet interventions. Ketogenic diets, taking into account the possible side effects, can
be an alternative for increasing muscle mass as long as energy surplus is generated; however, their application for eight weeks or more without interruption does not seem to be the best option due to the satiety and lack of adherence generated.
... Additionally, according to the role of SM glycogen synthesis in IS through Akt signaling (Russell, 2010;Kleinert et al., 2013;Yang, 2014), it could be inferred that increasing total SM mass will lead to a greater storage capacity . Collectively, it has been suggested that exercising toward SM hypertrophy (or maintenance of it in a context of weight loss) can therefore protect against metabolic syndrome and other metabolic diseases related to energy surplus (Ravussin and Bogardus, 1990;Wood et al., 2012). ...
Skeletal muscle (SM) tissue has been repetitively shown to play a major role in whole-body glucose homeostasis and overall metabolic health. Hence, SM hypertrophy through resistance training (RT) has been suggested to be favorable to glucose homeostasis in different populations, from young healthy to type 2 diabetic (T2D) individuals. While RT has been shown to contribute to improved metabolic health, including insulin sensitivity surrogates, in multiple studies, a universal understanding of a mechanistic explanation is currently lacking. Furthermore, exercised-improved glucose homeostasis and quantitative changes of SM mass have been hypothesized to be concurrent but not necessarily causally associated. With a straightforward focus on exercise interventions, this narrative review aims to highlight the current level of evidence of the impact of SM hypertrophy on glucose homeostasis, as well various mechanisms that are likely to explain those effects. These mechanistic insights could provide a strengthened rationale for future research assessing alternative RT strategies to the current classical modalities, such as low-load, high repetition RT or high-volume circuit-style RT, in metabolically impaired populations.
... This preservation of motor function was associated with higher relative weights of several hind limb muscles in old mice on the KD. In humans, the KD has a protective effect on muscle mass compared to a low-fat diet during weight loss in the absence of exercise (Wood et al., 2012). There is currently limited knowledge about the effect of the KD on cellular mechanisms in skeletal muscle, although prior investigations in young rodents have demonstrated a rise in markers of mitochondrial content and biogenesis (Hyatt et al., 2016;Parry et al., 2018), an increase in antioxidant protein expression (Hyatt et al., 2016) and a decrease in young (5 months) but an increase in old (28 months) rats in relation to anabolic signaling through the mTOR pathway (Bennett et al., 2019). ...
The causes of the decline in skeletal muscle mass and function with age, known as sarcopenia, are poorly understood. Nutrition (calorie restriction) interventions impact many cellular processes and increase lifespan and preserve muscle mass and function with age. As we previously observed an increase in life span and muscle function in aging mice on a ketogenic diet (KD), we aimed to investigate the effect of a KD on the maintenance of skeletal muscle mass with age and the potential molecular mechanisms of this action. Twelve‐month‐old mice were assigned to an isocaloric control or KD until 16 or 26 months of age, at which time skeletal muscle was collected for evaluating mass, morphology, and biochemical properties. Skeletal muscle mass was significantly greater at 26 months in the gastrocnemius of mice on the KD. This result in KD mice was associated with a shift in fiber type from type IIb to IIa fibers and a range of molecular parameters including increased markers of NMJ remodeling, mitochondrial biogenesis, oxidative metabolism, and antioxidant capacity, while decreasing endoplasmic reticulum (ER) stress, protein synthesis, and proteasome activity. Overall, this study shows the effectiveness of a long‐term KD in mitigating sarcopenia. The diet preferentially preserved oxidative muscle fibers and improved mitochondrial and antioxidant capacity. These adaptations may result in a healthier cellular environment, decreasing oxidative and ER stress resulting in less protein turnover. These shifts allow mice to better maintain muscle mass and function with age.
... The titles and abstracts from the initial screening were reviewed and 3007 studies, which were review studies, pilot studies, or not related to this meta-analysis, were excluded. Full texts of the remaining 38 studies were reviewed to determine eligibility, and finally, seven studies were selected [16][17][18][19][20][21]. A total of 255 overweight and obese individuals were included in this meta-analysis. ...
Abstract: (1) Background: The purpose of this meta-analysis was to investigate the effects of combined exercise and low carbohydrate ketogenic diet interventions (CELCKD) for overweight and obese individuals. (2) Methods: Relevant studies were searched by using the MEDLINE and EMBASE databases up to October 2020. Study Inclusion and Exclusion Criteria: Inclusion criteria were reporting effects of the CELCKD for overweight and obese individuals from randomized controlled trials. Studies that did not match the inclusion criteria were excluded. The methods for CELCKD and outcomes of selected studies were extracted. The effect sizes for interventions that included ardiorespiratory fitness, body composition, fasting glucose, and lipid profiles were calculated by using the standardized mean difference statistic. (3) Results: A total of seven studies and 278 overweight and obese individuals were included. The average intervention of selected studies consisted of moderate to vigorous intensity, 4 times per week for 9.2 weeks. Participating in CELCKD interventions was decreased triglycerides (d = 0.34, CI; 0.68–0.01, p = 0.04) and waist circumference (d = 0.74, 95% confidence interval [CI]; 1.28–1.20, p = 0.01), while cardiovascular fitness, body composition, fasting glucose, total cholesterol, high density lipoprotein (HDL) cholesterol, and low density lipoprotein (LDL) cholesterol were not statistically different after the interventions. No adverse side effects were reported. (4) Conclusions: Participation in interventions by overweight and obese individuals had beneficial effects including decreased waist circumference and triglycerides. Longer term intervention studies with homogenous control groups may be needed.
... A large body of literature suggests the diet effectively induces fat loss in both untrained (10-12,40,41,42, 57,61,71,76,85) and trained populations (29, 63,68,87,92,93). The studies reveal that the KD promotes equal or superior fat mass loss compared to control diets. ...
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.
... Our results support previous studies which demonstrate that the addition of combined exercise training during low-carbohydrate diet is able to attenuate [50] or even completely eliminate the expected LMM loss [15]. This could be mostly attributed to the resistance exercise component of the exercise intervention and its effect on increasing muscle mass [51]. It is, however, difficult to quantify the need for muscle mass retention. ...
Background:
Low-carbohydrate (LC) diets are an effective method for treating obesity and reducing cardiometabolic risk. However, exposure to LC diets is associated with reductions in muscle mass and increased osteoporosis risk in obese individuals. The combination of exercise with a LC diet appears to attenuate muscle mass loss induced by LC diets alone, and to further improve cardiometabolic profile. However, evidence to date in obese individuals is limited. We assessed the effect of LC diet in combination with supervised exercise on cardiorespiratory fitness, body composition and cardiometabolic risk factors in obese individuals. Methods: Male and female participants in the experimental (EX-LC; structured supervised exercise program + low-carbohydrate meals; n = 33; 35.3 years) and control (EX-CO; structured supervised exercise program + standard dietary advice; n = 31; 34.2 years) conditions underwent measurements of cardiorespiratory fitness (VO2peak), body fat, lean muscle mass (LMM), and cardiometabolic biomarkers before and after an 8 week intervention. Results: Participants in the EX-LC condition demonstrated greater improvements in VO2peak (p = 0.002) and fat mass index (FMI, p = 0.001) compared to the EX-CO condition. Achieving a ketogenic state (β-hydroxybutyrate, βHB ≥0.3 mmol/L) was associated with greater reductions in total body fat (p = 0.011), visceral adipose tissue (p = 0.025), FMI (p = 0.002) and C-reactive protein (CRP, p = 0.041) but also with greater reductions in LMM (p = 0.042). Conclusion: Short-term LC diet combined with prescribed exercise enhanced cardiorespiratory fitness and the cardiometabolic profile of obese individuals but was also associated with greater muscle mass loss compared to similar exercise training and standard dietary advice. The long-term effects of the LC diet should be further explored in future studies.
... can deter the loss of fat-free mass typically seen in individuals following a KD (59,60). Whether KDs possess an anabolic property is an intriguing question given that there is a strong positive relationship between dietary fat and plasma testosterone levels (61). ...
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.
... In another study, authors showed a similar decrease in lean body mass during KD with resistance training, KD without training and low fat diet with resistance training, while the loss of muscle mass was greater after a low fat diet without resistance training suggesting a protective effect of KD on muscle mass compared to a low fat diet in absence of training (Wood et al., 2012). Moreover, a recent paper investigating the effects of KD on body composition and performance in weight lifters found a decrease in lean body mass without negative effects on specific sport's performance (Greene et al., 2018). ...
Ketogenic diet (KD) is a nutritional regimen characterized by a high-fat and an adequate protein content and a very low carbohydrate level (less than 20 g per day or 5% of total daily energy intake). The insufficient level of carbohydrates forces the body to primarily use fat instead of sugar as a fuel source. Due to its characteristic, KD has often been used to treat metabolic disorders, obesity, cardiovascular disease, and type 2 diabetes. Skeletal muscle constitutes 40% of total body mass and is one of the major sites of glucose disposal. KD is a well-defined approach to induce weight loss, with its role in muscle adaptation and muscle hypertrophy less understood. Considering this lack of knowledge, the aim of this review was to examine the scientific evidence about the effects of KD on muscle hypertrophy. We first described the mechanisms of muscle hypertrophy per se, and secondly, we discussed the characteristics and the metabolic function of KD. Ultimately, we provided the potential mechanism that could explain the influence of KD on skeletal muscle hypertrophy.
... However, it is typically observed that a CRD promotes higher reductions in triacylglycerol and increases in HDL-c levels compared to conventional diets 22,25 . Wood et al. 27 also reported that improvements in HDL-c were better in the CRD group versus the low-fat diet group after 12 weeks of hypoenergetic diets with progressive resistance training. ...
Objective:
To compare the effects of either a carbohydrate-restrictive diets or a conventional hypoenergetic diet combined with resistance training.
Methods:
Twenty-one overweight and obese adults participated in an eight-week program consisting of progressive resistance training combined with carbohydrate-restrictive diets (initially set at <30 g carbohydrate; n=12) or conventional hypoenergetic diet (30% energetic restriction; carbohydrate/protein/lipid: 51/18/31% of total energy consumption; n=9). It was hypothesized that the carbohydrate-restrictive diets would induce greater weight loss but that both diets would elicit similar effects on selected health markers. Body mass, and body composition, blood variables and flow-mediated brachial artery dilation (flow-mediated brachial artery dilation; by ultrasound) were used to assess changes due to the interventions.
Results:
Significant within-group reductions in body mass (-5.4±3.5%; p=0.001 versus -3.7±3.0%; p=0.015) and body fat (body fat; -10.2±7.0%; p=0.005 versus -9.6±8.8%; p=0.017) were identified for carbohydrate-restrictive diets and conventional hypoenergetic diet, respectively, but there were no significant differences between groups as the result of the interventions. Fat free mass, blood variables and flow-mediated brachial artery dilation did not significantly change, except for the total cholesterol/high-density lipoprotein ratio, which was reduced 10.4±16.9% in carbohydrate-restrictive diets (p=0.037) and 0.5±11.3% in conventional hypoenergetic diet (p=0.398).
Conclusion:
Carbohydrate-restrictive diets associated with resistance training was as effective as conventional hypoenergetic diet in decreasing body mass and body fat, as well as maintaining fat free mass, blood variables and flow-mediated brachial artery dilation, however it was more effective at lowering the total cholesterol/low density lipoprotein ratio.
Weight loss treatments require adherence to physical exercise and diet. Restrictive diets have been proposed for obesity treatment, including a ketogenic diet that are high in lipids, moderate in proteins, and low in carbohydrates. In recent years, there has been criticism of this diet because of the reduction in fat-free mass and, consequently, a reduction in basal energy expenditure, which is considered negative in obesity treatment. However, resistance training is known to promote skeletal muscle hypertrophy. The hypothesis for this review was: "Resistance training is sufficient to maintain lean mass during diets that cause ketosis." Despite the slight reduction in lean mass identified in the meta-analysis, some authors reported no loss in physical performance. Others suggested that this difference in lean mass is associated with water loss in the participants, which aligns with a few studies that reported a final phase with carbohydrate reintroduction into the diet. Our results indicated physical exercise was an important tool for maintaining lean mass in individuals who consumed carbohydrate-restricted diets that cause ketosis.
Keywords: high-fat diet; carbohydrate-restricted diet; body composition; physical activity; muscle hypertrophy.
Carbohydrate restriction has gained increasing popularity as an adjunctive nutritional therapy for diabetes management. However, controversy remains regarding the long-term suitability, safety, efficacy and potential superiority of a very low carbohydrate, ketogenic diet compared to current recommended nutritional approaches for diabetes management. Recommendations with respect to a ketogenic diet in clinical practice are often hindered by the lack of established definition, which prevents its capacity to be most appropriately prescribed as a therapeutic option for diabetes. Furthermore, with conflicted evidence, this has led to uncertainty amongst clinicians on how best to support and advise their patients. This review will explore whether a ketogenic diet has a place within clinical practice by reviewing current evidence and controversies.
Aims
We performed a systematic review and meta-analysis to compare the effects of Ex (exercise training) vs. DI (dietary intervention) vs. combined Ex and DI interventions on total cholesterol (TC), low-density lipoprotein cholesterol (LDL), triglycerides (TG), and high-density lipoprotein cholesterol (HDL), in adults with overweight and obesity.
Data synthesis
PubMed, Web of Science, and Scopus were searched to identify original articles through to March 2022, using keywords for the categories “exercise training”, “dietary intervention”, “overweight and obesity” and “randomized.” Studies that included lipid profiles as outcomes and performed in adults with body mass indexes (BMI) ≥ 25 kg/m2 were included. A total of 80 studies involving 4,804 adult participants were included in the meta-analysis. Ex was not as effective as DI for reducing TC and TG, and was less effective for reducing LDL. In addition, Ex increased HDL to a greater extent than DI. Combined interventions decreased TC, TG and LDL, but did not increase HDL more than Ex alone. Combined interventions failed to reduce TC or LDL, but decreased TG and increased HDL more than DI alone.
Conclusions
Our results suggest that the combination of Ex and DI can be more effective than either Ex or DI alone in improving lipid profiles in adults with overweight and obesity.
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.
Short‐term energy deficits impair anabolic hormones and muscle protein synthesis. However, the effects of prolonged energy deficits on resistance training (RT) outcomes remain unexplored. Thus, we conducted a systematic review of PubMed and SportDiscus for randomized controlled trials performing RT in an energy deficit (RT+ED) for ≥3 weeks. We first divided the literature into studies with a parallel control group without an energy deficit (RT+CON; Analysis A) and studies without RT+CON (Analysis B). Analysis A consisted of a meta‐analysis comparing gains in lean mass (LM) and strength between RT+ED and RT+CON. Studies in Analysis B were matched with separate RT+CON studies for participant and intervention characteristics, and we qualitatively compared the gains in LM and strength between RT+ED and RT+CON. Finally, Analyses A and B were pooled into a meta‐regression examining the relationship between the magnitude of the energy deficit and LM. Analysis A showed LM gains were impaired in RT+ED vs RT+CON (effect size (ES) = ‐0.57, p = .02), but strength gains were comparable between conditions (ES = ‐0.31, p = .28). Analysis B supports the impairment of LM in RT+ED (ES: ‐0.11, p = .03) vs RT+CON (ES: 0.20, p < .001) but not strength (RT+ED ES: 0.84; RT+CON ES: 0.81). Finally, our meta‐regression demonstrated that an energy deficit of ~500 kcal · day‐1 prevented gains in LM. Individuals performing RT to build LM should avoid prolonged energy deficiency, and individuals performing RT to preserve LM during weight loss should avoid energy deficits >500 kcal · day‐1.
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.
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.
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.
(1) Objective: to establish practical guidance for the design of future clinical trials in MS (metabolic syndrome) patients aged 18 and older, based on a systematic review of randomized clinical trials connecting diet, physical exercise and changes in body composition. (2) Method: this systematic review of randomized clinical trials (RCT) is based on the guidelines recommended by PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses). Criteria of selection: ≥18 years of age; patients diagnosed with MS; intervention programs including diet, physical exercise and/or modifications in the style of life as treatment, as well as the magnitude of changes in body composition (BC); randomized clinical trial published between 2004 and 2018. (3) Results: the multidisciplinary interventions describe major changes in BC, and the recurring pattern in these clinical trials is an energy reduction and control in the percentage of intake of macronutrients along with the performance of regularly structured exercise; the most analyzed parameter was waist circumference (88.9% of the trials), followed by body weight (85.2%), BMI (77.8%) and body fat (55.6%). (4) Conclusions: The analysis of the information here reported sheds light for the design of future clinical trials in adults with MS. The best anthropometric parameters and units of measurement to monitor the interventions are related to dietary and physical exercise interventions. A list of practical advice that is easy to implement in daily practice in consultation is here proposed in order to guarantee the best results in changes of body composition.
Background/Objectives
Regular exercise training is effective to altering many markers of metabolic syndrome and its effects are strongly influenced by the type of consumed diet. Nowadays, resistance training (RT) has been frequently associated with low-carbohydrate high-fat diet (LCD). After long term these diets causes body weight (BW) regain with deleterious effects on body composition and metabolic risk factors. The effects of RT associated with long-term LCD on these parameters remain unexplored. We aimed to investigate the effects of RT when associated with long-term LCD on BW, feed efficiency, body composition, glucose homeostasis, liver parameters and serum biochemical parameters during BW regain period in rats.
Subjects/Methods
Male Sprague–Dawley rats were fed with LCD (LC groups) or standard diet (STD) (ST groups). After 10 weeks-diet animals were separated into sedentary (Sed-LC and Sed-ST) and resistance-trained (RT-LC and RT-ST) groups (N = 8/group). RT groups performed an 11-week climbing program on a ladder with progressive load. Dual x-ray absorptiometry, glucose tolerance tests and insulin tolerance tests were performed at weeks 10 and 20. Liver and serum were collected at week 21.
Results
RT reduced feed efficiency, BW gain, liver fat and total and LDL cholesterol, and improved body composition and glucose clearance in animals fed on STD. In those fed with LCD, RT reduced caloric intake, BW regain, liver fat and serum triglycerides levels. However, improvement in body composition was inhibited and bone mineral density and glucose clearance was further impaired in this association.
Conclusions
The LCD nullifies the beneficial effects of RT on body composition, glucose homeostasis and impairs some health parameters. Our results do not support the association of RT with LCD in a long term period.
The prevalence of obesity in combination with sarcopenia (the age-related loss of muscle mass and strength or physical function) is increasing in adults aged 65 years and older. A major subset of adults over the age of 65 is now classified as having sarcopenic obesity, a high-risk geriatric syndrome predominantly observed in an ageing population that is at risk of synergistic complications from both sarcopenia and obesity. This Review discusses pathways and mechanisms leading to muscle impairment in older adults with obesity. We explore sex-specific hormonal changes, inflammatory pathways and myocellular mechanisms leading to the development of sarcopenic obesity. We discuss the evolution, controversies and challenges in defining sarcopenic obesity and present current body composition modalities used to assess this condition. Epidemiological surveys form the basis of defining its prevalence and consequences beyond comorbidity and mortality. Current treatment strategies, and the evidence supporting them, are outlined, with a focus on calorie restriction, protein supplementation and aerobic and resistance exercises. We also describe weight loss-induced complications in patients with sarcopenic obesity that are relevant to clinical management. Finally, we review novel and potential future therapies including testosterone, selective androgen receptor modulators, myostatin inhibitors, ghrelin analogues, vitamin K and mesenchymal stem cell therapy.
The anabolic effect of resistance training can mitigate muscle loss during contest preparation. In reviewing relevant literature, we recommend a periodized approach be utilized. Block and undulating models show promise. Muscle groups should be trained 2 times weekly or more, although high volume training may benefit from higher frequencies to keep volume at any one session from becoming excessive. Low to high (~3--15) repetitions can be utilized but most repetitions should occur in the 6--12 range using 70--80% of 1 repetition maximum. Roughly 40--70 reps per muscle group per session should be performed, however higher volume may be appropriate for advanced bodybuilders. Traditional rest intervals of 1--3 minutes are adequate, but longer intervals can be used. Tempo should allow muscular control of the load;; 1-- 2sec concentric and 2--3sec eccentric tempos. Training to failure should be limited when performing heavy loads on taxing exercises, and primarily relegated to single--joint exercises and higher repetitions. A core of multi--joint exercises with some single--joint exercises to address specific muscle groups as needed should be used, emphasizing full range of motion and proper form. Cardiovascular training can be used to enhance fat loss. Interference with strength training adaptations increases concomitantly with frequency and duration of cardiovascular training. Thus, the lowest frequency and duration possible while achieving sufficient fat loss should be used. Full--body modalities or cycling may reduce interference. High intensities may as well;; however, require more recovery. Fasted cardiovascular training may not have benefits over fed--state and could be detrimental.
Abstract
Metabolic Syndrome (MetS) represents a constellation of markers that indicates a predisposition to diabetes, cardiovascular disease and other pathologic states. The definition and treatment are a matter of current debate and there is not general agreement on a precise definition or, to some extent, whether the designation provides more information than the individual components. We consider here five indicators that are central to most definitions and we provide evidence from the literature that these are precisely the symptoms that respond to reduction in dietary carbohydrate (CHO). Carbohydrate restriction is one of several strategies for reducing body mass but even in the absence of weight loss or in comparison with low fat alternatives, CHO restriction is effective at ameliorating high fasting glucose and insulin, high plasma triglycerides (TAG), low HDL and high blood pressure. In addition, low fat, high CHO diets have long been known to raise TAG, lower HDL and, in the absence of weight loss, may worsen glycemic control. Thus, whereas there are numerous strategies for weight loss, a patient with high BMI and high TAG is likely to benefit most from a regimen that reduces CHO intake. Reviewing the literature, benefits of CHO restriction are seen in normal or overweight individuals, in normal patients who meet the criteria for MetS or in patients with frank diabetes. Moreover, in low fat studies that ameliorate LDL and total cholesterol, controls may do better on the symptoms of MetS. On this basis, we feel that MetS is a meaningful, useful phenomenon and may, in fact, be operationally defined as the set of markers that responds to CHO restriction. Insofar as this is an accurate characterization it is likely the result of the effect of dietary CHO on insulin metabolism. Glucose is the major insulin secretagogue and insulin resistance has been tied to the hyperinsulinemic state or the effect of such a state on lipid metabolism. The conclusion is probably not surprising but has not been explicitly stated before. The known effects of CHO-induced hypertriglyceridemia, the HDL-lowering effect of low fat, high CHO interventions and the obvious improvement in glucose and insulin from CHO restriction should have made this evident. In addition, recent studies suggest that a subset of MetS, the ratio of TAG/HDL, is a good marker for insulin resistance and risk of CVD, and this indicator is reliably reduced by CHO restriction and exacerbated by high CHO intake. Inability to make this connection in the past has probably been due to the fact that individual responses have been studied in isolation as well as to the emphasis of traditional therapeutic approaches on low fat rather than low CHO.
We emphasize that MetS is not a disease but a collection of markers. Individual physicians must decide whether high LDL, or other risk factors are more important than the features of MetS in any individual case but if MetS is to be considered it should be recognized that reducing CHO will bring improvement. Response of symptoms to CHO restriction might thus provide a new experimental criterion for MetS in the face of on-going controversy about a useful definition. As a guide to future research, the idea that control of insulin metabolism by CHO intake is, to a first approximation, the underlying mechanism in MetS is a testable hypothesis.
We recently proposed that the biological markers improved by carbohydrate restriction were precisely those that define the metabolic syndrome (MetS), and that the common thread was regulation of insulin as a control element. We specifically tested the idea with a 12-week study comparing two hypocaloric diets (approximately 1,500 kcal): a carbohydrate-restricted diet (CRD) (%carbohydrate:fat:protein = 12:59:28) and a low-fat diet (LFD) (56:24:20) in 40 subjects with atherogenic dyslipidemia. Both interventions led to improvements in several metabolic markers, but subjects following the CRD had consistently reduced glucose (-12%) and insulin (-50%) concentrations, insulin sensitivity (-55%), weight loss (-10%), decreased adiposity (-14%), and more favorable triacylglycerol (TAG) (-51%), HDL-C (13%) and total cholesterol/HDL-C ratio (-14%) responses. In addition to these markers for MetS, the CRD subjects showed more favorable responses to alternative indicators of cardiovascular risk: postprandial lipemia (-47%), the Apo B/Apo A-1 ratio (-16%), and LDL particle distribution. Despite a threefold higher intake of dietary saturated fat during the CRD, saturated fatty acids in TAG and cholesteryl ester were significantly decreased, as was palmitoleic acid (16:1n-7), an endogenous marker of lipogenesis, compared to subjects consuming the LFD. Serum retinol binding protein 4 has been linked to insulin-resistant states, and only the CRD decreased this marker (-20%). The findings provide support for unifying the disparate markers of MetS and for the proposed intimate connection with dietary carbohydrate. The results support the use of dietary carbohydrate restriction as an effective approach to improve features of MetS and cardiovascular risk.
To determine if physical training conserves fat-free mass (FFM) in overweight men or women during weight loss.
Journals published between 1966 and 1993 were searched by MEDLINE and by handsearch to obtain all reports on human subjects in which the effect of exercise on body composition was studied in at least two concurrent treatment groups, of which at least one group did, and one group did not, undergo an exercise programme designed to promote fat loss. The relation between loss of weight, and loss of FFM, was examined by linear regression analysis among exercising and non-exercising groups of men or women.
Twenty-eight publications reported results on 226 sedentary men in 13 groups, 233 exercising men in 14 groups, 199 sedentary women in 23 groups, and 258 exercising women in 28 groups.
Aerobic exercise without dietary restriction among men caused a weight loss of 3 kg in 30 weeks compared with sedentary controls, and 1.4 kg in 12 weeks among women, but there was little effect on FFM. Resistance exercise had little effect on weight loss, but increased FFM by about 2 kg in men and 1 kg in women. Regression analysis shows that for a weight loss of 10 kg by diet alone the expected loss of FFM is 2.9 kg in men and 2.2 kg in women. When similar weight loss is achieved by exercise combined with dietary restriction the expected loss of FFM is reduced to 1.7 kg in men, and women. It is probable that the FFM conserved by exercise during weight loss contains more water and potassium than average FFM. The subjects studied were not severely obese.
Aerobic exercise causes a modest loss in weight without dieting. Exercise provides some conservation of FFM during weight loss by dieting, probably in part by maintaining glycogen and water.
Aging is associated with a redistribution of both fat and lean tissue within the body. Intra-abdominal fat (IAF) accumulates more rapidly than total fat while the loss of lean body mass is mostly due to sarcopenia. Increase of visceral fat plays a major role in the pathogenesis of insulin resistance, which leads to type II diabetes and also to cardiovascular diseases. This review is focussed on the relationships that exist between the accumulation of IAF and insulin resistance during aging. The various methods available for assessing IAF are briefly reviewed; imaging techniques are the only reference methods, and their availability is limited. Insulin resistance that appears with aging is caused by accumulation of IAF, rather than by aging per se. Studies done in type II diabetic patients suggest that the metabolic link between increased IAF and insulin resistance could well be the increased availability and/or oxidation of free fatty acids. Physical inactivity certainly enhances both IAF accumulation and, more directly, insulin resistance. Independent and significant effects of menopause or of sarcopenia on insulin resistance remain to be established. The influence of hormonal changes, reduced fatty acid utilization, and resistance to leptin on IAF accumulation are also discussed. Although it is difficult to determine the independent influence of each of these factors, IAF accumulation seems to be a central and important determinant of cardiovascular risk. The last part of this review is devoted to protein metabolism and focused on the preservation of protein metabolism in the liver during aging.
5'-AMP-activated protein kinase (AMPK) functions as a metabolic switch in mammalian cells and can be artificially activated by 5-aminoimidazole-4-carboxamide (AICA)-riboside. AMPK activation during muscle contraction is dependent on muscle glycogen concentrations, but whether glycogen also modifies the activation of AMPK and its possible downstream effectors (glycogen synthase and glucose transport) by AICA-riboside in resting muscle is not known. Thus, we have altered muscle glycogen levels in rats by a combination of swimming exercise and diet and investigated the effects of AICA-riboside in the perfused rat hindlimb muscle. Two groups of rats, one with super-compensated muscle glycogen content (approximately 200-300% of normal; high glycogen [HG]) and one with moderately lowered muscle glycogen content (approximately 80% of normal; low glycogen [LG]), were generated. In both groups, the degree of activation of the alpha2 isoform of AMPK by AICA-riboside depended on muscle type (white gastrocnemius > red gastrocnemius > soleus). Basal and AICA-riboside-induced alpha2-AMPK activity were markedly lowered in the HG group (approximately 50%) compared with the LG group. Muscle 2-deoxyglucose uptake was also increased and glycogen synthase activity decreased by AICA-riboside. Especially in white gastrocnemius, these effects, as well as the absolute activity levels of AMPK-alpha2, were markedly reduced in the HG group compared with the LG group. The inactivation of glycogen synthase by AICA-riboside was accompanied by decreased gel mobility and was eliminated by protein phosphatase treatment. We conclude that acute AICA-riboside treatment leads to phosphorylation and deactivation of glycogen synthase in skeletal muscle. Although the data do not exclude a role of other kinases/phosphatases, they suggest that glycogen synthase may be a target for AMPK in vivo. Both basal and AICA-riboside-induced AMPK-alpha2 and glycogen synthase activities, as well as glucose transport, are depressed when the glycogen stores are plentiful. Because the glycogen level did not affect adenine nucleotide concentrations, our data suggest that glycogen may directly affect the activation state of AMPK in skeletal muscle.
Low muscle strength is associated with mortality, presumably as a result of low muscle mass (sarcopenia) and physical inactivity. Grip strength was longitudinally collected in 1071 men over a 25-year period. Muscle mass was estimated by using 24-hour creatinine excretion and physical activity values, obtained by questionnaire. Survival analysis examined the impact of grip strength and rate of change in strength on all-cause mortality over 40 years. Lower and declining strength are associated with increased mortality, independent of physical activity and muscle mass. In men <60 years, rate of loss of strength was more important than the actual levels. In men >/=60 years, strength was more protective than the rate of loss, which persisted when muscle mass was considered. Strength and rate of change in strength contribute to the impact of sarcopenia on mortality. Although muscle mass and physical activity are important, they do not completely account for the impact of strength and changes in strength.
We tested the hypothesis that IL-6 release from muscle during exercise may be related to muscle activity of 5'-AMP-activated protein kinase (AMPK). Eight healthy, well-trained young men completed two 60-min trials on a bicycle ergometer at 70% of their peak oxygen uptake in either a glycogen-depleted or a glycogen-loaded state. IL-6 was released from the leg already after 10 min of exercise in the glycogen-depleted state, whereas no significant release was observed at any time in the loaded state. Nevertheless, plasma IL-6 increased similarly in the two trials from approximately 0.8 pg/ml at rest to approximately 4.5 pg/ml after 60 min of exercise. Activity of alpha1-AMPK (160%) and alpha2-AMPK (145%) was increased at rest in the glycogen-depleted compared with the loaded situation. During exercise, alpha1-AMPK activity did not change from resting levels in both trials, whereas alpha2-AMPK activity increased only in the glycogen-depleted state. After 60 min of exercise in the glycogen-depleted state, individual values of alpha2-AMPK activity correlated significantly (r = 0.87, P < 0.006) with individual values of IL-6 release as well as with average IL-6 release over the entire 60 min (r = 0.86, P < 0.006). The present data are compatible with a role for AMPK in IL-6 release during exercise or a role for IL-6 in activating AMPK. Alternatively, both AMPK and IL-6 are independent sensors of a low muscle glycogen concentration during exercise. In addition, leg release of IL-6 cannot alone explain the increase in plasma IL-6 during exercise.
Magnetic resonance spectroscopy studies have shown that intramyocellular lipids (IMCL) and liver fat (LFAT) levels vary with insulin sensitivity and obesity, which are common in the elderly. Thus, magnetic resonance spectroscopy was used to investigate the hypothesis that IMCL and LFAT are increased in the elderly. IMCL and LFAT in young (aged 20-32 yr) and elderly (aged 65-74 yr) were measured fasted, and glucose, insulin, total free fatty acids levels, and free fatty acids profiles were measured during a 2-h oral glucose tolerance test. Body fat percentage was determined with dual x-ray absorptiometry. The elderly had significantly greater IMCL (0.12 +/- 0.01 vs. 0.08 +/- 0.01, mean +/- sem; P = 0.01) and LFAT (0.28 +/- 0.06 vs. 0.08 +/- 0.01; P = 0.004; expressed as ratios to Intralipid standard) than the young. The elderly had increased insulin resistance as calculated by the Matsuda model compared with the young (5.1 +/- 0.9 vs. 9.9 +/- 1.4; P = 0.02). Regression analysis of all subjects indicated that the increases in IMCL and LFAT were correlated with insulin sensitivity, glycosylated hemoglobin, plasma lipids, and body fat. Furthermore, the correlation between insulin sensitivity and IMCL and LFAT remained significant, after accounting for the effect of body fat. Increases of IMCL and LFAT occur in elderly individuals and may be related to insulin resistance.
The prevalence of the metabolic syndrome is high among U.S. adults. Our purpose was to determine whether the prevalence of this syndrome has changed since 1988-1994.
A total of 6,436 men and women aged > or = 20 years from the National Health and Nutrition Examination Survey (NHANES) III (1988-1994) and 1,677 participants from NHANES 1999-2000 were included in the analyses. We used the definition of the metabolic syndrome developed by the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults.
The unadjusted prevalence of the metabolic syndrome was 23.1% in NHANES III and 26.7% in NHANES 1999-2000 (P = 0.043), and the age-adjusted prevalences were 24.1 and 27.0% (P = 0.088), respectively. The age-adjusted prevalence increased by 23.5% among women (P = 0.021) and 2.2% among men (P = 0.831). Increases in high blood pressure, waist circumference, and hypertriglyceridemia accounted for much of the increase in the prevalence of the metabolic syndrome, particularly among women.
The increased prevalence of the metabolic syndrome is likely to lead to future increases in diabetes and cardiovascular disease.
Lower muscle mass has been correlated with poor physical function; however, no studies have examined this relationship prospectively. This study aims to investigate whether low muscle mass, low muscle strength, and greater fat infiltration into the muscle predict incident mobility limitation.
Our study cohort included 3075 well-functioning black and white men and women aged 70-79 years participating in the Health, Aging, and Body Composition study. Participants were followed for 2.5 years. Muscle cross-sectional area and muscle tissue attenuation (a measure of fat infiltration) were measured by computed tomography at the mid-thigh, and knee extensor strength by using a KinCom dynamometer. Incident mobility limitation was defined as two consecutive self-reports of any difficulty walking one-quarter mile or climbing 10 steps.
Mobility limitations were developed by 22.3% of the men and by 31.8% of the women. Cox's proportional hazards models, adjusting for demographic, lifestyle, and health factors, showed a hazard ratio of 1.90 [95% confidence interval (CI), 1.27-2.84] in men and 1.68 (95% CI, 1.23-2.31) in women for the lowest compared to the highest quartile of muscle area (p <.01 for trend). Results for muscle strength were 2.02 (95% CI, 1.39-2.94) and 1.91 (95% CI, 1.41-2.58), p <.001 trend, and for muscle attenuation were 1.91 (95% CI, 1.31-2.83) and 1.68 (95% CI, 1.20-2.35), p <.01 for trend. When included in one model, only muscle attenuation and muscle strength independently predicted mobility limitation (p < .05). Among men and women, associations were similar for blacks and whites.
Lower muscle mass (smaller cross-sectional thigh muscle area), greater fat infiltration into the muscle, and lower knee extensor muscle strength are associated with increased risk of mobility loss in older men and women. The association between low muscle mass and functional decline seems to be a function of underlying muscle strength.
Metabolic Syndrome (MetS) represents a constellation of markers that indicates a predisposition to diabetes, cardiovascular disease and other pathologic states. The definition and treatment are a matter of current debate and there is not general agreement on a precise definition or, to some extent, whether the designation provides more information than the individual components. We consider here five indicators that are central to most definitions and we provide evidence from the literature that these are precisely the symptoms that respond to reduction in dietary carbohydrate (CHO). Carbohydrate restriction is one of several strategies for reducing body mass but even in the absence of weight loss or in comparison with low fat alternatives, CHO restriction is effective at ameliorating high fasting glucose and insulin, high plasma triglycerides (TAG), low HDL and high blood pressure. In addition, low fat, high CHO diets have long been known to raise TAG, lower HDL and, in the absence of weight loss, may worsen glycemic control. Thus, whereas there are numerous strategies for weight loss, a patient with high BMI and high TAG is likely to benefit most from a regimen that reduces CHO intake. Reviewing the literature, benefits of CHO restriction are seen in normal or overweight individuals, in normal patients who meet the criteria for MetS or in patients with frank diabetes. Moreover, in low fat studies that ameliorate LDL and total cholesterol, controls may do better on the symptoms of MetS. On this basis, we feel that MetS is a meaningful, useful phenomenon and may, in fact, be operationally defined as the set of markers that responds to CHO restriction. Insofar as this is an accurate characterization it is likely the result of the effect of dietary CHO on insulin metabolism. Glucose is the major insulin secretagogue and insulin resistance has been tied to the hyperinsulinemic state or the effect of such a state on lipid metabolism. The conclusion is probably not surprising but has not been explicitly stated before. The known effects of CHO-induced hypertriglyceridemia, the HDL-lowering effect of low fat, high CHO interventions and the obvious improvement in glucose and insulin from CHO restriction should have made this evident. In addition, recent studies suggest that a subset of MetS, the ratio of TAG/HDL, is a good marker for insulin resistance and risk of CVD, and this indicator is reliably reduced by CHO restriction and exacerbated by high CHO intake. Inability to make this connection in the past has probably been due to the fact that individual responses have been studied in isolation as well as to the emphasis of traditional therapeutic approaches on low fat rather than low CHO.
We emphasize that MetS is not a disease but a collection of markers. Individual physicians must decide whether high LDL, or other risk factors are more important than the features of MetS in any individual case but if MetS is to be considered it should be recognized that reducing CHO will bring improvement. Response of symptoms to CHO restriction might thus provide a new experimental criterion for MetS in the face of on-going controversy about a useful definition. As a guide to future research, the idea that control of insulin metabolism by CHO intake is, to a first approximation, the underlying mechanism in MetS is a testable hypothesis.
Background:
Obesity exacerbates the age-related decline in physical function and causes frailty in older persons. However, appropriate treatment for obese older persons is unknown. We evaluated the effects of weight loss and exercise therapy on physical function and body composition in obese older persons.
Methods:
We screened 40 obese older volunteers and eventually randomized 27 frail obese older volunteers to treatment or control groups. Treatment consisted of 6 months of weekly behavioral therapy for weight loss in conjunction with exercise training 3 times per week. Physical function was evaluated with measurements of frailty (Physical Performance Test, peak oxygen consumption, and Functional Status Questionnaire); strength, gait, and balance tests; body composition with dual-energy x-ray absorptiometry; and quality of life using the Medical Outcomes Survey 36-Item Short-Form Health Survey. Results are reported as mean +/- SD.
Results:
Two subjects in the treatment group did not comply with the intervention, and 1 subject in the control group withdrew. Analyses included all 27 subjects originally randomized to the treatment and control groups. The treatment group lost 8.4% +/- 5.6% of body weight, whereas weight did not change in the control group (+0.5% +/- 2.8%; P<.001). Compared with the control group, fat mass decreased (-6.6 +/- 3.4 vs +1.7 +/- 4.1 kg; P<.001), without a change in fat-free mass (-1.2 +/- 2.1 vs -1.0 +/- 3.5 kg; P = .75) in the treatment group. The Physical Performance Test score (2.6 +/- 2.5 vs 0.1 +/- 1.0; P = .001), peak oxygen consumption (1.7 +/- 1.6 vs 0.3 +/- 1.1 mL/min per kilogram; P = .02), and Functional Status Questionnaire score (2.9 +/- 3.7 vs -0.2 +/- 3.9; P = .02) improved in treated subjects compared with control subjects. Treatment also improved strength, walking speed, obstacle course, 1-leg limb stance time, and health survey physical subscale scores (all P<.05).
Conclusion:
These findings suggest that weight loss and exercise can ameliorate frailty in obese older adults. Trial Registration clinicaltrials.gov Identifier: NCT00146133.
Increasing evidence supports carbohydrate restricted diets (CRD) for weight loss and improvement in traditional markers for cardiovascular disease (CVD); less is known regarding emerging CVD risk factors. We previously reported that a weight loss intervention based on a CRD (% carbohydrate:fat:protein = 13:60:27) led to a mean weight loss of 7.5 kg and a 20% reduction of abdominal fat in 29 overweight men. This group showed reduction in plasma LDL-cholesterol and triglycerides and elevations in HDL-cholesterol as well as reductions in large and medium VLDL particles and increases in LDL particle size. In this study we report on the effect of this intervention with and without fiber supplementation on plasma homocysteine, lipoprotein (a) [Lp(a)], C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha).
Twenty nine overweight men [body mass index (BMI) 25-35 kg/m2] aged 20-69 years consumed an ad libitum CRD (% carbohydrate:fat:protein = 13:60:27) including a standard multivitamin every other day for 12 wk. Subjects were matched by age and BMI and randomly assigned to consume 3 g/d of either a soluble fiber supplement (n = 14) or placebo (n = 15).
There were no group or interaction (fiber x time) main effects, but significant time effects were observed for several variables. Energy intake was spontaneously reduced (-30.5%). This was accompanied by an increase in protein intake (96.2 +/- 29.8 g/d to 107.3 +/- 29.7 g/d) and methionine intake (2.25 +/- 0.7 g/d, to 2.71 +/- 0.78 g/d; P < 0.001). Trans fatty acid intake was significantly reduced (-38.6%) while dietary folate was unchanged, as was plasma homocysteine. Bodyweight (-7.5 +/- 2.5 kg) was reduced as was plasma Lp(a) (-11.3%). Changes in plasma Lp(a) correlated with reductions in LDL-cholesterol (r = .436, P < 0.05) and fat loss (r = .385, P < 0,05). At wk 12, both CRP (-8.1%) and TNF-alpha (-9.3%) were reduced (P < 0.05) independently of weight loss. IL-6 concentrations were unchanged.
A diet based on restricting carbohydrates leads to spontaneous caloric reduction and subsequent improvement in emerging markers of CVD in overweight/obese men who are otherwise healthy.
The loss of muscle mass is considered to be a major determinant of strength loss in aging. However, large-scale longitudinal studies examining the association between the loss of mass and strength in older adults are lacking.
Three-year changes in muscle mass and strength were determined in 1880 older adults in the Health, Aging and Body Composition Study. Knee extensor strength was measured by isokinetic dynamometry. Whole body and appendicular lean and fat mass were assessed by dual-energy x-ray absorptiometry and computed tomography.
Both men and women lost strength, with men losing almost twice as much strength as women. Blacks lost about 28% more strength than did whites. Annualized rates of leg strength decline (3.4% in white men, 4.1% in black men, 2.6% in white women, and 3.0% in black women) were about three times greater than the rates of loss of leg lean mass ( approximately 1% per year). The loss of lean mass, as well as higher baseline strength, lower baseline leg lean mass, and older age, was independently associated with strength decline in both men and women. However, gain of lean mass was not accompanied by strength maintenance or gain (ss coefficients; men, -0.48 +/- 4.61, p =.92, women, -1.68 +/- 3.57, p =.64).
Although the loss of muscle mass is associated with the decline in strength in older adults, this strength decline is much more rapid than the concomitant loss of muscle mass, suggesting a decline in muscle quality. Moreover, maintaining or gaining muscle mass does not prevent aging-associated declines in muscle strength.
Context:
Popular diets, particularly those low in carbohydrates, have challenged current recommendations advising a low-fat, high-carbohydrate diet for weight loss. Potential benefits and risks have not been tested adequately.
Objective:
To compare 4 weight-loss diets representing a spectrum of low to high carbohydrate intake for effects on weight loss and related metabolic variables.
Design, setting, and participants:
Twelve-month randomized trial conducted in the United States from February 2003 to October 2005 among 311 free-living, overweight/obese (body mass index, 27-40) nondiabetic, premenopausal women.
Intervention:
Participants were randomly assigned to follow the Atkins (n = 77), Zone (n = 79), LEARN (n = 79), or Ornish (n = 76) diets and received weekly instruction for 2 months, then an additional 10-month follow-up.
Main outcome measures:
Weight loss at 12 months was the primary outcome. Secondary outcomes included lipid profile (low-density lipoprotein, high-density lipoprotein, and non-high-density lipoprotein cholesterol, and triglyceride levels), percentage of body fat, waist-hip ratio, fasting insulin and glucose levels, and blood pressure. Outcomes were assessed at months 0, 2, 6, and 12. The Tukey studentized range test was used to adjust for multiple testing.
Results:
Weight loss was greater for women in the Atkins diet group compared with the other diet groups at 12 months, and mean 12-month weight loss was significantly different between the Atkins and Zone diets (P<.05). Mean 12-month weight loss was as follows: Atkins, -4.7 kg (95% confidence interval [CI], -6.3 to -3.1 kg), Zone, -1.6 kg (95% CI, -2.8 to -0.4 kg), LEARN, -2.6 kg (-3.8 to -1.3 kg), and Ornish, -2.2 kg (-3.6 to -0.8 kg). Weight loss was not statistically different among the Zone, LEARN, and Ornish groups. At 12 months, secondary outcomes for the Atkins group were comparable with or more favorable than the other diet groups.
Conclusions:
In this study, premenopausal overweight and obese women assigned to follow the Atkins diet, which had the lowest carbohydrate intake, lost more weight at 12 months than women assigned to follow the Zone diet, and had experienced comparable or more favorable metabolic effects than those assigned to the Zone, Ornish, or LEARN diets [corrected] While questions remain about long-term effects and mechanisms, a low-carbohydrate, high-protein, high-fat diet may be considered a feasible alternative recommendation for weight loss.
Trial registration:
clinicaltrials.gov Identifier: NCT00079573.
We examined the hypothesis that insulin resistance in skeletal muscle promotes the development of atherogenic dyslipidemia, associated with the metabolic syndrome, by altering the distribution pattern of postprandial energy storage. Following ingestion of two high carbohydrate mixed meals, net muscle glycogen synthesis was reduced by ≈60% in young, lean, insulin-resistant subjects compared with a similar cohort of age–weight–body mass index–activity-matched, insulin-sensitive, control subjects. In contrast, hepatic de novo lipogenesis and hepatic triglyceride synthesis were both increased by >2-fold in the insulin-resistant subjects. These changes were associated with a 60% increase in plasma triglyceride concentrations and an ≈20% reduction in plasma high-density lipoprotein concentrations but no differences in plasma concentrations of TNF-α, IL-6, adiponectin, resistin, retinol binding protein-4, or intraabdominal fat volume. These data demonstrate that insulin resistance in skeletal muscle, due to decreased muscle glycogen synthesis, can promote atherogenic dyslipidemia by changing the pattern of ingested carbohydrate away from skeletal muscle glycogen synthesis into hepatic de novo lipogenesis, resulting in an increase in plasma triglyceride concentrations and a reduction in plasma high-density lipoprotein concentrations. Furthermore, insulin resistance in these subjects was independent of changes in the plasma concentrations of TNF-α, IL-6, high-molecular-weight adiponectin, resistin, retinol binding protein-4, or intraabdominal obesity, suggesting that these factors do not play a primary role in causing insulin resistance in the early stages of the metabolic syndrome.
• type 2 diabetes
• nonalcoholic fatty liver disease
• adipocytokines
• abdominal obesity
• atherogenic dyslipidemia
Obesity causes serious medical complications and impairs quality of life. Moreover, in older persons, obesity can exacerbate the age-related decline in physical function and lead to frailty. However, appropriate treatment for obesity in older persons is controversial because of the reduction in relative health risks associated with increasing body mass index and the concern that weight loss could have potential harmful effects in the older population. This joint position statement from the American Society for Nutrition and the NAASO, The Obesity Society reviews the clinical issues related to obesity in older persons and provides health professionals with appropriate weight-management guidelines for obese older patients. The current data show that weight-loss therapy improves physical function, quality of life, and the medical complications associated with obesity in older persons. Therefore, weight-loss therapy that minimizes muscle and bone losses is recommended for older persons who are obese and who have functional impairments or medical complications that can benefit from weight loss.
The National Cholesterol Education Program’s Adult Treatment Panel III report (ATP III)1 identified the metabolic syndrome as a multiplex risk factor for cardiovascular disease (CVD) that is deserving of more clinical attention. The cardiovascular community has responded with heightened awareness and interest. ATP III criteria for metabolic syndrome differ somewhat from those of other organizations. Consequently, the National Heart, Lung, and Blood Institute, in collaboration with the American Heart Association, convened a conference to examine scientific issues related to definition of the metabolic syndrome. The scientific evidence related to definition was reviewed and considered from several perspectives: (1) major clinical outcomes, (2) metabolic components, (3) pathogenesis, (4) clinical criteria for diagnosis, (5) risk for clinical outcomes, and (6) therapeutic interventions.
ATP III viewed CVD as the primary clinical outcome of metabolic syndrome. Most individuals who develop CVD have multiple risk factors. In 1988, Reaven2 noted that several risk factors (eg, dyslipidemia, hypertension, hyperglycemia) commonly cluster together. This clustering he called Syndrome X , and he recognized it as a multiplex risk factor for CVD. Reaven and subsequently others postulated that insulin resistance underlies Syndrome X (hence the commonly used term insulin resistance syndrome ). Other researchers use the term metabolic syndrome for this clustering of metabolic risk factors. ATP III used this alternative term. It avoids the implication that insulin resistance is the primary or only cause of associated risk factors. Although ATP III identified CVD as the primary clinical outcome of the metabolic syndrome, most people with this syndrome have insulin resistance, which confers increased risk for type 2 diabetes. When diabetes becomes clinically apparent, CVD risk rises sharply. Beyond CVD and type 2 diabetes, individuals with metabolic syndrome seemingly are susceptible to other conditions, notably polycystic ovary syndrome, fatty liver, cholesterol gallstones, asthma, sleep disturbances, and some …
Following glucose ingestion, tissue glucose uptake is enhanced and endogenous glucose production is inhibited, thus contributing to the maintenance of normal glucose tolerance. To examine whether these responses are disturbed in diabetes, glucose kinetics after oral glucose administration were studied in 12 non-insulin-dependent diabetic and 10 age- and weight-matched control subjects. A double tracer approach was used, whereby the endogenous glucose pool was labeled with 3-3H-glucose and the oral load with 1-14C-glucose. The two glucose tracers were separated in plasma by a two-step chromatographic procedure, and the two sets of isotopic data were analyzed according to a two-compartment model for the glucose system. Basally, glucose production was slightly higher in diabetics than in controls (2.51 +/- 0.24 v 2.28 +/- 0.11 mg/kg.min, NS) even though the former had higher plasma glucose (189 +/- 19 v 93 +/- 2 mg/dL, P less than .001) and insulin (23 +/- 4 v 12 +/- 1 microU/mL, P less than .05) concentrations. Following the ingestion of 1 g/kg of glucose, oral glucose appeared in the peripheral circulation in similar time-course and amount in the two groups (75 +/- 2% of the load over 3.5 hours in the diabetics v 76 +/- 3% in controls). Endogenous glucose production was promptly inhibited in diabetic and normal subjects alike, but the mean residual hepatic glucose production after glucose ingestion was significantly greater in the diabetic group (17 +/- 2 v 10 +/- 3 g/3.5 h, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)
A method for estimating the cholesterol content of the serum low-density lipoprotein fraction (Sf- 0.20)is presented. The method involves measure- ments of fasting plasma total cholesterol, tri- glyceride, and high-density lipoprotein cholesterol concentrations, none of which requires the use of the preparative ultracentrifuge. Cornparison of this suggested procedure with the more direct procedure, in which the ultracentrifuge is used, yielded correlation coefficients of .94 to .99, de- pending on the patient population compared. Additional Keyph rases hyperlipoproteinemia classifi- cation #{149} determination of plasma total cholesterol, tri- glyceride, high-density lipoprotein cholesterol #{149} beta lipo proteins
Twenty-four obese but otherwise normal men and women were followed for: Two weeks on their usual food intake; eight weeks on a high-protein, low-carbohydrate diet; and then again for two weeks on their usual diet. During this time, several metabolic parameters were measured bimonthly. The high-protein, low-carbohydrate dieting resulted in substantial weight loss, probably due to a combination of salt and water loss, as well as caloric restriction. Plasma triglycerides fell as well. Significant increases occurred in LDL-cholesterol, uric acid, and free fatty acid levels. HDL-cholesterol levels failed to rise despite significant weight loss, indicating that the previously reported relationship between HDL-cholesterol and weight may be dependent, in part, on the composition of the diet.
The purpose of the study was to examine the associations of physical capacity, as determined on the basis of self-report and physical measurements, with survival in three groups of elderly people aged 75, 80 and 75–84 years. The main aspects of physical capacity were mobility, walking speed, hand grip strength and knee extension strength. Altogether 1142 persons participated in the mobility interview, of whom 466 also took part in the walking speed test, and 463 in the strength tests. The follow-up periods ranged from 48 to 58 months.
Risk of death was significantly related to difficulties in indoor mobility among the 75–84-year-olds (odds ratio = 1.99, 95% confidence interval = 1.27–3.13) and 75- and 80-year-olds (OR = 1.60, CI = 1.07−2.38) and outdoor mobility among the 75–84-year-olds (OR = 2.44, CI = 1.63−3.67) and 75- and 80-year-olds (OR = 2.75, CI = 1.72–4.40). The odds ratios for hand grip strength (OR = 1.86, CI = 1.13−3.07), knee extension strength (OR = 2.52, CI = 1.50−4.42) and walking time over 10 metres (OR = 1.98, CI = 1.18−3.34) for the 75- and 80-year-olds were also significant. Since these variables can be easily measured and provide valuable information about functional capacity and risk of death they merit inclusion in medical examinations of elderly clients.
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.
The National Cholesterol Education Program’s Adult Treatment Panel III report (ATP III)1 identified the metabolic syndrome as a multiplex risk factor for cardiovascular disease (CVD) that is deserving of more clinical attention. The cardiovascular community has responded with heightened awareness and interest. ATP III criteria for metabolic syndrome differ somewhat from those of other organizations. Consequently, the National Heart, Lung, and Blood Institute, in collaboration with the American Heart Association, convened a conference to examine scientific issues related to definition of the metabolic syndrome. The scientific evidence related to definition was reviewed and considered from several perspectives: (1) major clinical outcomes, (2) metabolic components, (3) pathogenesis, (4) clinical criteria for diagnosis, (5) risk for clinical outcomes, and (6) therapeutic interventions.
ATP III viewed CVD as the primary clinical outcome of metabolic syndrome. Most individuals who develop CVD have multiple risk factors. In 1988, Reaven2 noted that several risk factors (eg, dyslipidemia, hypertension, hyperglycemia) commonly cluster together. This clustering he called Syndrome X , and he recognized it as a multiplex risk factor for CVD. Reaven and subsequently others postulated that insulin resistance underlies Syndrome X (hence the commonly used term insulin resistance syndrome ). Other researchers use the term metabolic syndrome for this clustering of metabolic risk factors. ATP III used this alternative term. It avoids the implication that insulin resistance is the primary or only cause of associated risk factors. Although ATP III identified CVD as the primary clinical outcome of the metabolic syndrome, most people with this syndrome have insulin resistance, which confers increased risk for type 2 diabetes. When diabetes becomes clinically apparent, CVD risk rises sharply. Beyond CVD and type 2 diabetes, individuals with metabolic syndrome seemingly are susceptible to other conditions, notably polycystic ovary syndrome, fatty liver, cholesterol gallstones, asthma, sleep disturbances, and some …
Bioimpedance analysis (BIA) is a potential field and clinical method for evaluating skeletal muscle mass (SM) and %fat. A new BIA system has 8-(two on each hand and foot) rather than 4-contact electrodes allowing for rapid 'whole-body' and regional body composition evaluation.
This study evaluated the 50 kHz BC-418 8-contact electrode and TBF-310 4-contact electrode foot-foot BIA systems (Tanita Corp., Tokyo, Japan).
There were 40 subject evaluations in males (n=20) and females (n=20) ranging in age from 6 to 64 y. BIA was evaluated in each subject and compared to reference lean soft-tissue (LST) and %fat estimates in the appendages and remainder (trunk+head) provided by dual-energy X-ray absorptiometry (DXA). Appendicular LST (ALST) estimates from both BIA and DXA were used to derive total body SM mass.
The highest correlation between total body LST by DXA and impedance index (Ht(2)/Z) by BC-418 was for the foot-hand segments (r=0.986; left side only) compared to the arm (r=0.970-0.979) and leg segments (r=0.942-0.957)(all P<0.001). The within- and between-day coefficient of variation for %fat and ALST evaluated in five subjects was <1% and approximately 1-3.7%, respectively. The correlations between 8-electrode predicted and DXA appendicular (arms, legs, total) and trunk+head LST were strong and highly significant (all r> or =0.95, P<0.001) and group means did not differ across methods. Skeletal muscle mass calculated (Kim equation) from total ALST by DXA (X+/-s.d.)(23.7+/-9.7 kg) was not significantly different and highly correlated with BC-418 estimates (25.2+/-9.6 kg; r=0.96, P<0.001). There was a good correlation between total body %fat by 8-electrode BIA vs DXA (r=0.87, P<0.001) that exceeded the corresponding association with 4-electrode BIA (r=0.82, P<0.001). Group mean segmental %fat estimates from BC-418 did not differ significantly from corresponding DXA estimates. No between-method bias was detected in the whole body, ALST, and skeletal muscle analyses.
The new 8-electrode BIA system offers an important new opportunity of evaluating SM in research and clinical settings. The additional electrodes of the new BIA system also improve the association with DXA %fat estimates over those provided by the conventional foot-foot BIA.
three major strategies have been tested for combating the losses in muscle mass and strength that accompany ageing. Those strategies are testosterone replacement for men, growth hormone replacement and resistance exercise training. This review will cover the risks and benefits associated with each of these interventions.
searches of PubMed and Web of Science through May 2004 yielded 85 relevant citations for the following descriptors: sarcopenia, aging/ageing, elderly, testosterone, hormone replacement, growth hormone, resistance training, exercise, muscle mass, nutrition and strength.
testosterone replacement in elderly hypogonadal men produces only modest increases in muscle mass and strength, which are observed in some studies and not in others. Higher doses have not been given for fear of accelerating prostate cancer. Growth hormone replacement in elderly subjects produces a high incidence of side-effects, does not increase strength and does not augment strength gains resulting from resistance training. Some alternate strategies for stimulating the growth hormone/insulin-like growth factor (IGF) pathway continue to hold promise. The latter include growth hormone releasing hormone (GHRH) and the complex of IGF-I with its major circulating binding protein (IGF-I/IGFBP-3). Resistance training remains the most effective intervention for increasing muscle mass and strength in older people. Elderly people have reduced food intake and increased protein requirements. As a result, adequate nutrition is sometimes a barrier to obtaining full benefits from resistance training in this population.
The associations between macronutrient intake and plasma parameters associated with increased risk for coronary heart disease (CHD) were evaluated in 80 overweight premenopausal women. We hypothesized that higher carbohydrate intake would be associated with a more detrimental plasma lipid profile. Dietary data were collected using a validated food frequency questionnaire (FFQ). Plasma total cholesterol (TC), triglycerides (TGs), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were determined from two fasting blood samples. In addition, selected apolipoproteins (apo) and LDL peak size were measured. Values for TC, TG and HDL were not in the range of risk classification; however, the mean values of LDL-C, 2.7 +/- 0.7 mmol/L, were higher than the current recommendations. Carbohydrate intake was positively associated with TG and apo C-III (P < .01) concentrations, and negatively associated with LDL diameter (P < .01). Participants were divided into low (<53% of energy) or high (> or = 53% energy) carbohydrate intake groups. Individuals in the <53% carbohydrate group consumed more cholesterol and total fat, but also had higher intake of polyunsaturated and monounsaturated fatty acids (SFAs). In contrast, subjects in the > or =53% group consumed higher concentrations of glucose and fructose than those in the low-carbohydrate (LC) group. In addition, subjects consuming <53% carbohydrate had lower concentrations of LDL-C and apo B (P < .01) and a larger LDL diameter (P < .05) than the > or =53% group. These results suggest that the lower LDL-C in the LC group may be related to both the amount of carbohydrate and the type of fatty acids consumed by these subjects.
Obesity causes serious medical complications and impairs quality of life. Moreover, in older persons, obesity can exacerbate the age-related decline in physical function and lead to frailty. However, appropriate treatment for obesity in older persons is controversial because of the reduction in relative health risks associated with increasing body mass index and the concern that weight loss could have potential harmful effects in the older population. This joint position statement from the American Society for Nutrition and NAASO, The Obesity Society reviews the clinical issues related to obesity in older persons and provides health professionals with appropriate weight-management guidelines for obese older patients. The current data show that weight-loss therapy improves physical function, quality of life, and the medical complications associated with obesity in older persons. Therefore, weight-loss therapy that minimizes muscle and bone losses is recommended for older persons who are obese and who have functional impairments or medical complications that can benefit from weight loss.
Recently, diets low in carbohydrate content have become a matter of international attention because of the WHO recommendations to reduce the overall consumption of sugars and rapidly digestible starches. One of the common metabolic changes assumed to take place when a person follows a low-carbohydrate diet is ketosis. Low-carbohydrate intakes result in a reduction of the circulating insulin level, which promotes high level of circulating fatty acids, used for oxidation and production of ketone bodies. It is assumed that when carbohydrate availability is reduced in short term to a significant amount, the body will be stimulated to maximize fat oxidation for energy needs. The currently available scientific literature shows that low-carbohydrate diets acutely induce a number of favourable effects, such as a rapid weight loss, decrease of fasting glucose and insulin levels, reduction of circulating triglyceride levels and improvement of blood pressure. On the other hand some less desirable immediate effects such as enhanced lean body mass loss, increased urinary calcium loss, increased plasma homocysteine levels, increased low-density lipoprotein-cholesterol have been reported. The long-term effect of the combination of these changes is at present not known. The role of prolonged elevated fat consumption along with low-carbohydrate diets should be addressed. However, these undesirable effects may be counteracted with consumption of a low-carbohydrate, high-protein, low-fat diet, because this type of diet has been shown to induce favourable effects on feelings of satiety and hunger, help preserve lean body mass, effectively reduce fat mass and beneficially impact on insulin sensitivity and on blood lipid status while supplying sufficient calcium for bone mass maintenance. The latter findings support the need to do more research on this type of hypocaloric low-carbohydrate diet.
This article, which is partly biographical and partly scientific, summarizes a life in academic medicine. It relates my progress from benchside to bedside and then to academic and research administration, and concludes with the teaching of human biology to college undergraduates. My experience as an intern (anno 1953) treating a youngster in diabetic ketoacidosis underscored our ignorance of the controls in human fuel metabolism. Circulating free fatty acids were then unknown, insulin could not be measured in biologic fluids, and beta-hydroxybutyric acid, which was difficult to measure, was considered by many a metabolic poison. The central role of insulin and the metabolism of free fatty acids, glycerol, glucose, lactate, and pyruvate, combined with indirect calorimetry, needed characterization in a near-steady state, namely prolonged starvation. This is the main topic of this chapter. Due to its use by brain, D-beta-hydroxybutyric acid not only has permitted man to survive prolonged starvation, but also may have therapeutic potential owing to its greater efficiency in providing cellular energy in ischemic states such as stroke, myocardial insufficiency, neonatal stress, genetic mitochondrial problems, and physical fatigue.
The purpose of this study was to quantify the decrease in the load lifted from 1 to 5, 10, and 20 repetitions to failure for the flat barbell bench press (chest press; CP) and plate-loaded leg press (LP). Furthermore, we developed prediction equations for 1 repetition maximum (RM) strength from the multiple RM tests, including anthropometric data, gender, age, and resistance training volume. Seventy subjects (34 men, 36 women), 18-69 years of age, completed 1, 5, 10, and 20RM testing for each of the CPs and LPs. Regression analyses of mean data revealed a nonlinear decrease in load with increasing repetition number (CP: linear S(y.x) = 2.6 kg, nonlinear S(y.x) = 0.2 kg; LP: linear S(y.x) = 11.0 kg, nonlinear S(y.x) = 2.6 kg, respectively). Multiple regression analyses revealed that the 5RM data produced the greatest prediction accuracy, with R(2) data for 5, 10, and 20RM conditions being LP: 0.974, 0.933, 0.915; CP: 0.993, 0.976, and 0.955, respectively. The regression prediction equations for 1RM strength from 5RM data were LP: 1RM = 1.0970 x (5RM weight [kg]) + 14.2546, S(y.x) = 16.16 kg, R(2) = 0.974; CP: 1RM = 1.1307 x (5RM weight) + 0.6999, S(y.x) = 2.98 kg, R(2) = 0.993. Dynamic muscular strength (1RM) can be accurately estimated from multiple repetition testing. Data reveal that no more than 10 repetitions should be used in linear equations to estimate 1RM for the LP and CP actions.
To evaluate the effect of adding exercise to a hypocaloric diet on changes in appendicular lean mass and strength in frail obese older adults undergoing voluntary weight loss.
Thirty frail older (age, 70 +/- 5 yr) obese (body mass index, 37 +/- 5 kg.m) adults were randomly assigned to 6 months of diet/behavioral therapy (diet group, n = 15) or diet or behavioral therapy plus exercise that incorporated progressive resistance training (PRT; diet + exercise group; n = 15). Body composition was assessed using dual-energy x-ray absorptiometry, and muscle strength was assessed using one-repetition maximum. The volume of upper extremity (UE) and lower extremity (LE) exercise training was determined by multiplying the average number of repetitions performed by the average weight lifted during the first three exercise sessions and during the last three exercise sessions of the study.
The diet and the diet + exercise groups had similar (P > 0.05) decreases in weight (10.7 +/- 4.5 vs 9.7 +/- 4.0 kg) and fat mass (6.8 +/- 3.7 vs 7.7 +/- 2.9 kg). However, the diet + exercise group lost less fat-free mass (FFM; 1.8 +/- 1.5 vs 3.5 +/- 2.1 kg), LE lean mass (0.9 +/- 0.8 vs 2.0 +/- 0.9 kg), and UE lean mass (0.1 +/- 0.2 vs 0.2 +/- 0.2 kg) than the diet group (P < 0.05). The diet + exercise group had greater increases in percent of weight as FFM (FFM / weight x 100) than the diet group (7.9 +/- 3.3 vs 5.4 +/- 3.7%; P < 0.05). Despite lean mass losses, the diet + exercise group increased UE and LE strength in response to exercise (17-43%), whereas the diet group maintained strength. The volume of UE and LE exercises correlated with the amount of UE and LE lean mass (r = 0.64-0.84; P < 0.05).
Exercise added to diet reduces muscle mass loss during voluntary weight loss and increases muscle strength in frail obese older adults. Regular exercise that incorporates PRT should be used to attenuate muscle mass loss in frail obese older adults on weight-loss therapy.
ATC, CSCS Department of Exercise Science & Sport Studies Springfield College 263 Alden Street Springfield, MA 01109 E-mail: rwood@spfldcol
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Address correspondence to: Richard J. Wood, Ph.D., ATC, CSCS Department of Exercise Science & Sport Studies Springfield College 263 Alden Street Springfield, MA 01109 E-mail: rwood@spfldcol.edu