Effects of consuming a high-protein diet with or without soy protein during weight loss and maintenance: a non-inferiority, randomized clinical efficacy trial.

OBJECTIVE: This 12-month randomized, non-inferiority clinical trial sought to determine the impact of consuming soy protein as part of an energy-restricted, high-protein diet on weight loss, body composition and cardiometabolic health. METHODS: Seventy-one adults (58 female) with overweight or obesity (body mass index: 32.9 ± 3.6 kg m-2) were randomly assigned to consume three servings of soy (S) or non-soy (NS) protein foods per day for 12 months. All participants completed a group-based behavioural weight loss program lasting 4 months (M4), and follow-up assessments were completed at month 12 (M12). RESULTS: Body weight was reduced in both groups at M4 (S: -7.0% ± 5.2%, NS: -7.1% ± 5.7%) and M12 (S: 3.6% ± 5.1%, NS: -4.8% ± 7.3%). Body weight reductions (mean difference [90% confidence interval]) were not different between S and NS at either time point (M4: -0.16% [-1.4, 3.6], P = 0.90; M12: 1.1% [-1.4, 3.6], P = 0.44). Differences in body fat mass loss were not different between S and NS at M4 (0.29 ± 0.84 kg, P = 0.73) or M12 (0.78 ± 1.5 kg, P = 0.59). Weight loss-induced improvements in cholesterol, triglycerides and blood pressure did not differ between S and NS. CONCLUSION: These results indicate that soy-based protein foods can be effectively incorporated into an energy-restricted, high-protein diet for improving body weight, body composition and cardiometabolic health.

Is regular exercise an effective strategy for weight loss maintenance?

Weight regain after weight loss is one of the most significant challenges to successful obesity treatment. Regular exercise has long been touted as a strategy for weight loss maintenance, but the lack of clear evidence in clinical trials has caused some to question its effectiveness. In this review, we present the arguments both questioning and in support of exercise as an obesity therapeutic. Our purpose is to bring clarity to the literature, present a unified perspective, and identify the gaps in knowledge that need to be addressed in future studies. Critical questions remain including sex differences, individual variability and compensatory behaviors in response to exercise, exercise adherence, the role of energy flux and the molecular mechanisms mediating the beneficial effects of exercise after weight loss and during weight regain. Future research should focus on these critical questions to provide a more complete understanding of the potential benefits of exercise on weight loss maintenance.

Equivalent reductions in body weight during the Beef WISE Study: beef's role in weight improvement, satisfaction and energy.

OBJECTIVE: The objective of this randomized equivalence trial was to determine the impact of consuming lean beef as part of a high protein (HP) weight-reducing diet on changes in body weight, body composition and cardiometabolic health. METHODS: A total of 120 adults (99 female) with overweight or obesity (BMI: 35.7 ± 7.0 kg m-2) were randomly assigned to consume either a HP diet with ≥4 weekly servings of lean beef (B; n = 60) or a HP diet restricted in all red meats (NB; n = 60) during a 16-week weight loss intervention. RESULTS: Body weight was reduced by 7.8 ± 5.9% in B and 7.7 ± 5.5% in NB (p < 0.01 for both). Changes in percent body weight were equivalent between B and NB (mean difference: 0.06%, 90% confidence interval: (-1.7, 1.8)). Fat mass was reduced in both groups (p < 0.01; B: 8.0 ± 0.6 kg, NB: 8.6 ± 0.6 kg), while lean mass was not reduced in either group. Improvements in markers of cardiometabolic health (total cholesterol, low-density lipoprotein cholesterol, triglycerides and blood pressure) were not different between B and NB. CONCLUSION: Results of this study demonstrate that HP diets - either rich or restricted in red meat intakes - are effective for decreasing body weight and improving body composition and cardiometabolic health.

The association between obesity and academic performance in youth: a systematic review.

Previous studies have found that obesity could influence academic performance. The aim of this study was to systematically review the scientific evidence on the association between obesity and academic performance in school children. A systematic review of English articles was undertaken by using databases PubMed/Medline, ERIC, LILACS, SciELO and Web of Science. Cross-sectional and longitudinal studies examining the association between obesity and academic performance in children and adolescents, published between January 1990 and December 2016, were included. Risk of bias was assessed by using Strengthening the Reporting of Observational Studies in Epidemiology. Thirty-four studies (23 cross-sectional and 11 longitudinal) matched all inclusion criteria and were included. Seven studies were classified as low risk of bias, 23 as medium risk and four as high risk. After controlling for covariates such as socio-economic status, parental education and physical activity, the association between obesity and academic performance becomes uncertain for most of the studies (55.9%). Therefore, at present, there is insufficient evidence to support a direct link between obesity and poor academic performance in school age children. In order to clarify this issue, we need more longitudinal studies with adequate sample sizes and that control for potential confounders.

Physical fitness and academic performance in youth: A systematic review.

Physical fitness (PF) is a construct of health- and skill-related attributes which have been associated with academic performance (AP) in youth. This study aimed to review the scientific evidence on the association among components of PF and AP in children and adolescents. A systematic review of articles using databases PubMed/Medline, ERIC, LILACS, SciELO, and Web of Science was undertaken. Cross-sectional and longitudinal studies examining the association between at least one component of PF and AP in children and adolescents, published between 1990 and June 2016, were included. Independent extraction of articles was carried out by the two authors using predefined data fields. From a total of 45 studies included, 25 report a positive association between components of PF with AP and 20 describe a single association between cardiorespiratory fitness (CRF) and AP. According to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines: 12 were classified as low, 32 as medium risk, and 1 as high risk of bias. Thirty-one studies reported a positive association between AP and CRF, six studies with muscular strength, three studies with flexibility, and seven studies reported a positive association between clustered of PF components and AP. The magnitude of the associations is weak to moderate (ß = 0.10-0.42 and odds = 1.01-4.14). There is strong evidence for a positive association between CRF and cluster of PF with AP in cross-sectional studies; and evidence from longitudinal studies for a positive association between cluster of PF and AP; the relationship between muscular strength and flexibility with AP remains uncertain.

The association of change in physical activity and body weight in the regulation of total energy expenditure.

BACKGROUND/OBJECTIVES: The limited success in addressing the current obesity epidemic reflects the insufficient understanding of the regulation of energy balance. The present study examines the longitudinal association of body weight with physical activity (PA), total daily energy expenditure (TDEE) and total daily energy intake (TDEI). SUBJECTS/METHODS: A total of 195 adults (52% male) between 21 and 35 years of age with no intention for weight loss were followed over a 2-year period. Body weight, fat mass and fat-free mass were measured every 3 months. Participants were stratified into three groups based on change in body weight using a 5% cutpoint. TDEE and time spent in different PA intensities were determined via a multisensor device at each measurement time. TDEI was calculated based on change in body composition and TDEE. RESULTS: At 2-year follow-up, 57% of the participants maintained weight, 14% lost weight and 29% gained weight. Average weight change was -6.9±3.4 and 7.1±3.6 kg in the weight-loss and weight-gain groups, respectively. Average TDEE and TDEI did not change significantly in any weight change group (P>0.16). Moderate-to-vigorous PA, however, increased significantly in the weight-loss group (35±49 min/day; P<0.01) and decreased in the weight-gain group (-35±46 min/day; P<0.01). CONCLUSIONS: Results of this observational study indicate an inverse association between body weight and PA to maintain a stable TDEE and allow for a stable TDEI over time. Sufficient PA levels, therefore, are an important contributor to weight loss maintenance.

Initial weight loss goals: have they changed and do they matter?

OBJECTIVE: Nearly 20 years ago, participants in behavioural weight loss programmes reported goals that greatly exceeded the amount of weight typically produced by these programmes. Whether having unrealistic weight loss goals impacts weight loss or attrition is unclear. The intent of the current study was to revisit current weight loss goals and examine whether goals impact outcomes. METHODS: Adults (N = 308, BMI = 33.7 ± 4.2 kg/m2) participated in a 12-month behavioural weight management programme and completed questionnaires about their goals. RESULTS: Participants' weight loss goal was 19.8 ± 7.9% of their body weight, and 90.4% selected a goal ≥10%. Weight goals were not associated with weight loss at 3 (p = 0.75) or 12 months (p = 0.47), or from 3 to 12 months (p = 0.55). Weight loss goals were not related to attrition at 3 (p = 0.91) or 12 months (p = 0.86). Participants believed that weight reduction would positively impact their health and psychosocial functioning. CONCLUSION: Weight loss goals have decreased, but still greatly exceed what can be expected by most. Unrealistic goals, however, had no impact on weight loss or attrition. These results question the utility of counseling people with obesity to set more realistic weight loss goals, which is typically practiced in behavioural weight management.

The effects of experimentally manipulated social status on acute eating behavior: A randomized, crossover pilot study.

Both subjective and objectively measured social status has been associated with multiple health outcomes, including weight status, but the mechanism for this relationship remains unclear. Experimental studies may help identify the causal mechanisms underlying low social standing as a pathway for obesity. Our objective was to investigate the effects of experimentally manipulated social status on ad libitum acute dietary intakes and stress-related outcomes as potential mechanisms relating social status and weight. This was a pilot feasibility, randomized, crossover study in Hispanic young adults (n=9; age 19-25; 67% female; BMI ≥18.5 and ≤30kg/m(2)). At visit 1, participants consumed a standardized breakfast and were randomized to a high social status position (HIGH) or low social status position (LOW) in a rigged game of Monopoly™. The rules for the game differed substantially in terms of degree of 'privilege' depending on randomization to HIGH or LOW. Following Monopoly™, participants were given an ad libitum buffet meal and energy intakes (kcal) were estimated by pre- and post-weighing foods consumed. Stress-related markers were measured at baseline, after the game of Monopoly™, and after lunch. Visit 2 used the same standardized protocol; however, participants were exposed to the opposite social status condition. When compared to HIGH, participants in LOW consumed 130 more calories (p=0.07) and a significantly higher proportion of their daily calorie needs in the ad libitum buffet meal (39% in LOW versus 31% in HIGH; p=0.04). In LOW, participants reported decreased feelings of pride and powerfulness following Monopoly™ (p=0.05) and after their lunch meal (p=0.08). Relative to HIGH, participants in LOW demonstrated higher heart rates following Monopoly™ (p=0.06), but this relationship was not significant once lunch was consumed (p=0.31). Our pilot data suggest a possible causal relationship between experimentally manipulated low social status and increased acute energy intakes in Hispanic young adults, potentially influenced by decreased feelings of pride and powerfulness. Increased energy intake over time, resulting in positive energy balance, could contribute to increased risk for obesity, which could partially explain the observed relationship between low social standing and higher weight. Larger and longitudinal studies in a diverse sample need to be conducted to confirm findings, increase generalizability, and assess whether this relationship persists over time.

Does exercise intensity affect blood pressure and heart rate in obese adolescents? A 6-month multidisciplinary randomized intervention study.

BACKGROUND: Aerobic exercise improves cardiovascular health in general, but whether the impact varies with exercise intensity is not clear. OBJECTIVE: The aim of the current study was to compare the effects of a high-intensity aerobic exercise training (HIT) vs. a low-intensity aerobic exercise training (LIT) on blood pressure (BP), heart rate (HR) and heart rate variability (HRV) in obese adolescents. METHODS: Forty-three (13-18 years) Tanner stage (III-IV) matched obese adolescents were studied in a randomized trial of either HIT (corresponding to the ventilatory threshold I; n = 20) or LIT (corresponding to 20% below the ventilatory threshold I; n = 23) programme for a period of 6 months. All participants also received a multidisciplinary therapy that included nutritional, psychological and clinical counselling. Both HIT and LIT sessions were isocaloric, with energy expenditure set at 350 kcal. BP, HR and HRV were measured along with markers of body adiposity and insulin resistance before and after the respective interventions. RESULTS: The participants in both groups had similar physical and clinical characteristics. After the 6-month intervention, systolic, diastolic and mean BP decreased (P < 0.05, for all) similarly in both groups, whereas waist circumference, HR and HRV showed beneficial changes only in the HIT group (P < 0.05). CONCLUSION: Aerobic exercise training set at a high intensity compared with the low intensity appears to have additional benefits on abdominal obesity and cardiovascular health in that it enhances the parasympathetic and autonomic modulation of the heart in obese adolescents.

Forage-based dairying in a water-limited future: use of models to investigate farming system adaptation in southern Australia.

The irrigated dairy industry in southern Australia has experienced significant restrictions in irrigation water allocations since 2005, consistent with climate change impact predictions for the region. Simulation models of pasture growth (DairyMod), crop yield (Agricultural Production Systems Simulator, APSIM), and dairy system management and production (UDDER) were used in combination to investigate a range of forage options that may be capable of sustaining dairy business profitability under restricted water-allocation scenarios in northern Victoria, Australia. A total of 23 scenarios were simulated and compared with a base farm system (100% of historical water allocations, grazed perennial ryegrass pasture with supplements; estimated operating surplus $A2,615/ha at a milk price of $A4.14/kg of milk solids). Nine simulations explored the response of the base farm to changes in stocking rate or the implementation of a double cropping rotation on 30% of farm area, or both. Five simulations explored the extreme scenario of dairying without any irrigation water. Two general responses to water restrictions were investigated in a further 9 simulations. Annual ryegrass grazed pasture, complemented by a double cropping rotation (maize grown in summer for silage, followed by either brassica forage crop and annual ryegrass for silage in winter and spring) on 30% of farm area, led to an estimated operating surplus of $A1746/ha at the same stocking rate as the base farm when calving was moved to autumn (instead of late winter, as in the base system). Estimated total irrigation water use was 2.7ML/ha compared with 5.4ML/ha for the base system. Summer-dormant perennial grass plus double cropping (30% of farm area) lifted operating surplus by a further $A100/ha if associated with autumn calving (estimated total irrigation water use 3.1ML/ha). Large shifts in the forage base of dairy farms could sustain profitability in the face of lower, and fluctuating, water allocations. However, changes in other strategic management policies, notably calving date and stocking rate, would be required, and these systems would be more complex to manage. The adaptation scenarios that resulted in the highest estimated operating surplus were those where at least 10 t of pasture or crop DM was grazed directly by cows per hectare per year, resulting in grazed pasture intake of at least 2 t of DM/cow, and at least 60% of all homegrown feed that was consumed was grazed directly.

Weight-loss maintenance in successful weight losers: surgical vs non-surgical methods.

OBJECTIVE: As large weight losses are rarely achieved through any method except bariatric surgery, there have been no studies comparing individuals who initially lost large amounts of weight through bariatric surgery or non-surgical means. The National Weight Control Registry (NWCR) provides a resource for making such unique comparisons. This study compared the amount of weight regain, behaviors and psychological characteristics in NWCR participants who were equally successful in losing and maintaining large amounts of weight through either bariatric surgery or non-surgical methods. DESIGN: Surgical participants (n=105) were matched with two non-surgical participants (n=210) on gender, entry weight, maximum weight loss and weight-maintenance duration, and compared prospectively over 1 year. RESULTS: Participants in the surgical and non-surgical groups reported having lost approximately 56 kg and keeping > or =13.6 kg off for 5.5+/-7.1 years. Both groups gained small but significant amounts of weight from registry entry to 1 year (P=0.034), but did not significantly differ in magnitude of weight regain (1.8+/-7.5 and 1.7+/-7.0 kg for surgical and non-surgical groups, respectively; P=0.369). Surgical participants reported less physical activity, more fast food and fat consumption, less dietary restraint, and higher depression and stress at entry and 1 year. Higher levels of disinhibition at entry and increased disinhibition over 1 year were related to weight regain in both groups. CONCLUSIONS: Despite marked behavioral differences between the groups, significant differences in weight regain were not observed. The findings suggest that weight-loss maintenance comparable with that after bariatric surgery can be accomplished through non-surgical methods with more intensive behavioral efforts. Increased susceptibility to cues that trigger overeating may increase risk of weight regain regardless of initial weight-loss method.

PROCEED: Prospective Obesity Cohort of Economic Evaluation and Determinants: baseline health and healthcare utilization of the US sample.

AIM: To summarize baseline characteristics, health conditions, resource utilization and resource cost for the US population for the 90-day period preceding enrolment, stratified by body mass index (BMI) and the presence of abdominal obesity (AO). METHODS: PROCEED (Prospective Obesity Cohort of Economic Evaluation and Determinants) is a multinational, prospective cohort of control (BMI 20-24.0 kg/m(2)), overweight (BMI 25-29.9 kg/m(2)) and obese (BMI >or= 30 kg/m(2)) subjects with AO and without AO [non-abdominal obesity (NAO)], defined by waist circumference (WC) >102 and 88 cm for males and females, respectively. Subjects were recruited from an Internet consumer panel. Outcomes were self-reported online. Self-reported anthropometric data were validated. Prevalence of conditions and utilization is presented by BMI class and AO within BMI class. Differences in prevalence and means were evaluated. RESULTS: A total of 1067 overweight [n = 474 (NAO: n = 254 and AO: n = 220)] and obese [n = 493 (NAO: n = 39 and AO: n = 454)] subjects and 100 controls were recruited. Self-reported weight (r = 0.92) and WC (r = 0.87) were correlated with measured assessments. Prevalence of symptoms was significantly higher in groups with higher BMI, as were hypertension (p < 0.0001), diabetes (p < 0.0001) and sleep apnoea (p < 0.0001). Metabolic risk factors increased with the BMI class. Among the overweight class, subjects with AO had significantly more reported respiratory, heart, nervous, skin and reproductive system symptoms. Overweight subjects with AO reported a significantly higher prevalence of diabetes (13%) compared with overweight subjects with NAO (7%, p = 0.04). Mean healthcare cost was significantly higher in the higher BMI classes [control ($456 +/- 937) vs. overweight ($1084 +/- 3531) and obese ($1186 +/- 2808) (p < 0.0001)]. CONCLUSION: An increasing gradient of symptoms, medical conditions, metabolic risk factors and healthcare utilization among those with a greater degree of obesity was observed. The independent effect of AO on health and healthcare utilization deserves further study with a larger sample size.

International strategies to address obesity.

Obesity rates are increasing in most countries throughout the world. The reasons for the increase are complex and involve biological, behavioural and environmental factors. We have unintentionally created environments that encourage over-eating and discourage physical activity. Despite the recognition of the seriousness of obesity to public health, no interventions have been effective in reducing obesity rates on a population basis. Reversing obesity rates within populations will require addressing both individual behaviour and the obesogenic environment. Obesity rates could be reduced by treating affected individuals or by preventing the gradual increase in body weights of the population. Success in long-term obesity treatment is poor and appears to require that large behaviour changes be made and sustained. An alternative approach is to promote small lifestyle changes to prevent the gradual increase in the body weight of populations. America On the Move is an initiative based on promoting small lifestyle changes to prevent weight gain in the US population. This is one strategy could be used in other countries to reduce obesity rates.

Effects of long-term aerobic exercise on EPOC.

This study sought to determine the influence of 16 months of progressive aerobic exercise on excess postexercise oxygen consumption (EPOC) and the extent EPOC contributed to weight management. Twenty-five overweight/obese women and 16 overweight/obese men participated in a 16-month exercise program (moderate-intensity treadmill walking) that progressed across the first 26 weeks to 5 days.wk(-1), 45 min.session(-1), and 75% HRR. Three-hour EPOC was measured at baseline, 9 months, and 16 months by indirect calorimetry in response to an exercise session (treadmill walking), in which energy expenditure (EE) was estimated from the participant's previous 10 exercise sessions. For women, EPOC was 7.5 +/- 4.9, 9.6 +/- 7.6, and 6.5 +/- 6.5 L at baseline, 9 months, and 16 months, respectively (p > 0.05). For men, EPOC increased from baseline (11.8 +/- 6.8 L) to 9 months (13.5 +/- 8.6 L) (p < 0.05) with no further increase at 16 months (13.5 +/- 11.0 L). Change in EPOC was correlated with change in EE at 9 months (r = 0.65; p < 0.05) and 16 months (r = 0.58; p < 0.05) for men but not women. Progressive long-term exercise significantly influenced EPOC in overweight/obese men but not women. Change in volume of exercise likely explained the increase in energy expenditure during EPOC in men. EPOC contributed modestly to EE compared to the exercise itself.

Weight gain model in prepubertal rats: prediction and phenotyping of obesity-prone animals at normal body weight.

OBJECTIVE: Male Sprague-Dawley rats maintained from birth on a high-fat diet were examined to determine whether a specific measure before puberty can identify and allow one to characterize prepubertal rats at normal weight with high vs low risk for adult obesity. MATERIALS AND METHODS: Measures from weaning (day 21) to around puberty (day 45) were taken of weight gain, absolute body weight and daily energy intake on a high-fat diet and related to the amount of body fat accumulated at maturity (80-100 days of age). Rats identified by a specific prepubertal measure as obesity-prone (OP) vs obesity-resistant (OR) were then characterized before and after puberty. RESULTS: Prepubertal weight gain from days 30 to 35 of age was the strongest and earliest positive correlate of ultimate body fat accrual in adult rats. The highest (8-10 g/day) compared to lowest (5-7 g/day) weight-gain scores identified accurately and reproducibly distinct OP and OR subgroups at day 35 that became obese or remained lean, respectively, as adults. The OP rats with rapid prepubertal weight gain and 50% greater adiposity at maturity (day 100) exhibited the expected phenotype of already-obese rats. These included elevated levels of leptin, insulin, triglycerides and glucose, increased galanin (GAL) peptide levels in the paraventricular nucleus (PVN) and reduced neuropeptide Y (NPY) levels in the arcuate nucleus (ARC). Before puberty (day 35), the OP rats with normal fat pad weights, energy intake and endocrine profile similar to OR rats exhibited these disturbances characteristic of obese rats. They had decreased capacity for fat oxidation in muscle, increased GAL expression in PVN and reduced expression of NPY and agouti-related protein in ARC. CONCLUSION: Prepubertal weight gain can identify OP rats on day 35 when they have minimal body fat but exhibit specific metabolic and neurochemical disturbances expected to promote obesity and characteristics of already-obese adult rats.

The role of public policy in treating the epidemic of global obesity.

Given the powerful forces promoting population weight gain, the obesity epidemic cannot be reversed solely by promoting individual behavior change. Policy initiatives might lessen the impact of the biological and economical forces promoting weight gain or provide motivation to resist these forces. Unfortunately, there is little information to adequately evaluate the many policies that have been suggested. The intent of this review is to discuss the potential use of policy to stem the global epidemic of obesity.

Successful dieters have increased neural activity in cortical areas involved in the control of behavior.

OBJECTIVE: To investigate whether dietary restraint, a landmark of successful dieting, is associated with specific patterns of brain responses to the sensory experience of food and meal consumption. DESIGN AND SUBJECTS: Cross-sectional study of the brain's response to the sensory experience of food and meal consumption in nine successful dieters (age: 38+/-7 years, body fat (%): 28+/-3) and 20 non-dieters (age: 31+/-9 years, body fat (%): 33+/-9), all women. MEASUREMENTS: Changes in brain activity in response to the sensory experience of food and meal consumption were assessed by using positron emission tomography and (15)O water as a radiotracer. Body fatness was assessed by dual X-ray absorptiometry. Subjective ratings of hunger and fullness were measured by visual analogue scale. Dietary restraint, disinhibition and hunger were assessed by the Three Factor Eating Questionnaire. RESULTS: Successful dieters had a significantly higher level of dietary restraint compared to non-dieters. In response to meal consumption, successful dieters had a greater activation in the dorsal prefrontal cortex (DPFC), dorsal striatum and anterior cerebellar lobe as compared to non-dieters. In response to the same stimulation, the orbitofrontal cortex (OFC) was significantly more activated in non-dieters as compared to successful dieters. Dietary restraint was positively correlated with the response in the DPFC and negatively with the response in the OFC. The responses in the DPFC and OFC were negatively intercorrelated. CONCLUSION: Cortical areas involved in controlling inappropriate behavioral responses, such as the DPFC, are particularly activated in successful dieters in response to meal consumption. The association between the degree of dietary restraint and the coordinated neural changes in the DPFC and OFC raises the possibility that cognitive control of food intake is achieved by modulating neural circuits controlling food reward.

Model for predicting and phenotyping at normal weight the long-term propensity for obesity in Sprague-Dawley rats.

Tests were conducted to determine whether weight gain or nutrient intake measures during the first week of exposure to a macronutrient diet can accurately predict an animal's long-term propensity towards obesity. In multiple groups of normal-weight Sprague-Dawley rats (n=35-70/group), daily weight gain during the first 5 days on a high-fat diet (45-60% fat) was found to be strongly, positively correlated (r=+0.71 to r=+0.82) with accumulated body fat in 4 dissected depots after 4-6 weeks on the diet. This measure consistently identified obesity-prone (OP) rats which, relative to the obesity-resistant (OR) rats, were only slightly heavier (+15 g, 4%) and hyperphagic (+9 kcal, 8%) after 5 days but markedly heavier (+70g) with up to 2-fold greater fat mass after several weeks on the diet. Other dietary conditions and measures revealed weaker relationships to ultimate body fat accrual. The OP rats identified by their 5-day weight-gain score exhibited at this early stage clear disturbances characteristic of markedly obese rats. These included elevated leptin, insulin, triglycerides and glucose, along with increased lipoprotein lipase activity (LPL) in adipose tissue and galanin expression in the paraventricular nucleus. Most notable were significant reductions in muscle of LPL activity and ratio of beta-hydroxyacyl-CoA dehydrogenase to citrate synthase activity, indicating a decline in lipid transport and capacity of muscle to metabolize lipids. By occurring early with initial weight gain, these hypothalamic and metabolic disturbances in OP rats, favoring fat storage in adipose tissue over fat oxidation in muscle, may have causal relationships to long-term accumulation of body fat.

Different forms of obesity as a function of diet composition.

OBJECTIVE: To characterize the phenotype of obesity on a high-carbohydrate diet (HCD) as compared to a high-fat diet (HFD) or moderate-fat diet (MFD). METHODS AND PROCEDURES: In four experiments, adult Sprague-Dawley rats (275-300 g) were maintained for several weeks on a: (1) HFD with 50% fat; (2) balanced MFD with 25% fat; or (3) HCD with 10% fat/65% carbohydrate. Then, based on the amount of body fat accumulated in four dissected fat pads, the animals were subgrouped as lean (lowest tertile) or obese (highest tertile) and characterized with multiple measures. RESULTS: The obese rats of these diet groups, with 70-80% greater body fat than the lean animals, exhibited elevated levels of leptin and insulin and increased activity of lipoprotein lipase in adipose tissue (aLPL), with no change in muscle LPL. Characteristics common to the obese rats on the HFD or MFD, but not seen on the HCD, were hyperphagia, elevated circulating levels of triglycerides (TG), nonesterified fatty acids (NEFA) and glucose, and a significant increase in beta-hydroxyacyl-CoA dehydrogenase (HADH) activity in muscle, reflecting its greater capacity to metabolize fat. This was accompanied by a significant increase in expression of the peptide, galanin (GAL), in the paraventricular nucleus (PVN), as measured by in situ hybridization and real-time quantitative PCR, and also in GAL peptide immunoreactivity. These measures of GAL were consistently, positively correlated with circulating TG levels and also with HADH activity in muscle. In contrast to these fat-associated changes, rats that became obese on an HCD maintained normal caloric intake and levels of TG, NEFA, and glucose. They also showed no change in PVN GAL mRNA or peptide. Instead, they exhibited a significant reduction in HADH activity compared to the lean animals, along with increased activity of phosphofructokinase in muscle, a key enzyme in glycolysis. CONCLUSION: Specific characteristics of obesity, including expression of hypothalamic peptides, are dependent upon diet composition. Whereas obesity on an HFD is associated with hyperphagia and elevated lipids, fat metabolism in muscle, and fat-stimulated peptides such as GAL, obesity on an HCD with a similar increase in body fat shows none of these characteristics and instead exhibits a metabolic pattern in muscle that favors carbohydrate over fat oxidation. These results suggest the existence of multiple forms of obesity with different underlying mechanisms that are diet dependent.

A comparison of three methods of analyzing post-exercise oxygen consumption.

Oxygen consumption after exercise is frequently plotted as a function of time and then the area under the curve (AUC) is calculated. Subsequently, this AUC is further manipulated and thus, differences between these manipulations may impact the interpretation of changes in oxygen consumption after exercise. The purpose of this study was to determine if the method of calculating AUC influences the interpretation of changes in post-exercise oxygen consumption in response to long-term aerobic exercise. Forty-three moderately obese, sedentary participants volunteered to participate in this study (26 women and 17 men). All participants performed verified supervised exercise during the study. Supervised treadmill exercise was initially conducted for 3 d/week at 60 % of heart rate reserve (HRR) for 30 min and progressed to 5 d/week at 75 % of HRR for 45 min across the first 4 months. Pre-exercise, exercise, and post-exercise oxygen consumption was measured at baseline and 9 months. AUC was calculated by three methods; total, incremental, and positive incremental. Descriptive statistics and dependent T-tests were calculated for each method of calculating the AUC. In addition, the intra-individual coefficient of variation was determined for each individual for each AUC method. A pearson product moment correlation was calculated for each method to determine the strength of the relationship between pre- and post-training values. The change in post-exercise oxygen AUC after nine months of training was 5.36+/-10.90 L, 2.17+/-7.61 L, and 1.74+/-9.10 L for the total, incremental, and positive incremental methods, respectively. There was significant change in post-exercise total AUC from baseline to 9-months (5.36 +/- 10.90 L), while there was no significant change in incremental or positive incremental AUC. There was a moderately high correlation (r=0.67, p <0.05) between baseline and 9-months for the total AUC method, while there was no significant correlation for incremental and positive incremental AUC methods. These results suggest that the method used to calculate AUC can lead to a different interpretation of the effects of training on post-exercise oxygen consumption. From this data, it appears that analyzing post exercise oxygen consumption with the total area under the curve method has a greater ability to detect a change from aerobic training, than either the positive or incremental area under the curve methods.