Enhanced metabolic efficiency contributes to weight regain after weight loss in obesity-prone rats

Metabolic adjustments occur with weight loss that may contribute to a high rate of weight regain. We have previously observed in obesity-prone, obese rats that weight reduction is accompanied by a suppression in resting metabolic rate beyond what would be predicted for the change in metabolic mass. In the present study, we examine if this adjustment in metabolic efficiency is affected by the length of time in weight maintenance and if it contributes to the propensity to regain after weight loss. Twenty-four-hour, nonresting, and resting energy expenditure (REE) were obtained by indirect calorimetry and normalized to metabolic mass estimated by dual-energy X-ray absorptiometry. A 10% loss in body weight in weight-reduced rats was accompanied by a 15% suppression in adjusted REE. This enhancement in metabolic efficiency was not altered with either 8 or 16 wk of weight maintenance, but it did resolve when the forced control of intake was removed and the weight was regained. The rate of weight regain increased with the time in weight maintenance and was exceptionally high early during the relapse period. During this high rate of weight gain, the suppression in REE persists while consumption increases to a level that is higher than when they were obese. In summary, an enhanced metabolic efficiency and an elevated appetite both contribute (60% and 40%, respectively) to a large potential energy imbalance that, when the forcible control of energy intake is relieved, becomes actualized and results in an exceptionally high rate of weight regain.     

Contributing factors and variability of energy expenditure in non-obese, obese, and post-obese adolescents

Energy expenditure (EE) is a major determinant of energy balance and body composition. The objectives of this paper were to review the contributing factors of the main components of daily EE (DEE) and the inter-individual variability in these components in non-obese (NOb), obese (Ob), and post-obese (POb) adolescents. Body composition especially fat-free mass (FFM), is the major determinant of the basal metabolic rate which contributes 50-70% of DEE, whereas fat mass (FM) is a significant factor only in obese subjects. Physical activity is the second main variation factor of DEE, whereas growth, the thermic effect of food, and thermoregulation are generally of marginal importance. The energy costs and EE associated with various sedentary and physical activities were assessed in NOb, Ob and POb subjects both in standardised and in free-living conditions. The interindividual variability of DEE is high, even after adjustment for body composition, mainly because of great differences in time devoted to the various physical activities. DEE and EE associated with sleep and sedentary activities are significantly higher in Ob than in NOb, but not after adjustment for FFM. On the contrary, EE associated with physical activities is not significantly different between Ob and NOb adolescents, but 61% lower in Ob subjects after adjustment for body composition. Multidisciplinary weight-reduction programmes including moderate energy restriction and physical training result in great FM loss, maintenance of FFM, improvement of physical capacities, but reductions in organ and tissue metabolic rate and in EE associated with the various sedentary and physical activities, which may favour body weight regain in the less active POb subjects.     

Exercise reduces appetite and traffics excess nutrients away from energetically efficient pathways of lipid deposition during the early stages of weight regain

The impact of regular exercise on energy balance, fuel utilization, and nutrient availability, during weight regain was studied in obese rats, which had lost 17% of their weight by a calorie-restricted, low-fat diet. Weight reduced rats were maintained for 6 wk with and without regular treadmill exercise (1 h/day, 6 days/wk, 15 m/min). In vivo tracers and indirect calorimetry were then used in combination to examine nutrient metabolism during weight maintenance (in energy balance) and during the first day of relapse when allowed to eat ad libitum (relapse). An additional group of relapsing, sedentary rats were provided just enough calories to create the same positive energy imbalance as the relapsing, exercised rats. Exercise attenuated the energy imbalance by 50%, reducing appetite and increasing energy requirements. Expenditure increased beyond the energetic cost of the exercise bout, as exercised rats expended more energy to store the same nutrient excess in sedentary rats with the matched energy imbalance. Compared with sedentary rats with the same energy imbalance, exercised rats exhibited the trafficking of dietary fat toward oxidation and away from storage in adipose tissue, as well as a higher net retention of fuel via de novo lipogenesis in adipose tissue. These metabolic changes in relapse were preceded by an increase in the skeletal muscle expression of genes involved in lipid uptake, mobilization, and oxidation. Our observations reveal a favorable shift in fuel utilization with regular exercise that increases the energetic cost of storing excess nutrients during relapse and alterations in circulating nutrients that may affect appetite. The attenuation of the biological drive to regain weight, involving both central and peripheral aspects of energy homeostasis, may explain, in part, the utility of regular exercise in preventing weight regain after weight loss.     

Induction of ketosis in rats fed low-carbohydrate, high-fat diets depends on the relative abundance of dietary fat and protein

Low-carbohydrate/high-fat diets (LC-HFDs) in rodent models have been implicated with both weight loss and as a therapeutic approach to treat neurological diseases. LC-HFDs are known to induce ketosis; however, systematic studies analyzing the impact of the macronutrient composition on ketosis induction and weight loss success are lacking. Male Wistar rats were pair-fed for 4 wk either a standard chow diet or one of three different LC-HFDs, which only differed in the relative abundance of fat and protein (percentages of fat/protein in dry matter: LC-75/10; LC-65/20; LC-55/30). We subsequently measured body composition by nuclear magnetic resonance (NMR), analyzed blood chemistry and urine acetone content, evaluated gene expression changes of key ketogenic and gluconeogenic genes, and measured energy expenditure (EE) and locomotor activity (LA) during the first 4 days and after 3 wk on the respective diets. Compared with chow, rats fed with LC-75/10, LC-65/20, and LC-55/30 gained significantly less body weight. Reductions in body weight were mainly due to lower lean body mass and paralleled by significantly increased fat mass. Levels of β-hydroxybutyate were significantly elevated feeding LC-75/10 and LC-65/20 but decreased in parallel to reductions in dietary fat. Acetone was about 16-fold higher with LC-75/10 only (P < 0.001). In contrast, rats fed with LC-55/30 were not ketotic. Serum fibroblast growth factor-21, hepatic mRNA expression of hydroxymethylglutaryl-CoA-lyase, peroxisome proliferator-activated receptor-γ coactivator-1α, and peroxisome proliferator-activated receptor-γ coactivator-1β were increased with LC-75/10 only. Expression of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase was downregulated by 50-70% in LC-HF groups. Furthermore, EE and LA were significantly decreased in all groups fed with LC-HFDs after 3 wk on the diets. In rats, the absence of dietary carbohydrates per se does not induce ketosis. LC-HFDs must be high in fat, but also low in protein contents to be clearly ketogenic. Independent of the macronutrient composition, LC-HFD-induced weight loss is not due to increased EE and LA.     

Peripheral metabolic responses to prolonged weight reduction that promote rapid, efficient regain in obesity-prone rats

Weight regain after weight loss is the most significant impediment to long-term weight reduction. We have developed a rodent paradigm that models the process of regain after weight loss, and we have employed both prospective and cross-sectional analyses to characterize the compensatory adaptations to weight reduction that may contribute to the propensity to regain lost weight. Obese rats were fed an energy-restricted (50-60% kcal) low-fat diet that reduced body weight by 14%. This reduced weight was maintained for up to 16 wk with limited provisions of the low-fat diet. Intake restriction was then removed, and the rats were followed for 56 days as they relapsed to the obese state. Prolonged weight reduction was accompanied by 1) a persistent energy gap resulting from an increased drive to eat and a reduced expenditure of energy, 2) a higher caloric efficiency of regain that may be linked with suppressed lipid utilization early in the relapse process, 3) preferential lipid accumulation in adipose tissue accompanied by adipocyte hyperplasia, and 4) humoral adiposity signals that underestimate the level of peripheral adiposity and likely influence the neural pathways controlling energy balance. Taken together, long-term weight reduction in this rodent paradigm is accompanied by a number of interrelated compensatory adjustments in the periphery that work together to promote rapid and efficient weight regain. These metabolic adjustments to weight reduction are discussed in the context of a homeostatic feedback system that controls body weight.     

Predictors of Long‐term Weight Maintenance

Objective: The purpose of this study was to evaluate available variables of a long‐term weight maintenance study to investigate possible factors predisposing to weight regain after a period of weight loss. Research Methods and Procedures: The Maastricht Weight Maintenance Study is an ongoing longitudinal study of healthy men and women (29 men and 62 women; 18 to 65 years of age; BMI = 30.2 ± 3.1 kg/m²). A variety of parameters were measured before and after a very‐low‐energy diet and after a follow‐up of at least 2 years. Results: Mean weight loss was 7.9 ± 3.6 kg, and percent weight regain was 113.8 ± 98.1%. Percent BMI regain was negatively associated with an increase in dietary restraint (r = ?0.47, p < 0.05). Percent weight regain was negatively correlated with baseline resting metabolic rate (r = ?0.38, p = 0.01) and baseline fat mass (r = ?0.24, p = 0.05) and positively correlated with the magnitude of change in body weight (BW) expressed as maximum amplitude of BW (r = 0.21, p < 0.05). In addition, amplitude of BW was positively correlated with the frequency of dieting (r = 0.57, p < 0.01). Discussion: The best predictors for weight maintenance after weight loss were an increase in dietary restraint during weight loss, a high baseline resting metabolic rate, a relatively high baseline fat mass favoring a fat‐free mass–sparing effect during weight loss, a rather stable BW, and a low frequency of dieting. Therefore, BW maintenance after BW loss seems to be a multifactorial issue, including mechanisms that regulate an individuals’ energy expenditure, body composition, and eating behavior in such a way that energy homeostasis is maintained.     

A combined healthy strategy for successful weight loss,weight maintenance and improvement of hepatic lipid metabolism

Obesity is critically related with the development of metabolic and pathophysiological alterations among which non-alcoholic fatty liver disease (NAFLD) is of especial relevance. Although there are numerous strategies to successfully treat obesity, the prevention of weight regain still remains challenging for individuals who have undergone weight loss programs. In such context, diet and physical activity are considered essential for the regulation of body weight and lipid metabolism. In this study, rats were fed a high-fat diet (HFD) to induce obesity and alterations in hepatic lipid metabolism. Obese rats were then treated with single or combined strategies of caloric restriction, physical exercise, and/or pharmacological treatment with an appetite suppressant, to lose weight, reverse the obesity-related alterations in hepatic morphology and lipid metabolism and maintain the beneficial effects of the interventions used. HFD induced excess body weight, hepatic steatosis, altered fatty acid profile, dysregulated gene expression of lipogenic and lipolytic enzymes, as well as plasma markers of liver damage, and modifications in liver antioxidant enzyme activity. Such alterations were ameliorated by caloric restriction in combination with a mixed training protocol and/or food-intake inhibitor administration during a weight loss intervention period of 3 weeks, and the beneficial effects remained after 6 weeks of weight maintenance, with some interesting interactions observed. In conclusion, weight loss strategies assayed were efficient at correcting the obesogenic action of a HFD and related alterations in hepatic functionality through different molecular mechanisms. The beneficial effects were also evident along the post-intervention maintenance period to avoid body weight regain.     

Greater Than Predicted Decrease in Resting Energy Expenditure and Weight Loss: Results From a Systematic Review

Changes in resting energy expenditure (EE) during weight loss are said to be greater than what can be expected from changes of body mass, i.e., fat mass (FM) and fat‐free mass (FFM) but controversy persists. The primary focus of this study was to investigate whether there is a greater than predicted decrease in resting EE during weight loss in a large sample size through a systematic review. The study data were weighted and a partial residual plot followed by a multiple regression analysis was performed to determine whether FM and FFM can predict the changes of resting EE after weight loss. Another subgroup of studies from which all necessary information was available was analyzed and compared against the Harris—Benedict (HB) prediction equation to determine whether the changes in resting EE were greater than what was expected. Subjects lost 9.4 ± 5.5 kg (P < 0.01) with a mean resting EE decline of 126.4 ± 78.1 kcal/day (P < 0.01). Changes in FM and FFM explained 76.5% and 79.3% of the variance seen in absolute resting EE at baseline and post‐weight loss, respectively (P < 0.01). Analysis of the 1,450 subject subgroup indicated an ～29.1% greater than predicted decrease in resting EE when compared to the HB prediction equation (P < 0.01). This analysis does not support the notion of a greater than predicted decrease in resting EE after weight loss.     

Body mass, body composition and sleeping metabolic rate before, during and after endurance training

Metabolic rate, more specifically resting metabolic rate (RMR) or sleeping metabolic rate (SMR), of an adult subject is usually expressed as a function of the fat-free mass (FFM). Chronic exercise is thought to increase FFM and thus to increase RMR and SMR. We determined body mass (BM), body composition, and SMR before, during, and after an endurance training programme without interfering with energy intake. The subjects were 11 women and 12 men, aged 37 (SD 3) years and body mass index 22.3 (SD 1.5) kg · m^–2. The endurance training prepared subjects to run a half marathon competition after 44 weeks. The SMR was measured overnight in a respiration chamber. Body composition was measured by hydrostatic weighing. Measurements were performed at 0, 8, 20, 40, and 90 weeks after the start of the training. The BM had decreased from a mean value of 66.6 (SD 6.9) to 65.6 (SD 6.7) kg (P<0.01), fat mass (FM) had decreased from 17.1 (SD 3.9) to 13.5 (SD 3.6) kg (P<0.001), and FFM had increased from 49.5 (SD 7.3) to 52.2 (SD 7.6) kg (P<0.001) at 40 weeks. Mean SMR before and after 40 weeks training was 6.5 (SD 0.7) and 6.2 (SD 0.6) MJ · day^–1 (P<0.05). The decrease in SMR was related to the decrease in BM (r=0.62,P=0.001). At 90 weeks, when most subjects had not trained for nearly a year, BM and SMR were not significantly different from the initial value while FM and FFM had not changed since week 40 of training. In conclusion, it was found that an exercise induced increase in FFM did not result in an increase in SMR. There was an indication of the opposite effect, a decrease in SMR in the long term during training, possibly as a defence mechanism of the body in the maintenance of BM.     

Metabolic costs incurred by crayfish (Procambarus acutus) in a trace element-polluted habitat: further evidence of similar responses among diverse taxonomic groups

Recent studies of several vertebrates and an invertebrate have shown elevated standard metabolic rate (SMR) following chronic exposure to a mixture of trace elements in a contaminated habitat. In this study, we examined whether another invertebrate, a crayfish (Procambarus acutus), also experienced elevated SMR in response to the same contaminants. We compared SMR of individuals inhabiting the contaminated site with SMR of individuals from uncontaminated reference sites. We also examined SMR of individuals collected from the reference areas and exposed in the laboratory for 50 days to sediment and food derived from the contaminated site. Individuals collected from the contaminated site had elevated SMR compared to individuals collected from the unpolluted areas (25.1 vs. 19.2 J g^?1 day^?1). Individuals exposed to contaminated sediment and food in the laboratory experienced elevations in SMR compared to controls after 27 days of exposure (35.2 vs. 29.4 J g^?1 day^?1), but after 50 days of exposure, metabolic rate no longer differed between treatments. Growth of contaminant-exposed individuals was lower than growth of reference animals throughout the laboratory study. Elevated SMR associated with contaminant exposure may reflect energy-demanding mechanisms required to combat deleterious effects of contaminants. Our results support the prediction that increases in energy expenditure in the contaminated habitat would negatively influence production processes, such as growth. Results from this study in conjunction with observations from other species suggest that increased SMR is a common response among several taxa to the mixture of contaminants in the study site.     

Exercise training elevates RMR during moderate but not severe dietary restriction in obese male rats

This study examined the effects of 11 wk of exercise training (E) on resting O2 uptake (RMR) and the composition of diet-induced weight loss in obese male Sprague-Dawley rats (n = 48). The rats underwent one of three levels of dietary treatment: ad libitum (AL), moderate restriction (MR), and severe restriction (SR). Compared with AL-CC (cage confined; 647 +/- 13 g), the AL-E (84% of AL-CC), MR-CC (77%), MR-E (77%), SR-CC (63%), and SR-E (63%) groups were all reduced in body mass. At the MR level, E significantly reduced fat mass (FM; MR-CC 73 +/- 5, MR-E 45 +/- 5 g) and increased water mass (WM; MR-CC 307 +/- 5, MR-E 329 +/- 5 g) compared with CC. In contrast, no significant differences existed between the SR-CC and SR-E groups. Exercise training did not result in conservation of protein mass at any level of dietary intake. Exercise training significantly elevated RMR (on a kg0.75 basis) by approximately 7% for the AL-E and MR-E groups compared with their respective dietary counterparts. These findings may help reconcile the conflicting results present in the literature with respect to the effects of exercise training during diet-induced weight loss. That is, studies using relatively severe dietary restrictions are less likely to demonstrate exercise-induced changes in RMR, FM, and WM than those employing moderate dietary restrictions.     

Effects of leptin replacement alone and with exendin-4 on food intake and weight regain in weight-reduced diet-induced obese rats

Weight loss in obese humans produces a relative leptin deficiency, which is postulated to activate potent orexigenic and energy conservation mechanisms to restrict weight loss and promote weight regain. Here we determined whether leptin replacement alone or with GLP-1 receptor agonist exendin-4 attenuates weight regain or promotes greater weight loss in weight-reduced diet-induced obese (DIO) rats. Forty percent restriction in daily intake of a high-fat diet in DIO rats for 4 wk reduced body weight by 12%, body fat by 29%, and plasma leptin by 67% and normalized leptin sensitivity. When food restriction ended, body weight, body fat, and plasma leptin increased rapidly. Daily administration of leptin [3-h intraperitoneal (ip) infusions (4 nmol·kg(-1)·h(-1))] at onset and end of dark period for 3 wk did not attenuate hyperphagia and weight regain, nor did it affect mean daily meal sizes or meal numbers. Exendin-4 (50 pmol·kg(-1)·h(-1)) infusions during the same intervals prevented postrestriction hyperphagia and weight regain by normalizing meal size. Coadministration of leptin and exendin-4 did not reduce body weight more than exendin-4 alone. Instead, leptin began to attenuate the inhibitory effects of exendin-4 on food intake, meal size, and weight regain by the end of the second week of administration. Plasma leptin in rats receiving leptin was sevenfold greater than in rats receiving vehicle and 17-fold greater than in rats receiving exendin-4. Together, these results do not support the hypothesis that leptin replacement alone or with exendin-4 attenuates weight regain or promotes greater weight loss in weight-reduced DIO rats.     

Low‐carbohydrate High‐fat Diets: Regulation of Energy Balance and Body Weight Regain in Rats

The aim of the current investigations was to examine the effects of a low‐carbohydrate high‐fat diet (LC‐HFD) on body weight, body composition, growth hormone (GH), IGF‐I, and body weight regain after stopping the dietary intervention and returning the diet back to standard laboratory chow (CH). In study one, both adolescent and mature male Wistar rats were maintained on either an isocaloric LC‐HFD or CH for 16 days before having their diet switched. In study two, mature rats were maintained on either LC‐HFD or CH for 16 days to determine the effects of the LC‐HFD on fat pad weight. LC‐HFD leads to body weight loss in mature rats (P < 0.01) and lack of body weight gain in adolescent rats (P < 0.01). Despite less body weight, increased body fat was observed in rats maintained on LC‐HFD (P < 0.05). Leptin concentrations were higher (P < 0.05), and IGF‐I (P < 0.01) concentrations were reduced in the LC‐HFD rats. When the diet was returned to CH following LC‐HFD, body weight regain was above and beyond that which was lost (P < 0.01). The LC‐HFD resulted in increased body fat and had a negative effect upon both GH and IGF‐I concentrations, which might have implications for the accretion and maintenance of lean body mass (LBM), normal growth rate and overall metabolic health. Moreover, when the LC‐HFD ceases and a high‐carbohydrate diet follows, more body weight is regained as compared to when the LC‐HFD is consumed, in the absence of increased energy intake.     

Predicting changes of body weight, body fat, energy expenditure and metabolic fuel selection in C57BL/6 mice

The mouse is an important model organism for investigating the molecular mechanisms of body weight regulation, but a quantitative understanding of mouse energy metabolism remains lacking. Therefore, we created a mathematical model of mouse energy metabolism to predict dynamic changes of body weight, body fat, energy expenditure, and metabolic fuel selection. Based on the principle of energy balance, we constructed ordinary differential equations representing the dynamics of body fat mass (FM) and fat-free mass (FFM) as a function of dietary intake and energy expenditure (EE). The EE model included the cost of tissue deposition, physical activity, diet-induced thermogenesis, and the influence of FM and FFM on metabolic rate. The model was calibrated using previously published data and validated by comparing its predictions to measurements in five groups of male C57/BL6 mice (N = 30) provided ad libitum access to either chow or high fat diets for varying time periods. The mathematical model accurately predicted the observed body weight and FM changes. Physical activity was predicted to decrease immediately upon switching from the chow to the high fat diet and the model coefficients relating EE to FM and FFM agreed with previous independent estimates. Metabolic fuel selection was predicted to depend on a complex interplay between diet composition, the degree of energy imbalance, and body composition. This is the first validated mathematical model of mouse energy metabolism and it provides a quantitative framework for investigating energy balance relationships in mouse models of obesity and diabetes.     

Quantifying selection on standard metabolic rate and body mass in Drosophila melanogaster

Standard metabolic rate (SMR), defined as the minimal energy expenditure required for self‐maintenance, is a key physiological trait. Few studies have estimated its relationship with fitness, most notably in insects. This is presumably due to the difficulty of measuring SMR in a large number of very small individuals. Using high‐throughput flow‐through respirometry and a Drosophila melanogaster laboratory population adapted to a life cycle that facilitates fitness measures, we quantified SMR, body mass, and fitness in 515 female and 522 male adults. We used a novel multivariate approach to estimate linear and nonlinear selection differentials and gradients from the variance‐covariance matrix of fitness, SMR, and body mass, allowing traits specific covariates to be accommodated within a single model. In males, linear selection differentials for mass and SMR were positive and individually significant. Selection gradients were also positive but, despite substantial sample sizes, were nonsignificant due to increased uncertainty given strong SMR‐mass collinearity. In females, only nonlinear selection was detected and it appeared to act primarily on body size, although the individual gradients were again nonsignificant. Selection did not differ significantly between sexes although differences in the fitness surfaces suggest sex‐specific selection as an important topic for further study.     

Increased extracellular water compartment, relative to intracellular water compartment, after weight reduction.

The hydration of fat free mass (FFM) and extracellular (ECW) and intracellular water (ICW) compartments were studied in 30 obese premenopausal women before and after a 3-mo weight-reduction program and again after a 9-mo weight-maintenance program. Body fat was determined by a four-compartment model. Total body water and ECW were determined by deuterium dilution and bromide dilution, respectively. After the weight-reduction period, mean weight loss was 12.8 kg, and body fat was reduced on average by 10.9 kg. During weight maintenance, changes in body mass and body fat were not significant. Before weight reduction, mean ECW/ICW ratio was relatively high (0.78 +/- 0.10). During the the study, total body water and ICW did not change significantly. ECW did not change significantly after weight reduction, but 12 mo after the start ECW was significantly increased by 1 liter. The ECW/ICW ratio increased to 0.87 +/- 0.12 (month 12). The hydration of the FFM increased from 74 +/- 1 to 77 +/- 2% during the weight reduction and remained elevated during weight maintenance. In conclusion, the ECW/ICW ratio and the hydration of the FFM, did not normalize during weight reduction and weight maintenance.     

Defense of body weight against chronic caloric restriction in obesity-prone and -resistant rats

Half of Sprague-Dawley rats develop and defend diet-induced obesity (DIO) or diet resistance (DR) when fed a high-energy (HE) diet. Here, adult male rats were made DIO or DR after 10 wk on HE diet. Then half of each group was food restricted for 8 wk on chow to maintain their body weights at 90% of their respective baselines. Rate and magnitude of weight loss were comparable, but maintenance energy intake and the degree of sympathetic activity (24-h urine norepinephrine) inhibition were 17 and 29% lower, respectively, in restricted DR than DIO rats. Restricted DIO rats reduced adipose depot weights, plasma leptin, and insulin levels by 35%. Restricted DR rats reduced none of these. When fed ad libitum, both DR and DIO rats returned to the body weights of their respective chow-fed phenotype controls within 2 wk. This was associated with increased adipose mass and leptin and insulin levels only in DIO rats. Thus DR rats appear to alter primarily their lean body mass, whereas DIO rats primarily alter their adipose mass during chronic caloric restriction and refeeding.     

A Weight Reduction Program Preserves Fat‐Free Mass but Not Metabolic Rate in Obese Adolescents

Objective: To determine the effects of a multidisciplinary weight reduction program on body composition and energy expenditure (EE) in severely obese adolescents. Research Methods and Procedures: Twenty‐six severely obese adolescents, 12 to 16 years old [mean BMI: 33.9 kg/m²; 41.5% fat mass (FM)] followed a 9‐month weight reduction program including moderate energy restriction and progressive endurance and resistance training. Body composition was assessed by DXA, basal metabolic rate by indirect calorimetry, and EE by whole‐body indirect calorimetry with the same activity program over 36‐hour periods before starting and 9 months after the weight reduction period. Results: Adolescents gained (least‐square mean ± SE) 2.9 ± 0.2 cm in height, lost 16.9 ± 1.3 kg body weight (BW), 15.2 ± 0.9 kg FM, and 1.8 ± 0.5 kg fat‐free mass (FFM) (p < 0.001). Basal metabolic rate, sleeping, sedentary, and daily EE were 8% to 14% lower 9 months after starting (p < 0.001) and still 6% to 12% lower after adjustment for FFM (p < 0.05). Energy cost of walking decreased by 22% (p < 0.001). The reduction in heart rate during sleep and sedentary activities (?10 to ?13 beats/min), and walking (?20 to ?25 beats/min) (p < 0.001) resulted from both the decrease in BW and physical training. Discussion: A weight reduction program combining moderate energy restriction and physical training in severely obese adolescents resulted in great BW and FM losses and improvement of cardiovascular fitness but did not prevent the decline in EE even after adjustment for FFM.     

Sertraline and Relapse Prevention Training Following Treatment by Very-Low-Calorie Diet: A Controlled Clinical Trial

WADDEN, THOMAS A, SUSAN J BARTLETT, GARY D FOSTER, ROBERT A GREENSTEIN, BARBARA J WINGATE, ALBERT J STUNKARD AND KATHLEEN A LETIZIA. Sertraline and relapse prevention training following treatment by very-low-calorie diet: a controlled clinical trial. Obes Res. This study examined the combination of sertraline, a selective serotonin reuptake inhibitor, and relapse prevention training in the maintenance of weight loss following treatment by a very-low-calorie diet. A total of 53 women who had lost a mean (± SD) of 22.9 ± 7.1 kg from a pretreatment weight of 103.1 ± 17.8 kg were randomly assigned to a 54-week weight maintenance program that was combined with either: 1) 200 mg/d of sertraline; or 2) placebo. During the first 6 weeks, sertraline subjects lost significantly more weight and reported significantly greater reductions in hunger and preoccupation with food than did subjects on placebo. After this time, however, women in both conditions regained weight steadily. The 13 sertraline subjects who completed the 54-week study regained 17.7 ± 10.6 kg of their original 26.3 ± 7.6 kg loss, equal to a regain of 70.9 ± 41.7%. The 17 placebo completers regained 11.8 ± 9.0 kg of their 23.4 ± 7.8 kg loss, equal to a 46.5 ± 34.6% regain. End-of-treatment differences between groups in weight change were not statistically significant. Nor were there significant differences between the two conditions at any time in changes in fat-free mass, resting metabolic rate or dysphoria, all of which tended to increase with weight regain. The results are discussed in relation to findings from other long-term studies that combined diet and medication.     

Effects of wing polyphenism, aphid genotype and host plant chemistry on energy metabolism of the grain aphid, Sitobion avenae

Wing dimorphism has been proposed as a strategy to face trade-offs between flight capability and fecundity. In aphids, individuals with functional wings have slower development and lower fecundity compared with wingless individuals. However, differential maintenance costs between winged and wingless aphids have not been deeply investigated. In the current study, we studied the combined effect of wing dimorphism with the effects of aphid genotypes and of wheat hosts having different levels of chemical defences (hydroxamic acids, Hx) on adult body mass and standard metabolic rates (SMR) of winged and wingless morphs of the grain aphid, Sitobion avenae. We found that wingless aphids had higher body mass than winged aphids and that body mass also increased towards host with high Hx levels. Furthermore, winged aphids showed a plastic SMR in terms of Hx levels, whereas wingless aphids displayed a rigid reaction norm (significant interaction between morph condition and wheat host). These findings suggest that winged aphids have reduced adult size compared to wingless aphids, likely due to costs associated to the development of flight structure in early-life stages. These costs contrast with the absence of detectable metabolic costs related to fuelling and maintenance of the flight apparatus in adults.