Randomised comparison of diets for maintaining obese subjects' weight after major weight loss: ad lib,low fat,high carbohydrate diet v fixed energy intake.

OBJECTIVES: To compare importance of rate of initial weight loss for long term outcome in obese patients and to compare efficacy of two different weight maintenance programmes. DESIGN: Subjects were randomised to either rapid or slow initial weight loss. Completing patients were re-randomised to one year weight maintenance programme of ad lib diet or fixed energy intake diet. Patients were followed up one year later. SETTING: University research department in Copenhagen, Denmark. SUBJECTS: 43 (41 women) obese adults (body mass index 27-40) who were otherwise healthy living in or around Copenhagen. INTERVENTIONS: 8 weeks of low energy diet (2 MJ/day) or 17 weeks of conventional diet (5 MJ/day), both supported by an anorectic compound (ephedrine 20 mg and caffeine 200 mg thrice daily); one year weight maintenance programme of ad lib, low fat, high carbohydrate diet or fixed energy intake diet (< or = 7.8 MJ/day), both with reinforcement sessions 2-3 times monthly. MAIN OUTCOME MEASURES: Mean initial weight loss and proportion of patients maintaining a weight loss of > 5 kg at follow up. RESULTS: Mean initial weight loss was 12.6 kg (95% confidence interval 10.9 to 14.3 kg) in rapid weight loss group and 12.6 (9.9 to 15.3) kg in conventional diet group. Rate of initial weight loss had no effect on weight maintenance after 6 or 12 months of weight maintenance or at follow up. After weight maintenance programme, the ad lib group had maintained 13.2 (8.1 to 18.3) kg of the initial weight loss of 13.5 (11.4 to 15.5) kg, and the fixed energy intake group had maintained 9.7 (6.1 to 13.3) kg of the initial 13.8 (11.8 to 15.7) kg weight loss (group difference 3.5 (-2.4 to 9.3) kg). Regained weight at follow up was greater in fixed energy intake group than in ad lib group (11.3 (7.1 to 15.5) kg v 5.4 (2.3 to 8.6) kg, group difference 5.9 (0.7 to 11.1) kg, P < 0.03). At follow up, 65% of ad lib group and 40% of fixed energy intake group had maintained a weight loss of > 5 kg (P < 0.07). CONCLUSION: Ad lib, low fat, high carbohydrate diet was superior to fixed energy intake for maintaining weight after a major weight loss. The rate of the initial weight loss did not influence long term outcome.     

Provision of Foods Differing in Energy Density Affects Long‐Term Weight Loss

Objective: The energy density (kilocalories per gram) of foods influences short‐term energy intake. This 1‐year clinical trial tested the effect on weight loss of a diet incorporating one or two servings per day of foods equal in energy but differing in energy density. Research Methods and Procedures: Dietitians instructed 200 overweight and obese women and men to follow an exchange‐based energy‐restricted diet. Additionally, subjects were randomized to consume daily either one or two servings of low energy‐dense soup, two servings of high energy‐dense snack foods, or no special food (comparison group). Results: All four groups showed significant weight loss at 6 months that was well maintained at 12 months. The magnitude of weight loss, however, differed by group (p = 0.006). At 1 year, weight loss in the comparison (8.1 ± 1.1 kg) and two‐soup (7.2 ± 0.9 kg) groups was significantly greater than that in the two‐snack group (4.8 ± 0.7 kg); weight loss in the one‐soup group (6.1 ± 1.1 kg) did not differ significantly from other groups. Weight loss was significantly correlated with the decrease in dietary energy density from baseline at 1 and 2 months (p = 0.0001) but not at 6 and 12 months. Discussion: On an energy‐restricted diet, consuming two servings of low energy‐dense soup daily led to 50% greater weight loss than consuming the same amount of energy as high energy‐dense snack food. Regularly consuming foods that are low in energy density can be an effective strategy for weight management.     

Failure of Preoperative Resting Energy Expenditure in Predicting Weight Loss after Gastroplasty

Objective: To evaluate the predictive efficacy of preoperative resting energy expenditure (REE) on weight loss after vertical banded gastroplasty (VBG). When subjected to a gastric restriction procedure of similar extent, the patients with higher energy expenditure should experience a greater negative energy balance than those with lower‐energy expenditure, and thus, lose more weight, thereby making REE a reliable predictor of weight loss after VBG. Research Methods and Procedures: This was a prospective investigation after VBG, taking into account the relationship between preoperative REE values and the results at 1‐year follow‐up in terms of weight loss and success of the procedure. The correlations were evaluated by multiple and logistic regression analysis. Results: The weight loss and the outcome at 1 year after VBG seemed to be completely independent of preoperative energy expenditure. Discussion: These findings suggest that, despite gastric restriction, patients may voluntarily adjust their energy intake, and that the weight outcome after VBG is influenced more by behavioral and cognitive variables than by biological or surgical factors.     

Weight regain and health-related quality of life in postmenopausal women

Weight loss improves health-related quality of life (HRQoL). However, regain after loss is common; little is known about the impact of weight regain on HRQoL in postmenopausal women. Woman on the Move through Activity and Nutrition (WOMAN) is a randomized lifestyle intervention trial of diet, physical activity, and weight loss in 508 postmenopausal women aged 52-62 years. This analysis focused on the women who lost > or =5 lb during the initial phase of the study, baseline to 6 months (n = 248). This cohort was divided into three groups based on subsequent weight change between 6 and 18 months: weight loss (WL; > or =5 lb loss), weight stable (WS; <+/-5 lb change), and weight regain (WR; > or =5 lb gain). HRQoL was measured at baseline, 6, and 18 months using the Short Form-36. Of the 248 women studied, 51 (21%) continued to lose weight after initial weight loss, while 127 (51%) maintained a stable weight, and 70 (28%) regained weight. Between baseline and 6 months, women in WR group had decreased mental health and social-functioning scores, while the WL and WS groups improved in these subscales. Between baseline and 18 months, energy improved most significantly in those with continued weight loss (P = 0.0003). Weight loss was correlated with a small to moderate improvement in perceived general health and energy, which was reversed by weight gain. Further study is needed to investigate the impact of a decline in mental health and social functioning on future weight regain.     

Preferential loss of body fat during starvation in dietary obese rats.

This study was undertaken to examine whether diet-induced obesity alters the amount and/or composition of weight lost during starvation. The amount and composition of weight lost during a 4-day period of starvation was determined before and at 17, 30 and 42 weeks after rats (350 g of body weight) were given a high fat diet (HFD). To control for effects of aging, a second group of rats, fed standard laboratory chow, was also subjected to similar periods of starvation. Although total weight loss during starvation was never greater for HFD rats than for chow-fed rats, the former group showed a clear patter of increasing loss of body fat and total energy and conservation of fat-free tissues with periods of starvation later in life. In addition, chow-fed rats showed substantial energy conservation during each period of starvation (i.e. they lost less energy each day than their pre-starvation energy requirements). In contrast, HFD rats demonstrated substantial energy conservation only at 17 weeks and not at 30 or 42 weeks; during the last period of starvation, their average daily loss of carcass energy exceeded their pre-starvation energy requirements. This suggests the increased fat mass of these rats may have led to increased fuel availability and to an increased metabolic rate during starvation. If these results are applicable to humans, the more obese subjects are likely to show greater total loss of energy than lean subjects, but show a lesser loss of lean body mass, at least initially. If protein requirements are reflected by the ability to mobilize protein during food restriction, protein requirements would be substantially lower in the dietary obese rats than in controls. In summary, diet-induced obesity leads to preferential loss of body fat and conservation of lean mass during starvation.     

Pharmacological and Clinical Studies of Ephedrine and Other Thermogenic Agonists

When given as a supplement to an energy restricted diet the sympathomimetic agent ephedrine, in combination with methylxanthines such as caffeine, improves fat loss by dual actions: a central suppression of appetite and peripheral stimulation of energy expenditure covered by fat oxidation. Mean weight loss was found to be 16.6 kg after 6 months when E+C was given as an adjuvant to an efficient hypoenergetic diet, which was 3.4 kg higher than in the placebo group. An additional 24 weeks treatment with E+C prevented relapse. In the first weeks of treatment E+C offset the hypotensive effect of energy restriction and weight loss, but the effect was transient, and after 8 weeks blood pressures were indistinguishable from those of the placebo group. E+C has no adverse effect on glucose and lipid metabolism, but has been shown to prevent the decline in HDL-cholesterol caused by weight loss. In a comparative trial the weight loss produced by E+C was similar to that of dexfenfluramine. More research on sympathomimetics and methylxanthines should be carried out to identify combinations with improved efficiency and safety. Moreover, more long-term trials and studies in males are required.     

Body weight setpoint, metabolic adaption and human starvation

A biological setpoint for fatness has been proposed in the medical literature. This body weight setpoint functions as a point of stable equilibrium. In an underfed state, with resulting weight loss, the body will reduce the relative energy expenditure by metabolic adaption which reduces the rate of weight loss. Previous mathematical models of energy expenditure and weight loss dynamics have not addressed this setpoint mechanism. The setpoint model has been proposed to quantify this biological process and is unique in predicting energy expenditure during weight loss as a function of the setpoint fat-free mass ratio and setpoint energy expenditure, eliminating the various controlling characteristics such as age, gender and heredity. The model is applied to the seminal Minnesota human semistarvation experiment and is used to predict weight vs time on an individual basis and the caloric requirements for weight maintenance at the reduced weight. Comparison is made with the Harris-Benedict equations and the Brody-Kleiber. (W ^3/4) law.     

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.     

Weight-Loss Induced Changes in Physical Activity and Activity Energy Expenditure in Overweight and Obese Subjects before and after Energy Restriction

Activity energy expenditure (AEE) is the component of daily energy expenditure that is mainly influenced by the amount of physical activity (PA) and by the weight of the body displaced. This study aimed at analyzing the effect of weight loss on PA and AEE. The body weight and PA of 66 overweight and obese subjects were measured at baseline and after 12 weeks of 67% energy restriction. PA was measured using a tri-axial accelerometer for movement registration (Tracmor) and quantified in activity counts. Tracmor recordings were also processed using a classification algorithm to recognize 6 common activity types engaged in during the day. A doubly-labeled water validated equation based on Tracmor output was used to estimate AEE. After weight loss, body weight decreased by 13±4%, daily activity counts augmented by 9% (95% CI: +2%, +15%), and this increase was weakly associated with the decrease in body weight (R² = 7%; P<0.05). After weight loss subjects were significantly (P<0.05) less sedentary (–26 min/d), and increased the time spent walking (+11 min/d) and bicycling (+4 min/d). However, AEE decreased by 0.6±0.4 MJ/d after weight loss. On average, a 2-hour/day reduction of sedentary time by increasing ambulatory and generic activities was required to restore baseline levels of AEE. In conclusion, after weight loss PA increased but the related metabolic demand did not offset the reduction in AEE due to the lower body weight. Promoting physical activity according to the extent of weight loss might increase successfulness of weight maintenance.     

The efficiency of growth during body weight recovery in young adult female rats

1. Six young adult female rats were subjected to 40% body weight loss in 84 days by food restriction followed by recovery of body weight in 36.2 +/- 4.28 days by ad libitum food intake. The regimen was then repeated, with 40% body weight loss in 105 days followed by recovery of body weight in 22.8 +/- 2.00 days. 2. Food intakes were measured continuously. 3. These rats used digestible energy more efficiently during the second recovery (49.1 +/- 3.11 v. 77.3 +/- 7.91 kJ digestible energy intake per g body wt gain). 4. Seven rats were subjected to one body weight loss and recovery. Five of them had an efficiency of 44.1 +/- 3.34 kJ/g live wt gain which was not significantly different from that of the first group during their second recovery; they may not have been capable of improvement after a second deprivation. 5. It is concluded that some rats can adapt after a period of severe body weight loss and recovery to utilize food more efficiently during body weight recovery after a second episode.     

Increased energy intake minimizes weight loss in men at high altitude.

The hypothesis that high-altitude weight loss can be prevented by increasing energy intake to meet energy requirement was tested in seven men, 23.7 +/- 4.3 (SD) yr, taken to 4,300 m for 21 days. Energy intake required to maintain body weight at sea level was found to be 3,118 +/- 300 kcal/day, as confirmed by nitrogen balance. Basal metabolic rate (BMR), determined by indirect calorimetry, increased 27% on day 2 at altitude and then decreased and reached a plateau at 17% above the sea level BMR by day 10. Energy expended during strenuous activities was 37% lower at altitude than at sea level. Fecal excretion of energy, nitrogen, total fiber, and total volatile fatty acids was not significantly affected by altitude. Energy intake at altitude was adjusted after 1 wk, on the basis of the increased BMR, to 3,452 +/- 452 kcal/day. Mean nitrogen balance at altitude was negative (-0.25 +/- 0.71 g/day) before energy intake was adjusted but rose significantly thereafter (0.20 +/- 0.71 and 0.44 +/- 0.66 g/day during weeks 2 and 3). Mean body weight decreased 2.1 +/- 1.0 kg over the 3 wk of the study, but the rate of weight loss was significantly diminished after the increase in energy intake (201 +/- 75 vs. 72 +/- 48 g/day). Individual regression lines drawn through 7-day segments of body weight showed that in four of seven subjects the slopes of body weight were not significantly different from zero after the 2nd wk. Thus weight loss ceased in four of seven men in whom increased BMR at altitude was compensated with increased energy intake.(ABSTRACT TRUNCATED AT 250 WORDS)     

Amount of Food Group Variety Consumed in the Diet and Long‐Term Weight Loss Maintenance

Objective: Decreases in variety of foods consumed within high‐fat‐dense food groups and increases in variety of foods consumed within low‐fat‐dense food groups are associated with lower energy intake and greater weight loss during obesity treatment and may assist with weight loss maintenance. This study examined food group variety in 2237 weight loss maintainers in the National Weight Control Registry, who had lost 32.2 ± 18.0 kg (70.9 ± 39.5 lbs) and maintained a weight loss of at least 13.6 kg (30 lbs) for 6.1 ± 7.7 years. Research Methods and Procedures: At entry into the registry, registry members completed a food frequency questionnaire from which amount of variety consumed from different food groups was assessed. To provide a context for interpreting the level of variety occurring in the diet of registry participants, food group variety was compared between registry participants and 96 individuals who had recently participated in a behavioral weight loss program and had lost at least 7% of initial body weight. Results: Registry members reported consuming a diet with very low variety in all food groups, especially in those food groups higher in fat density. Registry participants consumed significantly (p < 0.001) less variety within all food groups, except fruit and combination foods, than recent weight losers after 6 months of weight loss treatment. Discussion: These results suggest that successful weight loss maintainers consume a diet with limited variety in all food groups. Restricting variety within all food groups may help with consuming a low‐energy diet and maintaining long‐term weight loss.     

Effects of Sibutramine on Resting Metabolic Rate and Weight Loss in Overweight Women

Sibutramine, a monoamine re-uptake inhibitor, has recently been approved by the Food and Drug Administration as a weight loss agent. Sibutramine lowers body-weight in rodents by reducing energy intake and increasing energy expenditure. Sibutramine facilitates weight loss in human subjects, but it is not clear whether it acts on energy intake, energy expenditure, or both. The present study was a randomized clinical trial designed to assess the effects of sibutramine (at 10 or 30 mg/day) on body weight and resting metabolic rate (RMR). Forty-four overweight women were randomized to 1) placebo (n=15); 2) sibutramine at 10 mg/day (n=15) or, 3) sibutramine at 30 mg/day (n=14). All subjects were instructed to consume a 1200 kcal/day diet for 8 weeks while receiving drug or placebo. RMR was assessed by indirect calorimetry at baseline, at 3 hours after the first dose of drug (or placebo), and at the end of the 8-week weight-loss period. Sibutramine reduced body weight-relative to placebo, but there was no difference between weight loss on the two sibutramine doses. No significant differences in RMR between sibutramine and placebo were seen, either 3-hour post dose or after the 8-week weight-loss period. After the weight loss period, all groups were taken off medication and kept weight stable for another 4 weeks. RMR was measured again and was not different among groups. That there was no change in RMR when sibutramine was stopped further suggests that the drug does not directly affect RMR. In summary, while sibutramine was shown to be an effective weightloss agent over 8 weeks, we found no evidence that it increased RMR.     

Lifestyle intervention leading to moderate weight loss normalizes postprandial triacylglycerolemia despite persisting obesity

Obesity is associated with impaired postprandial triacylglycerolemia, an independent risk factor for cardiovascular disease. Given that obesity is hard to treat, efforts should focus on treating its comorbidities. We aimed to investigate whether moderate weight loss normalizes postprandial triacylglycerol (TAG) concentrations, in the absence of the acute effects of negative energy balance. For this purpose, postprandial lipemia was investigated in eight obese but otherwise healthy, sedentary men (age: 41.3 ± 4.1 years, BMI: 36.5 ± 1.6 kg·m(-2)), once before and again after a 10% weight loss followed by ≥4 weeks of weight maintenance, and was compared with that of eight age-matched healthy lean men (BMI: 24.7 ± 0.6 kg·m(-2)). Dietary intervention consisted of reduced carbohydrate and saturated fat intake and increased monounsaturated fat intake. Obese volunteers were advised to increase physical activity using pedometers to record daily activity. Postprandial triacylglycerolemia after weight loss was reduced by 27-46% (P < 0.05), and became similar to that of lean men despite persisting obesity (BMI after weight loss: 32.9 ± 1.5 kg·m(-2)). Reduction in postprandial TAG responses was inversely correlated with the decrease in postprandial insulin sensitivity index (ISI) after weight loss (r = -0.714, P = 0.047). We conclude that moderate weight loss induced by a low-carbohydrate and saturated fat diet and a slight increase in daily physical activity normalizes postprandial triacylglycerolemia in obese men, independently of acute diet-induced negative energy balance, and possibly through enhancement of insulin action.     

Dieting is more effective in reducing weight but exercise is more effective in reducing fat during the early phase of a weight-reducing program in healthy humans

This study compared the relative effectiveness of two means of energy deficit, food restriction (FR) and increased physical activity (EX), on body weight, body composition and concentrations of serum leptin, insulin, glucose, and lipids in female subjects. Thirteen adult female volunteers participated in a two-phase crossover-treatment study. Each phase involved a 9-day energy deficit period and a 5-day follow up energy repletion period. A 25% energy deficit was achieved by either FR or EX. Baseline values were established prior to phase one. Results showed that FR had greater body weight loss, but less body fat loss compared to EX. FR and EX both reduced serum leptin, insulin, total triacylglycerol, LDL-C and VLDL-C concentrations. However, only EX elevated HDL-C. These effects were reversed during follow up energy repletion. Results suggest that under iso-caloric energy deficit conditions FR is more effective in reducing body weight but EX is more effective in reducing body fat and maintaining lean body mass. EX can lead to a more desirable blood lipid profile than can FR. Thus, it is desirable to include exercise in a weight reduction program.     

Energy Provision,Tissue Utilization,and Weight Loss in Prolonged Starvation

Daily weight loss measurements in 76 fasting, obese patients (58 females, 18 males) have shown a characteristic pattern of rapid loss initially (up to day 14) followed by a slower but uniform reduction in weight. There were significant sex differences. Measurements of tissue breakdown showed that the initial rapid weight loss was due to the continuing utilization by the nervous system of glucose derived from lean tissue. This requirement fell noticeably from the second week of starvation. Irreversible fluid elimination also contributed to the initial phase of rapid weight loss. Fat remained the primary source of energy throughout starvation and in established fasting (more than 14 days) contributed 96% of that requirement.     

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.     

Distinct skeletal muscle fiber characteristics and gene expression in diet-sensitive versus diet-resistant obesity

Inter-individual variability in weight gain and loss under energy surfeit and deficit conditions, respectively, are well recognized but poorly understood phenomena. We documented weight loss variability in an intensively supervised clinical weight loss program and assessed skeletal muscle gene expression and phenotypic characteristics related to variable response to a 900 kcal regimen. Matched pairs of healthy, diet-compliant, obese diet-sensitive (ODS) and diet-resistant (ODR) subjects were defined as those in the highest and lowest quintiles for weight loss rate. Physical activity energy expenditure was minimal and comparable. Following program completion and weight stabilization, skeletal muscle biopsies were obtained. Gene expression analysis of rectus femoris and vastus lateralis indicated upregulation of genes and gene sets involved in oxidative phosphorylation and glucose and fatty acid metabolism in ODS compared with ODR. In vastus lateralis, there was a higher proportion of oxidative (type I) fibers in ODS compared with ODR women and lean controls, fiber hypertrophy in ODS compared with ODR women and lean controls, and lower succinate dehydrogenase in oxidative and oxidative-glycolytic fibers in all obese compared with lean subjects. Intramuscular lipid content was generally higher in obese versus lean, and specifically higher in ODS vs. lean women. Altogether, our findings demonstrate differences in muscle gene expression and fiber composition related to clinical weight loss success.     

Hormonal and psychobehavioral predictors of weight loss in response to a short-term weight reduction program in obese women

Among the factors influencing weight loss and maintenance, psychobehavioral, nutritional, metabolic, hormonal and hereditary predictors play an important role. Psychobehavioral factors influence adherence to lifestyle changes and thus weight loss maintenance. The outcome of short-term weight reduction treatment is mainly affected by changes in energy and nutrient intake and physical activity and thus the impact of hormones can possibly be obscured. In order to reveal hormonal determinants of weight loss, a 4-week in-patient comprehensive weight reduction program was introduced in which food intake and physical activity were under the strict control. Women (n = 67, BMI: 32.4+/-4.4 kg; age: 48.7+/-12.2 years) who exhibited stable weight on a 7 MJ/day diet during the first week of weight management were given a hypocaloric diet yielding daily energy deficit 2.5 MJ over the subsequent 3-week period. This treatment resulted in a mean weight loss of 3.80+/-1.64 kg. Correlation analysis revealed that baseline concentrations of several hormones were significantly associated either with a higher (free triiodothyronine, C-peptide, growth hormone, pancreatic polypeptide) or with a lower (insulin-like growth factor-I, cortisol, adiponectin, neuropeptide Y) reduction of anthropometric parameters in response to weight management. In a backward stepwise regression model age, initial BMI together with baseline levels of growth hormone, peptide YY, neuropetide Y and C-reactive protein predicted 49.8 % of the variability in weight loss. Psychobehavioral factors (items of the Eating Inventory, Beck Depression score) did not contribute to weight change induced by a well-controlled short-term weight reduction program.     

Identification of quantitative trait loci influencing traits related to energy balance in selection and inbred lines of mice.

Energy balance is a complex trait with relevance to the study of human obesity and maintenance energy requirements of livestock. The objective of this study was to identify, using unique mouse models, quantitative trait loci (QTL) influencing traits that contribute to variation in energy balance. Two F2 resource populations were created from lines of mice differing in heat loss measured by direct calorimetry as an indicator of energy expenditure. The HB F2 resource population originated from a cross between a noninbred line selected for high heat loss and an inbred line with low heat loss. Evidence for significant QTL influencing heat loss was found on chromosomes 1, 2, 3, and 7. Significant QTL influencing body weight and percentage gonadal fat, brown fat, liver, and heart were also identified. The LH F2 resource population originated from noninbred lines of mice that had undergone divergent selection for heat loss. Chromosomes 1 and 3 were evaluated. The QTL for heat loss identified on chromosome 1 in the HB population was confirmed in the LH population, although the effect was smaller. The presence of a QTL influencing 6-wk weight was also confirmed. Suggestive evidence for additional QTL influencing heat loss, percentage subcutaneous fat, and percentage heart was found for chromosome 1.