Plasma adiponectin levels are not associated with fat oxidation in humans

OBJECTIVE: To test the hypothesis that low adiponectin is associated with low fat oxidation in humans. RESEARCH METHODS AND PROCEDURES: We measured plasma adiponectin concentrations in 75 healthy, nondiabetic Pima Indians (age, 28 +/- 7 years; 55 men and 20 women; body fat, 29.7 +/- 7.5%) and 18 whites [(age, 33 +/- 8 years; 14 men and 4 women; body fat, 28.2 +/- 10.8% (means +/- SD)] whose body composition was measured by DXA and 24-hour energy expenditure (24-hour EE) by a respiratory chamber. Respiratory quotient (an estimate of whole-body carbohydrate/lipid oxidation rate) was calculated over 24 hours (24-hour RQ). RESULTS: Before correlational analyses, waist-to-thigh ratio (WTR) and percentage of body fat (PFAT) were adjusted for age, sex, and race; 24-hour EE was adjusted for fat mass and fat-free mass, and 24-hour RQ were adjusted for energy balance. Plasma adiponectin concentrations were negatively correlated with WTR (r = -0.42, p < 0.0001) and PFAT (r = -0.46, p < 0.0001). There was no correlation between plasma adiponectin concentrations and 24-hour RQ, (r = 0.09, p = 0.36) before or after adjustment for PFAT (r = 0.001, p = 0.99, respectively, partial correlation), and no correlation was found between plasma adiponectin concentrations and 24-hour EE (r = -0.12, p = 0.27). DISCUSSION: Our cross-sectional data do not suggest physiological concentrations of fasting plasma adiponectin play a role in the regulation of whole-body fat oxidation or energy expenditure in resting conditions. Whether administration of adiponectin to individuals with low levels of this hormone will increase their fat oxidation rates/energy expenditure remains to be established.     

Plasma concentrations of free triiodothyronine predict weight change in euthyroid persons

BACKGROUND: Factors that influence energy metabolism and substrate oxidation, such as thyroid hormones (THs), may be important regulators of body weight. OBJECTIVE: We investigated associations of THs cross-sectionally with obesity, energy expenditure, and substrate oxidation and prospectively with weight change. DESIGN: Euthyroid, nondiabetic, healthy, adult Pima Indians (n = 89; 47 M, 42 F) were studied. Percentage body fat (%BF) was measured by using dual-energy X-ray absorptiometry; sleeping metabolic rate (SMR), respiratory quotient, and substrate oxidation rates were measured in a respiratory chamber. Thyroid-stimulating hormone (TSH), free thyroxine (T(4)), free triiodothyronine (T(3)), and leptin concentrations were measured in fasting plasma samples. RESULTS: TSH, but neither free T(3) nor free T(4), was associated with %BF and leptin concentrations (r = 0.27 and 0.29, respectively; both: P 相似文献   

Body fat distribution and energy metabolism in obese men and women.

Upper body obesity seems to be associated with a better prognosis for weight loss than does lower body obesity. However, the impact of body fat distribution on energy metabolism is not clear.

One hundred fifteen non-diabetic obese Caucasians (64 males and 51 females) and 108 Caucasian lean controls (82 males and 26 females) were studied.

Body composition was assessed by hydrodensitometry and body fat distribution was estimated by the waist-to-thigh circumference ratio (W/T). Values of 24-hour energy expenditure (24h-EE), basal metabolic rate (BMR), sleeping metabolic rate (SMR) and respiratory quotient (RQ) were measured in a respiration chamber.

BMR, adjusted for differences in fat-free mass, fat mass, age and sex, correlated with W/T in obese males (r = 0.40; p < 0.01), but not in obese females. Obese male subjects with upper body obesity had BMR significantly higher than those with lower body obesity (2189 +/? 268 vs 1974 +/? 141 kcal/day; p < 0.01), independently of differences in fat-free mass, fat mass and age. No correlations were found between W/T and adjusted 24h-EE, SMR or RQ in all examined groups.

These findings indicate that in obese males, upper body obesity is associated with increased metabolic rate, possibly related to higher levels of lipid turnover in visceral fat.     

Energy intake and physical activity in Pima Indians: comparison with energy expenditure measured by doubly-labeled water

To test the validity of survey techniques for measuring diet and activity patterns of Pima Indians, sequential 24-hour recalls, a food frequency questionnaire (FFQ), and an activity questionnaire were compared to free-living energy expenditure. Total energy expenditure (TEE) measured by doubly labeled water was 13.27 +/- 2.95 MJ/d for the 12 males (mean +/- SD: 35 +/- 14 yr; 97 +/- 35 kg; 32 +/- 9% body fat) and 11.67 +/- 1.85 MJ/d for the 9 females (31 +/- 13 yr; 106 +/- 32 kg; 49 +/- 6% body fat). Energy intake assessed by 24-hour recall was 13.59 +/- 7.81 MJ/d for men and 9.29 +/- 2.77 MJ/d for women, compared to 12.84 + 2.85 and 9.40 + 2.61 MJ/d for men and women, respectively, by FFQ. Both dietary methods indicated significant underreporting by women when compared to TEE. Energy intake assessed by FFQ was significantly correlated with TEE (r=0.48, p=0.03). This was true with 24-hour recall energy intake only when data from two extremely large alcohol consumers were eliminated (r=0.64, p=0.03, N=19). Although a low level of activity was apparent, the activity questionnaire produced significant correlations with measurements of energy expenditure and therefore represents an important tool for examining the relationship between physical activity and diseases.     

Lack of relationship between calcium intake and body size in an obesity-prone population

OBJECTIVE: Dietary calcium intake, especially from dairy products, may have a protective effect against obesity. This study aimed to determine if calcium intake is associated with body weight and adiposity in Pima Indians, an obesity-prone population. RESEARCH METHODS AND PROCEDURES: Subjects were 65 Pima Indian adults (35 men/30 women, age 33+/-8 years [mean+/-standard deviation]) participating in a study of eating behavior and 78 Pima Indian children (36 boys/42 girls, age 10.4+/-0.3 years) participating in a study of childhood obesity. Height and weight were measured, and body composition was determined by dual-energy x-ray absorptiometry. Food intake in adults was assessed using the Block 1998 Food Questionnaire; food intake in children was assessed using a 24-hour recall with parental assistance. RESULTS: In adults, mean energy intake was 3,163+/-1,037 kcal/day, mean percentage of energy from fat was 41%+/-7%, and calcium intake was 914+/-333 mg/day. In children, mean energy intake was 1,988+/-733 kcal/day, mean percentage of energy from fat was 36%+/-9%, and calcium intake was 637+/-352 mg/day, half the recommended daily intake for this age group. There were no significant associations between calcium intake and body weight (r=0.05, P=.71; r=0.04, P=.73), body fat (r=0.16, P=.19; r=0.12, P=.42), or body mass index (r=0.01, P=.97; r=0.04, P=.77) in either adults or children, respectively. DISCUSSION: One explanation for the lack of association between reported calcium intake and body size in Pima Indians may be that the high-fat, high-energy diet consumed by the population overwhelmed the "anti-obesigenic" effect of calcium. CONCLUSIONS: We were unable to find an association between calcium intake and body size or adiposity in Pima Indian adults and children. Although the essentiality of calcium to bone health is well established, the role of calcium and dairy product intake in obesity and weight management remains uncertain.     

Birth weight, weight at 1 y of age, and body composition in older men: findings from the Hertfordshire Cohort Study

BACKGROUND: Size in early life is related to adult body mass index, and early environmental influences have been proposed to have lifelong consequences for obesity. However, body mass index also reflects fat-free mass, and few studies have examined the relation between size in early life and direct measures of body composition in older people. OBJECTIVE: We investigated the associations of birth weight and weight at 1 y of age with body composition in older men. DESIGN: We carried out a retrospective cohort study in Hertfordshire, United Kingdom. Men who were born between 1931 and 1939 and for whom there were records of birth weight and weight at 1 y of age (n = 737) participated in the study. The main outcome measures were adult body mass index, fat-free mass, and fat mass. RESULTS: Birth weight was significantly and consistently positively associated with adult body mass index and fat-free mass but not with measures of adult fat mass. In contrast, weight at 1 y of age was associated with adult body mass index, fat-free mass, and fat mass. CONCLUSIONS: The consistently reported positive relation between birth weight and adult body mass index may reflect prenatal and maternal influences on fat-free mass rather than on fat mass in older people. The postnatal environment may be more influential than prenatal factors in the development of obesity in later life.     

Relation between energy expenditure and body composition in man: specific energy expenditure in vivo of fat and fat-free tissue

The relationship between energy expenditure and body composition, in terms of fat and fat-free masses, has previously been described by a variety of predictive regression equations with parameters devoid of physiological content. We present here results obtained by calculating the specific energy expenditure, ie, the energy expenditure per unit of mass, of fat and fat-free tissue on the basis of measurements of the total energy expenditure (EE), the masses of fat (FM), and fat-free (FFM) tissue using the following simple model: EE = k1.FM + k2.FFM where k1 and k2 are the specific energy expenditures of fat and fat-free tissue, respectively. The results of observations on 104 women at rest yielded values for k1 and k2 of 0.31 and 1.35 watts/kg of fat and fat-free mass, respectively, with standard errors of estimate of 0.074 and 0.052 watts/kg, respectively. Analysis of several series of measurements, from other sources and on smaller samples of subjects, yielded similar values at rest but with larger standard errors of estimate. Data from subjects performing varying amounts of work in 24-h measurements showed, as expected, larger values for both tissues. The results explain to a very large extent the well-established relation between resting metabolic rate and body weight, ie, a linear relation with a non-zero intercept. The results also offer a clear-cut explanation for the well known difference in energy expenditure between men and women with the same body weight.     

Sedentary daily expenditure: a base for estimating individual energy requirements

As a base for estimating individual energy requirements, we propose using the energy expenditure of a sedentary day with regular meals and sleep at night. Ninety-five 24-h measurements of sedentary daily expenditure (SDE) by direct calorimetry on 37 men and women were analyzed, showing that fat-free mass combined with body mass index correlated highly with SDE (r2 = 0.92) with an SE of 5%. Weight and fat mass were better predictors for women and excellent predictors for men. We found that weight and height accurately predicted fat mass if suitable exponents were used in the expression wt/htx. Testing predictive equations with our own and other sets of data showed good agreement between estimated and observed SDEs. As a base for estimating individual energy requirements. SDE is more precise than basal metabolic rate and it can be predicted with useful accuracy from simple measures of weight and height.     

Aging and energy expenditure

Whether sedentary energy expenditure is normal or lower in elderly people has not yet been clearly established. Twenty-four-hour energy expenditure (24EE) and its different components were measured by use of a respiratory chamber in elderly (17 male, 21 female; 71 +/- 6 y, mean +/- SD; 71.2 +/- 13.5 kg; 32 +/- 8% fat) and young (33 male, 31 female; 24 +/- 4 y; 84.5 +/- 23.1 kg; 25 +/- 13% fat) subjects. The elderly subjects had lower mean height (P less than 0.001), weight (P less than 0.01), and fat-free mass (P less than 0.001) but higher percent body fat (P less than 0.01) than did the young adults. Absolute 24EE, basal metabolic rate (BMR), and sleeping metabolic rate were significantly lower (P less than 0.01) in the elderly subjects than in the young subjects. However, after differences in fat-free mass, fat mass, and sex were adjusted for, only BMR was found to be lower in the elderly subjects (P less than 0.01). Despite a reduced adjusted BMR in older subjects, sedentary 24EE was decreased only in proportion to their reduced body size, suggesting that the lower energy intake reported in elderly people might be mainly related to lower physical activity in free-living conditions.     

Comprehensive assessment of the components of energy expenditure in infants using a new infant respiratory chamber.

BACKGROUND: Current methods for energy expenditure (EE) measurements in term infants do not include simultaneous measurements of basal and sleeping metabolic rates (BMR and SMR) or a measure of physical activity (PA). Furthermore, prediction equations for calculating EE are not appropriate for use in infants with metabolic disorders. OBJECTIVE: To develop and utilize a new infant respiratory chamber for simultaneous measurements of EE (kJ/d), preprandial BMR (kJ/d), SMR (kJ/d) and an index of PA (oscillations/min/kg body weight) in infants with a variety of metabolic disorders, for up to four hours in a hospital setting, while allowing parental interaction in a comfortable environment. METHODS: We obtained simultaneous measurements of EE, BMR, SMR and PA in 21 infants (66+/-73 days of age, 4.5+/-1.7 kg body weight, 55+/-8 cm in length and 16+/-7% body fat) using our new infant respiratory chamber. Six of these infants were healthy, seven had thyroid dysfunction, five were HIV-exposed, one had AIDS, one had intrauterine and postnatal growth retardation and one was a hypothermic preterm infant. Energy expenditure, BMR and SMR were extrapolated for 24 hours. Body composition was estimated by skin-fold thickness, using age-appropriate formulae. Basal metabolic rate obtained with the infant respiratory chamber was compared to BMR that was calculated using the appropriate World Health Organization (WHO) equations. RESULTS: In all infants both extrapolated 24-hour EE and BMR correlated with fat-free mass (r = 0.89, p<0.01 and r = 0.88, p<0.01 respectively). Twenty-four hour EE also correlated with PA (r = 0.52, p<0.05). The HIV-exposed infants had higher BMR (p<0.05) than that calculated by the appropriate WHO equation. We found that the caloric requirements for the infant with growth retardation were underestimated based on the infant's weight and age. CONCLUSIONS: The infant respiratory chamber can measure all of the main components of EE. Some of the results obtained differed significantly from those obtained by the WHO equations; therefore, the new infant respiratory chamber is necessary for estimating EE in infants with metabolic and growth disorders.     

Leptin levels are associated with fat oxidation and dietary-induced weight loss in obesity

OBJECTIVE: To examine the relationship between fasting plasma leptin and 24-hour energy expenditure (EE), substrate oxidation, and spontaneous physical activity (SPA) in obese subjects before and after a major weight reduction compared with normal weight controls. To test fasting plasma leptin, substrate oxidations, and SPA as predictive markers of success during a standardized weight loss intervention. RESEARCH METHODS AND PROCEDURES: Twenty-one nondiabetic obese (body mass index: 33.9 to 43.8 kg/m(2)) and 13 lean (body mass index: 20.4 to 24.7 kg/m(2)) men matched for age and height were included in the study. All obese subjects were reexamined after a mean weight loss of 19.2 kg (95% confidence interval: 15.1-23.4 kg) achieved by 16 weeks of dietary intervention followed by 8 weeks of weight stability. Twenty-four-hour EE and substrate oxidations were measured by whole-body indirect calorimetry. SPA was assessed by microwave radar. RESULTS: In lean subjects, leptin adjusted for fat mass (FM) was correlated to 24-hour EE before (r = -0.56, p < 0.05) but not after adjustment for fat free mass. In obese subjects, leptin correlated inversely with 24-hour and resting nonprotein respiratory quotient (r = -0.47, p < 0.05 and r = -0.50, p < 0.05) both before and after adjustments for energy balance. Baseline plasma leptin concentration, adjusted for differences in FM, was inversely related to the size of weight loss after 8 weeks (r = -0.41, p = 0.07), 16 weeks (r = -0.51, p < 0.05), and 24 weeks (r = -0.50, p < 0.05). DISCUSSION: The present study suggests that leptin may have a stimulating effect on fat oxidation in obese subjects. A low leptin level for a given FM was associated with a greater weight loss, suggesting that obese subjects with greater leptin sensitivities are more successful in reducing weight.     

Energy balance in children and young adultsreceiving haernodialysis for chronic renal failure

This study was designed to determine the contribution of energy expenditure tothe energy imbalance seen in uraemic children. Resting energy expenditure (REE) was measured using open-circuit indirect calorimetry in eight uraemic haemodialysed subjects aged 9.3–20.4 years and in 10 healthy children. Linear correlations between REE and both body weight and fat-free mass as measured by anthropometry were found in both controls and uraemic subjects (respectively: r = 0.76 and r = 0.88 for body weight and r = 0.73 and r = 0.90 for fat-free mass). Measured REE in uraemic patients was not different from the value predicted by using actual body weight and fat-free mass in the regression equation of REE on body weight and fat-free mass in controls (paired t test: p = 0.70 and p = 0.19 respectively). These data suggest that the energy imbalance seen in uraemic children is not due to increased energy expenditure and is therefore probably due to decreased food intake.     

Energy balance in children and young adults receiving haemodialysis for chronic renal failure

This study was designed to determine the contribution of energy expenditure to the energy imbalance seen in uraemic children. Resting energy expenditure (REE) was measured using open-circuit indirect calorimetry in eight uraemic haemodialysed subjects aged 9.3-20.4 years and in 10 healthy children. Linear correlations between REE and both body weight and fat-free mass as measured by anthropometry were found in both controls and uraemic subjects (respectively: r = 0.76 and r = 0.88 for body weight and r = 0.73 and r = 0.90 for fat-free mass). Measured REE in uraemic patients was not different from the value predicted by using actual body weight and fat-free mass in the regression equation of REE on body weight and fat-free mass in controls (paired t test: p = 0.70 and p = 0.19 respectively). These data suggest that the energy imbalance seen in uraemic children is not due to increased energy expenditure and is therefore probably due to decreased food intake.     

Skeletal muscle enzymes as predictors of 24-h energy metabolism in reduced-obese persons

BACKGROUND: Little is known about the effects of weight loss on the relation between skeletal muscle enzymes and energy metabolism. OBJECTIVE: This study was performed retrospectively to investigate the relation between skeletal muscle enzymes and 24-h energy metabolism in obese persons before and after weight loss. DESIGN: Ten women and 9 men [with body mass indexes (in kg/m(2)) > 30] underwent a 15-wk weight-loss program (-700 kcal/d). Body weight and composition, 24-h energy metabolism (whole-body indirect calorimetry), and maximal activities of phosphofructokinase (EC 2.7.1.11), creatine kinase (CK; EC 2.7.3.2), citrate synthase (CS; EC 4.1.3.7), 3-hydroxyacyl-CoA dehydrogenase (HADH; EC 1.1.1.35), and cytochrome-c oxidase (COX; EC 1.9.3.1) were determined from biopsy samples of the vastus lateralis taken before and after weight loss. RESULTS: Before weight loss, fat-free mass (FFM) was the only predictor of 24-h energy expenditure (R(2) = 0.70, P < 0.001), whereas the cumulative variance in sleeping metabolic rate explained by FFM and fat mass (FM) was 83% (P < 0.001). After weight loss, CS (r = 0.45, P = 0.05) and COX (r = 0.65, P < 0.01) were significantly associated with 24-h energy expenditure, whereas CK (r = 0.53, P < 0.05), CS (r = 0.45, P < 0.05), COX (r = 0.64, P < 0.01), and HADH (r = 0.45, P = 0.05) were all significant correlates of sleeping metabolic rate. After weight loss, FFM, FM, and COX explained 84% (P < 0.01) of the variance in 24-h energy expenditure, whereas FFM, FM, and CK all contributed to the cumulative variance in sleeping metabolic rate explained by this model (R(2) = 0.82, P < 0.05). CONCLUSION: Maximal activities of key skeletal muscle enzymes contribute to the variability in 24-h energy metabolism in reduced-obese persons.     

Growth, thermogenesis, and hyperphagia

Resting metabolic rate is demonstrated to be a function of fat-free mass and a growth variable related to food-energy-input imbalance rate. By use of obligatory energy expenditure terms, the two-reservoir energy model applied to hyperphagia shows that growth of the fat-free mass is rapid whereas that of the fat store is slow and that the growth of both is bounded. Most of the excess energy at the onset of hyperphagia initially goes into the fat store, but this decreases with time until the greater fraction is diverted to the fat-free mass. The two-reservoir model predicts that weight gain per unit of excess energy is not constant but decreases monotonically until ultimately reaching an asymptotic value. Departure of theory and experiment in the long term suggests that facultative considerations become increasingly important.     

Taste preferences and body weight changes in an obesity-prone population

BACKGROUND: Taste preferences for highly palatable foods rich in sugar and fat may underlie the current epidemic of obesity. OBJECTIVE: This study aimed to determine whether the hedonic response to sweet and creamy solutions differs between whites and Pima Indians and whether a preference for these tastes predicts weight gain. DESIGN: One hundred twenty-three Pima Indian and 64 white volunteers taste tested solutions of nonfat milk (0.1% fat), whole milk (3.5% fat), half and half (11.3% fat), and cream (37.5% fat) containing 0%, 5%, 10%, or 20% sugar by weight. Solutions were rated for perceived sweetness, creaminess, and pleasantness (hedonic response) on a 100-mm visual analogue scale. Follow-up body weight was measured in 75 Pima Indians 5.5 +/- 3.0 y ( +/- SD) after baseline taste testing. RESULTS: The Pima Indians had a significantly (P = 0.006) lower hedonic response than did the whites (repeated-measures analysis of variance). Neither body size (P = 0.56) nor adiposity (P = 0.86) was a significant predictor of the hedonic response. There was a positive correlation (r = 0.28, P = 0.01) between the maximal hedonic response at baseline and subsequent weight gain in the Pima Indians. CONCLUSION: Although the Pima Indians liked sweet and creamy solutions less than the whites did, a heightened hedonic response for these solutions among the Pima Indians was associated with weight gain.     

Resting energy expenditure and substrate utilisation rate in children with constitutional leanness or obesity

BACKGROUND & AIM: The influence of energy expenditure on body weight regulation, in the absence of organic disease, has never been studied in a paediatric population covering a broad range of body weights. The aim of this study was to investigate resting energy metabolism in children with constitutional leanness, normal body weight, or common obesity. METHODS: Fourteen children with constitutional leanness, 16 children with obesity, and controls were studied. Resting energy expenditure and postabsorptive substrate utilisation rate were measured by indirect calorimetry and body composition was assessed from skinfold thicknesses. RESULTS: As compared to the predicted value calculated from the regression equation of resting energy expenditure on fat-free mass in the controls, resting energy expenditure was decreased in lean children (P=0.002), whereas no difference was found in obese children. In obese children and the overall population, fat mass was positively correlated with fat oxidation rate. In each group and in the overall population, fat oxidation rate was positively correlated to resting energy expenditure. CONCLUSIONS: Constitutionally lean children have a low resting metabolic rate, probably adaptive in nature. In obese children, resting energy expenditure is increased in proportion to the fat-free mass, and fat balance is the main determinant of energy balance. These data suggest a constitutional regulation of body weight.     

Energy requirements derived from total energy expenditure and energy deposition during the first 2 y of life

BACKGROUND: Current recommendations for energy intake of children are derived from observed intakes. Deriving energy requirements on the basis of energy expenditure and deposition is scientifically more rational than is using the observational approach and is now possible with data on total energy expenditure (TEE), growth, and body composition. OBJECTIVES: The objectives of this study were 1) to define energy requirements during the first 2 y of life on the basis of TEE and energy deposition; 2) to test effects of sex, age, and feeding mode on energy requirements; and 3) to determine physical activity. DESIGN: TEE, sleeping metabolic rate, anthropometry, and body composition were measured in 76 infants. TEE was measured with doubly labeled water, sleeping metabolic rate with respiratory calorimetry, and body composition with a multicomponent model. RESULTS: Total energy requirements were 2.23, 2.59, 2.97, 3. 38, 3.72, and 4.15 MJ/d at 3, 6, 9, 12, 18, and 24 mo, respectively. Energy deposition (in MJ/d) decreased significantly over time (P: = 0.001) and was lower in breast-fed than in formula-fed infants (P: = 0.01). Energy requirements were approximately 80% of current recommendations. Energy requirements differed by age (P: = 0.001), feeding group (P: = 0.03), and sex (P: = 0.03). Adjusted for weight or fat-free mass and fat mass, energy requirements still differed by feeding group but not by age or sex. Temperament and motor development did not affect TEE. CONCLUSION: The TEE and energy-deposition data of these healthy, thriving children provide strong evidence that current recommendations for energy intake in the first 2 y of life should be revised.     

Low resting and sleeping energy expenditure and fat use do not contribute to obesity in women

OBJECTIVE: Determine whether sleeping and resting energy expenditure and sleeping, resting, and 24-hour fuel use distinguish obesity-prone from obesity-resistant women and whether these metabolic factors explain long-term weight gain. RESEARCH METHODS AND PROCEDURES: Forty-nine previously overweight but currently normal-weight women were compared with 49 never-overweight controls. To date, 87% of the 98 women have been re-evaluated after 1 year of follow-up, without intervention, and 38% after 2 years. Subjects were studied at a General Clinical Research Center after 4 weeks of tightly controlled conditions of energy balance and macronutrient intake. Forty-nine obesity-prone weight-reduced women were group-matched with 49 never-overweight obesity-resistant controls. All were premenopausal, sedentary, and normoglycemic. Energy expenditure and fuel use were assessed using chamber calorimetry. Body composition was assessed using DXA. RESULTS: At baseline, percent body fat was not different between the obesity-prone and control women (33 +/- 4% vs. 32 +/- 5%, respectively; p = 0.22). Analysis of covariance results show that after adjusting for lean and fat mass, sleeping and resting energy expenditure of obesity-prone women was within 2% of controls. Neither sleeping nor resting energy expenditure nor sleeping, resting, or 24-hour fuel use was significantly different between the groups (p > 0.25). None of the metabolic variables contributed significantly to patterns of weight gain at 1 or 2 years of follow-up. DISCUSSION: The results suggest that when resting and sleeping energy expenditure and fuel use are assessed under tightly controlled conditions, these metabolic factors do not distinguish obesity-prone from obesity-resistant women or explain long-term weight changes.