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Background: The daily energy imbalance gap associated with the current population weight gain in the obesity epidemic is relatively small. However, the substantially higher body weights of populations that have accumulated over several years are associated with a substantially higher total energy expenditure (TEE) and total energy intake (TEI), or energy flux (EnFlux = TEE = TEI). Objective: The objective was to develop an equation relating EnFlux to body weight in adults for estimating the rise in EnFlux associated with the obesity epidemic. Design: Multicenter, cross-sectional data for TEE from doubly labeled water studies in 1399 adults aged 5.9 [+ or -] 18.8 y (mean [+ or -] SD) were analyzed in linear regression models with natural log (In) weight as the dependent variable and In EnFlux as the independent variable, adjusted for height, age, and sex. These equations were compared with those for children and applied to population trends in weight gain. Results: In EnFlux was positively related to In weight ([beta] = 0.71; 95% CI: 0.66, 0.76; [R.sup.2] = 0.52), adjusted for height, age, and sex. This slope was significantly steeper than that previously described for children ([beta] = 0.45; 95% CI: 0.38, 0.51). Conclusions: This relation suggests that substantial increases in TEI have driven the increases in body weight over the past 3 decades. Adults have a higher proportional weight gain than children for the same proportional increase in energy intake, mostly because of a higher fat content of the weight being gained. The obesity epidemic will not be reversed without large reductions in energy intake, increases in physical activity, or both.

Background: We tested the hypothesis that ad libitum food intake shows corrective responses over periods of 1-5 d. Design: This was a prospective study of food intake in women. Methods: Two methods, a weighed food intake and a measured food intake, were used to determine daily nutrient intake during 2 wk in 20 women. Energy expenditure with the use of doubly labeled water was done contemporaneously with the weighed food-intake record. The daily deviations in macronutrient and energy intake from the average 7-d values were compared with the deviations observed 1, 2, 3, 4, and 5 d later to estimate the corrective responses. Results: Both methods of recording food intake gave similar patterns of macronutrient and total energy intakes and for deviations from average intakes. The intraindividual CVs for energy intake ranged from [+ or -] 12% to [+ or -] 47% with an average of [+ or -] 25%. Reported energy intake was 85.5-95.0% of total energy expenditure determined by doubly labeled water. Significant corrective responses were observed in food intakes with a 3- to 4-d lag that disappeared when data were randomized within each subject. Conclusions: Human beings show corrective responses to deviations from average energy and macronutrient intakes with a lag time of 3-4 d, but not 1-2 d. This suggests that short-term studies may fail to recognize important signals of food-intake regulation that operate over several days. These corrective responses probably play a crucial role in bringing about weight stability.

Background: There remains no consensus about the optimal dietary composition for sustained weight loss. Objective: The objective was to examine the effects of 2 dietary macronutrient patterns with different glycemic loads on adherence to a prescribed regimen of calorie restriction (CR), weight and fat loss, and related variables. Design: A randomized controlled trial (RCT) of diets with a high glycemic load (HG) or a low glycemic load (LG) at 30% CR was conducted in 34 healthy overweight adults with a mean ([+ or -] SD) age of 35 [+ or -] 6 y and body mass index (kg/[m.sup.2]) of 27.6 [+ or -] 1.4. All food was provided for 6 mo in diets controlled for confounding variables, and subjects self-administered the plans for 6 additional months. Primary and secondary outcomes included energy intake measured by doubly labeled water, body weight and fatness, hunger, satiety, and resting metabolic rate. Results: All groups consumed significantly less energy during CR than at baseline (P < 0.01), but changes in energy intake, body weight, body tat, and resting metabolic rate did not differ significantly between groups. Both groups are more energy than provided (eg, 21% and 28% CR at 3 mo and 16% and 17% CR at 6 mo with HG and LG, respectively). Percentage weight change at 12 mo was -8.04 [+ or -] 4.1% in the HG group and -7.81 [+ or -] 5.0% in the LG group. There was no effect of dietary composition on changes in hunger, satiety, or satisfaction with the amount and type of provided food during CR. Conclusions: These findings provide more detailed evidence to suggest that diets differing substantially in glycemic load induce comparable long-term weight loss. KEY WORDS Glycemic load, caloric restriction, body weight, metabolism

Background: Clinical trials involving calorie restriction (CR) require an assessment of adherence to a prescribed CR with the use of an objective measure of energy intake (EI). Objective: The objective was to validate the use of energy expenditure (EE) measured by doubly labeled water (DLW), in conjunction with precise measures of body composition, to calculate an individual's EI during 30% CR. Design: Ten participants underwent 30% CR for 3 wk. During the last week (7 d), 24-h EE was measured in a respiratory chamber and simultaneously by DLW (E[E.sub.DLW]). EI was calculated from 7-d EE measured by DLW and from changes in energy stores (ES) (weight and body composition). Calculated EI was then compared with the actual EI measured in the chamber by using the following equations: calculated EI (kcal/d) = E[E.sub.DLW] + [DELTA]ES, where [DELTA]E[S.sub.FM/FFM] (kcal/d) = (9.3 x [DELTA]FM, g/d) + (1.1 x [DELTA]FFM, g/d), FM is fat mass, and FFM is fat-free mass. Results: We found close agreement (R = 0.88) between EE measured in the metabolic chamber and E[E.sub.DLW] during CR. Using the measured respiratory quotient, we found that the mean ([+ or -] SD) E[E.sub.DLW] was 1934 [+ or -] 377 kcal/d and EE measured in the metabolic chamber was 1906 [+ or -] 327 kcal/d, ie, a 1.3 [+ or -] 8.9% overestimation. EI calculated from E[E.sub.DLW] and from changes in ES was 8.7 [+ or -] 36.7% higher than the actual E1 provided during the chamber stay (1596 [+ or -] 656 kcal/d). Conclusions: DLW methods can accurately estimate 24-h EE during CR. Although the mean difference between actual and calculated EIs for the group was small, we conclude that the interindividual variability was too large to provide an assessment of CR adherence on an individual basis. KEY WORDS Doubly labeled water method, DLW, energy intake, body composition, metabolic chamber

Background: The hypothesis that alterations in energy metabolism predict body fat gain is controversial. Objective: The aim of this study was to determine which components of energy metabolism were most important in predicting fat gain in children aged 10.8 [+ or -] 0.6 y. Design: A 2-y longitudinal study to examine whether components of energy metabolism are predictors of body fat gain was conducted in 114 preadolescent African American and white children aged 9-11 y by measuring total daily energy expenditure on the basis of doubly labeled water (DLW), resting metabolic rate, the thermic effect of food, energy expended in physical activity, and substrate oxidation after a meal. The primary endpoint was the 2-y change in percentage body fat (%BF). Results: Individual variables of energy metabolism predicted up to 7% of the variance in changes in %BF over the 2-y interval in the whole group. Predictors of change in body fatness tended to be sex and race specific. Protein oxidation during a test meal explained a significant portion of the variance in change in %BF in the overall group and in nearly all of the subgroups. Multivariate prediction models accounted for 10-41% of the variance in change in %BF. Tanner stage at 2-y follow-up was highly predictive of change in body fatness and improved the overall prediction, accounting for 24-62% of the variance in change in %BF in those groups in which Tanner entered the model. Conclusion: This study provides evidence that total daily energy expenditure, resting metabolic rate, substrate oxidation, and total energy intake are predictors of gain in body fatness during late childhood in boys and girls. KEY WORDS Metabolic rate, ethnicity, boys, girls, thermic effect of food, respiratory quotient

A study aims to characterize and compare the total energy expenditure (TEE) and core temperature responses in men and women working almost continuously for 54 hours in an outdoor environment while developing a substantial energy deficit. Results show that, for both men and women, total energy expenditures (TEE) were among the highest observed for a military field training exercise (FEX), and that TEE, when normalized or corrected to body mass and fat-free mass, and physical activity level were the same for both sexes.

Background: A challenging 7-d ranger field exercise (FEX) by cadets in the Norwegian Military Academy provided a venue in which to study the effects of negative energy balance. Objective: We quantified total energy expenditure (TEE), food intake, and changes in body composition in male and female cadets. Design: TEE (measured by doubly labeled water), food intake, activity patterns (measured by accelerometry), and body composition (measured by dual-energy X-ray absorptiometry) were measured in 16 cadets (10 men and 6 women aged 21-27 y). Results: The physically active ([approximately equal to] 23 h/d) and semistarved (0.2-2.2 MJ/d) cadets lost weight (x [+ or -] SD: men, -7.7 [+ or -] 1.1 kg; women, -5.9 [+ or -] 1.1 kg; P < 0.05). Absolute TEE differed by sex (men, 26.6 [+ or ] 2.0 MJ/d; women, 21.9 [+ or -] 2.0 MJ/d; P < 0.05) but body weight-specific TEE did not (men, 343 [+ or -] 26 kJ x [kg.sup.-1] x [d.sup.-1]; women, 354 [+ or -] 18 kJ x [kg.sup.-1] x [d.sup.-l]; NS). Fat-free mass (FFM) loss differed significantly by sex (men, -4.0 [+ or -] 1.2 kg; women, -2.5 [+ or -] 1.1 kg; P < 0.05), but percentage FFM loss did not (men, -6.3 [+ or -] 1.9%; women, -5.6 [+ or -] 2.4%). In contrast, absolute FM loss did not differ significantly by sex (men, -3.45 [+ or -] 0.72 kg; women, -3.42 [+ or -] 0.22 kg), but fat oxidation (men, 5.2 [+ or -] 1.0 mg x [min.sup.-1] x kg [FFM.sup.-1]; women, 7.3 [+ or -] 0.5 mg x [min.sup.-1] x kg [FFM.sup.-1]) and the relative contribution of FM to TEE (men, 74 [+ or -] 14%; women, 89 [+ or -] 6%) were significantly greater in women than in men (P < 0.05). Conclusion: Female cadets maintained a significantly more fat-predominant fuel metabolism than did male cadets in response to sustained exercise and semistarvation. KEY WORDS Starvation, sustained exercise, body composition, sex, water intake, military rangers, Norway

Background: Accurate estimation of children's resting energy expenditure (REE) is important for planning dietary therapy. Objective: Our objective was to compare the utility of 5 REE prediction equations in a diverse sample of young children. Design: REE was obtained in 502 black and white girls and boys aged 6-11 y by using indirect calorimetry at 4 US sites. Measured REE and REE predicted from the equations were compared. Results: None of the equations provided both accurate and unbiased estimates of REE. Two new sets of sex-specific equations including race as a factor were generated and evaluated. One set used easily measured variables--females: REE = 0.046 x weight - 4.492 x 1/[height.sup.2] - 0.151 x race + 5.841; males: REE = 0.037 x weight - 4.67 x 1/[height.sup.2] - 0.159 x race + 6.792--and accounted for 72% and 69%, respectively, of REE variance. The other set used body-composition variables females: REE = 0.101 x fat-free mass + 0.025 x fat mass + 0.293 x [height.sup.3] - 0.185 x race + 1.643; males: REE = 0.078 x fat-free mass + 0.026 x fat mass - 2.646 x 1/height: - 0.244 x race + 4.8--and accounted for 75% and 71%, respectively, of REE variance. When split by race and adiposity, the small bias generated could be corrected to within 0.25 MJ (60 kcal) of the mean measured value. Conclusion: Sex-specific equations must take race into account to predict REE adequately in children. KEY WORDS Child, prediction equation, energy expenditure, metabolic rate, race, obesity

Background: Previously reported race and sex differences in energy expenditure (EE) may play a role in body fat gain. Objective: The purpose of the study was to determine the relations between race, sex, Tanner stage, and EE. Design: We conducted a 2-y follow-up study of EE in 114 African American (AA) and white girls and boys aged 12.7 [- or +] 0.1 y ([bar]x [+ or -] SE), who were stratified as obese or lean and were part of the Baton Rouge Children's Study. Total daily EE (TDEE) was measured by using doubly labeled water. Resting metabolic rate (RMR) and thermic effect of food were measured by using indirect calorimetry. Results: White children had significantly higher TDEE and RMR than did AA children when fat-free mass was considered. Boys had significantly higher TDEE and RMR than did girls, even after adjustment for differences in size. TDEE and RMR were significantly higher in obese children, as a result of their greater fat-free mass and body fat, than in lean children. Activity-related EE did not differ significantly between obese and lean children. There was a strong relation between initial and 2-y TDEE and RMR. There was a significant decrease in activity-related EE in both racial groups. AA children had significantly more lean limb mass than did white children. Conclusions: Average TDEE did not change over 2 y, but RMR increased significantly, and activity-related EE decreased significantly. Differences in trunk and limb lean mass of white and AA children may explain some of the ethnic differences in EE. The decrease in physical activity over 2 y may contribute to the risk of obesity. KEY WORDS Resting metabolic rate, thermic effect of food, doubly labeled water, total daily energy expenditure, physical activity, obesity, children, lean mass distribution, Baton Rouge Children's Study

Background: The prevalence of obesity is increasing in children. Validation of methods of predicting fatness in African American and white children could help to identify children at high risk. Objective: We assessed published methods for determining body fat in 12-y-old male and female white and African American schoolchildren. Design: The body fat of 114 children was measured with the use of dual-energy X-ray absorptiometry, underwater weighing (densitometry), measurement of skinfold thicknesses, isotope dilution ([H.sub.2][sup.18]O), and bioelectrical impedance analysis. Formulas derived from these data and from published reports were compared by using the Bland-Altman approach. Results: Calculation of percentage of body fat by using an equation predicting body fat in kg and dividing by the current weight was the criterion method against which the other methods were compared. Four-compartment models had the smallest variability across the range of body fat, and 2 of these models differed from the criterion method by 1-2%. Six methods (the Pennington 4-compartment model, the Wells et al 4-compartment model, the isotope dilution model, dual-energy X-ray absorptiometry, the Pennington skinfold thickness model, and the Pennington density model) provided specificity > 90%, an estimate of body fat that was within the 95% CI of the criterion method, and a difference from the criterion method that was < [+ or -] 2%. Bioelectrical impedance analysis was the least acceptable method. Conclusions: A 4-compartment model in which body fat in kg is divided by current body weight and multiplied by 100 provides the best estimate of percentage of body fat. The isotope dilution and body density models provide estimates within 2% of the estimate provided by the 4-compartment model. Other models do less well. KEY WORDS Dual-energy X-ray absorptiometry, bioelectrical impedance analysis, skinfold thickness, densitometry, isotope dilution, 4-compartment models, body fat, children, whites, African Americans

Background: Low energy expenditure has been identified as a potential risk factor for body fat gain. Objective: The objective was to determine the relations between race, sex, body fat, and energy expenditure. Design: As part of the Baton Rouge Children's Study, energy expenditure was examined in 131 preadolescent African American and white girls and boys, further stratified as obese or lean. Total daily energy expenditure (TDEE) was measured by the doubly labeled water method. Resting metabolic rate (RMR) and the thermic effect of food were measured by indirect calorimetry. Fat-free mass and fat mass were measured by dual-energy X-ray absorptiometry. To account for differences in body size, energy expenditure variables were adjusted with the use of fat-free mass or fat-free mass and fat mass as covariates. Results: The African American children had lower TDEE and RMR than did the white children. A lower level of energy expended in physical activity by the African American girls and a lower RMR in the African American boys accounted for the racial differences in TDEE. The white boys had a higher RMR than did the white girls. The girls had a lower TDEE and expended less energy in activity than did the boys. Energy expended in activity was lower in the obese children. Conclusions: The African American children expended less energy than did the white children. The obese children spent less time engaged in activity or engaged in lower-intensity activity. Obese children may maintain their obese state by spending less time in physical activity, but they do not have a reduced RMR or thermic effect of food. Am J Clin Nutr 2002;75:705-13. KEY WORDS Resting metabolic rate, thermic effect of food, doubly labeled water, total daily energy expenditure, physical activity, obesity, children, Baton Rouge Children's Study

The role that energy expenditure plays in pediatric obesity was somewhat confused by early research purporting to show that, as a group, obese children have lower energy intakes than do lean children. On the basis of this intake data, the conclusion was drawn that obese persons are somehow energy efficient, leading to weight gain. More recent research examining energy expenditure has shown clearly that, as a group, obese children have higher energy expenditures than do their lean counterparts. With the advent of the doubly labeled water method for determining free-living energy expenditure, it has been shown that obese children underreport intake significantly more than do lean children. When measurements are properly adjusted for differences in body size, there are generally no major differences in energy expenditure between lean and obese groups. However, in some cross-sectional studies, a low level of physical activity has been shown to be related to current body fatness. In addition, longitudinal studies have shown that a low level of energy expenditure, particularly energy expended in physical activity, is associated with both body fatness and weight gain. Am J Clin Nutr 1998; 68(suppl):950S-5S.

It has been suggested that fish oils, in the form of supplements or fish itself, may alter the levels of lipids (fats) in the blood in a beneficial way. However, studies evaluating the effects of fish oils on blood cholesterol and triglycerides have yielded conflicting results. The most frequently reported effect of fish oils has been a reduction in blood triglycerides. Total cholesterol has not been altered by fish oil consumption in most studies, however, a few studies have reported decreases in cholesterol levels. The effects of fish oils on high-density-lipoprotein (HDL) cholesterol, the type of cholesterol that may protect against heart disease, have been very inconsistent; fish oils have been associated with increases, decreases, and no change in HDL cholesterol. Some of the disagreement between studies might be due to the common practice of allowing subjects to consume their usual diets while taking fish oils. This introduces error into a study because daily variations in an individual's diet can alter or mask the effect of the supplement. In the current study, this problem was averted by feeding 15 healthy male college students a controlled diet. For five weeks, three groups of five students each took no fish oil, 5 grams (g) fish oil per day, or 20 g fish oil per day; the groups that consumed fish oil took it in place of an equal amount of margarine. Blood tests revealed that both doses of fish oil led to changes in the fatty acid composition of the blood and blood cells, as the n-3 fatty acids (found in fish oils) were incorporated into these cells. In addition, the group taking 20 g of fish oil experienced a 30 percent decrease in triglycerides after two weeks of taking the supplements, with no additional decrease during the next three weeks. The lower dose of fish oils had no effect upon triglycerides, and neither dose altered the levels of total cholesterol, HDL cholesterol, or apolipoproteins A-I and B-100, substances that may be related to heart disease risk. It is concluded that the beneficial effects of low doses of fish oils appear to result from changes in the fatty acid composition of blood cells, rather than from changes in blood lipid levels. Higher doses of fish oils may, in addition, alter blood lipid levels, as they lowered triglycerides in this study. (Consumer Summary produced by Reliance Medical Information, Inc.)

Background: Only a few published studies in children used several methods to compare body fat in large groups of fatter and leaner multiethnic children. We hypothesized that the preferred methods of determining body fat may differ in children with larger compared with smaller amounts of body fat, in boys compared with girls, and in African Americans compared with whites. Objective: Our objective was to evaluate several methods of predicting body fat in 10-12-y-old white and African American boys and girls. Design: The body fat of 129 African American and white boys and girls aged 10-12 y, distributed equally by sex and race, was measured with use of dual-energy X-ray absorptiometry (DXA), underwater weighing (densitometry), isotope dilution ([H.sub.2][sup.18]O), bioelectrical impedance, skinfold thicknesses, corporal diameters, and circumferences. Results: With use of DXA as the criterion variable, body fat was bimodally distributed in the boys and skewed to higher values in the girls. Biceps skinfold thickness had the highest predictive value of any single skinfold thickness compared with DXA fat. All formulas for estimating body fat from skinfold thicknesses, body density, or impedance performed better in the children in the upper one-half of the fat distribution (the fatter children) than in those in the lower one-half (the leaner children). Body mass index was highly correlated with body fat ([R.sup.2] = 0.77); there was a good correlation for the fatter children ([R.sup.2] = 0.66) and no correlation for the leaner children ([R.sup.2] = 0.09). The hydration of the fat-free mass was significantly higher in the fatter children than in the leaner ones (79.2% compared with 76.7%). Conclusions: These data are consistent with the hypothesis that all methods of estimating body fat work better in children with larger amounts of body fat. The best formulas use skinfold thicknesses, bioelectrical impedance, and a 4-compartment model. Am J Clin Nutr 2001;73:687-702. KEY WORDS DXA, dual-energy X-ray absorptiometry, bioelectrical impedance analysis, skinfold thicknesses, densitometry, isotope dilution, children, body fat, ethnicity, race

Background: Dietary fatty acids that are more prone to oxidation than to storage may be less likely to lead to obesity. Objective: The aim of this study was to determine the effect of chain length, degree of unsaturation, and stereoisomeric effects of unsaturation on the oxidation of individual fatty acids in normal-weight men. Design: Fatty acid oxidation was examined in men consuming a weight-maintenance diet containing 40% of energy as fat. After consuming the diet for 1 wk, subjects were fed fatty acids labeled with [sup.13]C in the methyl or carboxyl position (10 mg/kg body wt). The fatty acids fed in random order were laurate, palmitate, stearate, oleate, elaidate (the trans isomer of oleate), linoleate, and linolenate blended in a hot liquid meal. Breath samples were collected for the next 9 h and the oxidation of each fatty acid was assessed by examining liberated [sup.13][CO.sub.2] in breath. Results: Cumulative oxidation over the 9-h test ranged from a high of 41% of the dose for laurate to a low of 13% of the dose for stearate. Of the 18-carbon fatty acids, linolenate was the most highly oxidized and linoleate appeared to be somewhat conserved. [sup.13]C recovery in breath from the methyl-labeled fatty acids was [approximately equals] 30% less than that from the carboxyl-labeled fatty acids. Conclusions: In summary, lauric acid is highly oxidized, whereas the polyunsaturated and monounsaturated fatty acids are fairly well oxidized. Oxidation of the long-chain, saturated fatty acids decreases with increasing carbon number. Am J Clin Nutr 2000;72:905-11. KEY WORDS Lauric acid, myristic acid, palmitic acid, oleic acid, trans fatty acid, stearic acid, linoleic acid, linolenic acid, oxidation, dietary fatty acids, obesity

The present study compares reported food intake and energy expenditure of nutrition professionals with that of control subjects. Since previous research on the accuracy of self-reported food consumption has routinely revealed underreporting of food intake, we were particularly interested in investigating whether nutrition professionals could keep better food records than non-professionals. Food intake was obtained from 7-day weighed food intake records for which subjects were provided scales, followed a week later by 7-day measured food intake records using no scales. Energy expenditure was measured with doubly-labeled water for 8 days during the weighed food intake. A total of 10 female dietitians and 10 non-dietitian control women were recruited for this study and both groups received an identical training module for keeping the food record. The groups were similar in demographics; body weight for the dietitians was 61.3 [+ or -] 2.5 kg and for the controls was 63.3 [+ or -] 3.5 kg; body mass index for both groups was approximately 23. Energy expenditure of the dietitians and controls was similar (mean [+ or -] SEM: 2154 [+ or -] 105 kcal/d for the dietitians and 2315 [+ or -] 90 kcal/d for the controls). The dietitians underreported their intake by an average of 223 [+ or -] 116 kcal/d, which was not significantly different from their energy expenditure. The control group, as hypothesized, significantly underreported their energy intake (429 [+ or -] 142 kcal/d, p