Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2003
Publication Date: 8/15/2003
Citation: Treuth, M.S., Butte, N.F., Sorkin, J.D. 2003. Predictors of body fat gain in nonobese girls with a familial predisposition to obesity. American Journal of Clinical Nutrition. 78(6):1212-1218. Interpretive Summary: The aim was to determine the effect of energy expenditure (EE), muscle energetics, and physical fitness on weight and fat gain in non-obese prepubertal girls with and without a predisposition to obesity. Normal-weight girls (n=101) were recruited at 8 years of age according to parental body mass index, with 88 girls completing the 2-year study. Measures of weight, height, and body composition were taken one and two years after baseline measures. Girls underwent baseline measures of energy expenditure by 24-h calorimetry and doubly labeled water, muscle metabolism, and fitness. The girls with 2 obese parents had a higher fat mass (P=0.03) and % fat (P=0.046) than girls with 2 lean parents at Year 1, and a higher fat mass (P=0.047) at Year 2. Adjusted for baseline weight, group, time, ethnicity and Tanner stage, energy expenditure measures (during sleep, at rest, over 24-h) and fitness were negatively associated with fat mass and % fat (P<0.04). Adjusted for baseline weight, group, time, ethnicity and Tanner stage, muscle oxidative capacity was negatively and free-living energy expenditure was positively predictive of changes in % fat between 8-10 years of age in these girls.
Technical Abstract: BACKGROUND: Conflicting evidence exists on the causal factors underlying the development of excess adiposity in children. OBJECTIVE: We determined the effect of energy expenditure (EE), muscle energetics, and physical fitness on weight and fat gain in prepubertal girls with or without a predisposition to obesity. DESIGN: Normal-weight girls (n = 101) were recruited at 8 y of age according to parental body mass index. Eighty-eight girls completed the 2-y study, and the groups were as follows: LN, girls with 2 lean parents; LNOB, girls with 1 obese and 1 lean parent; and OB, girls with 2 obese parents. Measurements of weight, height, and body composition were taken 1 and 2 y after baseline. Girls underwent baseline measurements of EE by 24-h calorimetry and doubly labeled water, of muscle metabolism by (31)P nuclear magnetic resonance, and of fitness. RESULTS: Fat mass (FM) and percentage body fat (%BF) differed significantly between the groups at years 1 and 2; the OB group had higher FM (P = 0.03) and %BF (P = 0.046) at year 1 and higher FM (P = 0.047) at year 2 than did the LN group. After adjustment for baseline weight, group, time, ethnicity, and Tanner stage, sleep EE, basal EE, 24-h EE, and peak oxygen uptake were negatively associated with FM and %BF (P < 0.04). After adjustment for the same variables, muscle oxidative capacity and free-living total EE were negatively and positively predictive, respectively, of changes in %BF between 8 and 10 y of age (both P = 0.04). CONCLUSIONS: Nonobese girls with 2 obese parents have a significant risk of developing obesity. High free-living total EE and low muscle oxidative capacity predict high rates of fat gain.