Longitudinal studies in infants and children suggest that low total energy expenditure (EE) (TEE) and parental body composition are important predisposing factors to obesity. The aim of this study was to examine potential predictors of changes in total or percentage body fat over 2.7 y in premenarcheal girls. We studied 47 normal-weight prepubertal girls aged 4.8-8.9 y in 3 visits. The girls' age, total and percentage body fat at baseline, sleep EE (SEE) and activity-related EE (AEE) adjusted for fat-free mass (FFM) and total body fat, mothers' and fathers' total and percentage body fat and FFM at baseline, and time to follow-up visits were measured; 24-h EE and SEE were measured by whole-room indirect calorimetry. AEE was calculated as TEE minus (SEE + 0.1 TEE), with the assumption that the thermic effect of food was 10% of TEE. The girls' body composition was measured at each visit and that of the parents was measured at the time of the girls' enrollment by using dual-energy X-ray absorptiometry. From baseline to the first (mean: 1.6 y) and the second (mean: 2.7 y) follow-up visits, the girls' mean (+/-SD) change in total fat adjusted for FFM was 1.2 +/- 2.7 and 3.3 +/- 4.0 kg, respectively, and the mean change in percentage body fat was -2.0 +/- 5.0% and -0. 8 +/- 5.9%, respectively. Fathers' total and percentage body fat were the main predictors of changes in the girls' total and percentage body fat. For the first follow-up visit, SEE, girls' age at baseline, and AEE were significant predictors of percentage body fat. Fathers' total and percentage body fat were predictors of changes in body fat of premenarcheal girls during a 2. 7-y period.