Effect of Physical Training and Its Cessation on Percent Fat and Bone Density of Children with Obesity

OBJECTIVE: We determined the effect of 4-month periods of physical training (PT) and detraining on percent fat (percent fat) and bone density of children with obesity. RESEARCH METHODS AND PROCEDURES: Subjects were 79 7- to 11-year-old children with obesity; 34 were white, 44 were black, and 1 was Asian, 26 were male and 53 were female. They were randomly assigned to two groups: group 1 engaged in PT for the first 4 months, while group 2 engaged in PT during the second 4 months. Body composition was measured with dual energy absorptiometry, and diet was measured with 4 days of recall for each 4-month period. PT was offered 5 days/week for 40 minutes/session, heart rate monitors were worn, and no dietary information was given; mean attendance was 80%, and mean heart rate per session was 157 bpm. RESULTS: Group by time interactions across the three time-points (from analysis of variance) were significant for percent fat (p = <0.001) and bone density (p = 0.045). Both groups declined in percent fat during the periods of PT, by an average of 1.6% fat units; in the 4 months after cessation of PT, group 1 increased by 1.3% fat. In both groups, bone density increased more during periods of PT (0.025 g/cm2) than during periods of no PT (0.010 g/cm2). No significant PT vs. no-PT differences were found for dietary intake of energy, macronutrients, or calcium. DISCUSSION: This study suggests that regular exercise, without dietary intervention, can enhance the body composition of children with obesity.