Body mass index decreased with orlistat but increased with placebo. The relationship between the changes in BMI and body composition is explained through the dual-energy x-ray absorptiometry results obtained from a subset of our study population. The increase in fat-free mass and bone mineral content was similar in both groups, reflecting normal growth. In contrast, change in fat mass was markedly different between groups. In the subset with dual-energy x-ray absorptiometry measurements, the placebo group experienced an increase in body weight (+1.68 kg) with a decrease of 0.6 kg in fat mass while the orlistat group experienced a decrease in body weight (−0.35 kg) and a decrease of 2.53 kg in fat mass. Thus, the difference in absolute weight experienced by participants receiving orlistat was mostly due to a loss in fat mass, suggesting a favorable change in body composition.