Changes in lean body mass in obese children during a weight reduction program: effect on short term and long term outcome.

Objective: To study the changes in body composition during a weight reduction program in obese children and adolescents.
Design: A short-term longitudinal study.
Subjects: Forty-one obese children and adolescents (19 M, 22F, age 8.5-14.8 [median 11.8] years.
Measurements: Lean body mass (LBM) was estimated from Resistance Index (RI) obtained by Bioelectrical Impedance Analysis (BIA) before and after the 3 week program.
Results: Mean percentage weight for height at baseline was 151 (s.d. 20)% and significantly decreased at the end of the three weeks (139 (s.d. 18)%, P = 0.005). The mean percentage body fat also decreased (from 46.0 s.d. 5.8% to 41.5 s.d. 6.5%, P = 0.0015). All individuals lost body fat during the three weeks, whereas the change in LBM was heterogeneous. The individual change in body fat was inversely correlated with the change in LBM (r = -0.64, P = 0.0001). After 4 months, 18 out of the 41 children could be reevaluated for height and weight. The regain in body weight during these 4 months was inversely correlated with the change in LBM during the weight reduction program (r = -0.55, P = 0.018).
Conclusions: Changes in LBM during a weight reduction program can predict the short term result those children who manage to increase LBM having the greatest reduction in body fat. Changes in LBM during weight reduction seem also to predict the longterm outcome, a reduction in LBM being associated with greater regain of weight. Weight reduction programs for obese children should focus not only on weight loss but also on maintenance or increase of lean body mass to improve longterm results.