Change in body composition during a weight loss trial in obese adolescents

What is already known about this subject Adolescence is an important period of physiological growth. Loss of central adiposity with preservation of lean mass during weight loss is optimal. There are discrepancies in the literature concerning changes in lean mass during weight loss in adolescents. What this study adds This study provides information of regional and total body composition change in adolescents during weight loss. This study controls for important factors that impact body composition in growing adolescents such as age, sex, height, baseline weight and race. This study provides correlations of changes in waist circumference and body mass index (BMI) with total and trunk fat mass during weight loss in adolescents.

Background Changes in body composition during weight loss among obese adolescents are poorly understood. This study characterized the composition of weight loss and its association with changes in waist circumference (WC) in obese adolescents. Methods Total (Tot), trunk (Tr) and appendicular (Ap) fat mass (FM) and lean mass (LM) were measured by dual-energy X-ray absorptiometry in 61 obese adolescents (40 girls) who participated in a randomized controlled weight loss trial. Changes in body composition were assessed at 0, 6 and 12 months using mixed-effects regression models. Correlation analysis of change in WC and total and regional compartments of FM and LM were assessed. Results Weight loss for adolescents was 90.3% FM and 15.9% LM at 0-6 months, and 98.2% FM and 7% LM at 0-12 months. At 12 months, girls lost 2.67 kg more TotFM than boys in models adjusted for height, age, race and baseline weight. Boys gained LM in all compartments in all models. At 12 months, girls lost TotLM (2.23 ± 0.74, P < 0.004) and ApLM (0.69 ± 0.31, P = 0.03) and gained TrLM (0.37 ± 0.35, P = 0.29). The percentage LM, increased for boys and girls in all models. TotFM was correlated with body mass index (BMI) change with TotFM (R = 0.70-0.91, P = 0.001) and WC change (R = 0.53-0.55, P < 0.001). Conclusions Weight loss in obese adolescents during a weight loss trial using lifestyle management and sibutramine was primarily from trunk FM. Although absolute LM increased in boys and decreased in girls, the percentage of weight that is LM increased for both boys and girls. Changes in BMI were more reflective of changes in FM than changes in WC.