Effects of a multidisciplinary weight loss intervention on body composition in obese adolescents.

Objective: To investigate if a multidisciplinary weight loss program in adolescents suffering severe obesity allows adequate growth and development and avoid lean mass loss.

Design: A total of 55 adolescents (33 girls and 22 boys) suffering severe obesity were enrolled in an interdisciplinary weight reduction program lasting 6-12 months. Progressive submaximal physical activity was performed and national dietary allowances for adolescents with low levels of physical activity energy were provided.

Measurements: Total and segmental body composition was assessed by means of dual-energy X-ray absorptiometry.

Results: The mean height significantly increased (P<0.001). The mean body mass index (BMI) dropped in boys from 34.5+/-3.2 to 25.5+/-2.3 kg/m(2) and in girls from 38.4+/-4.1 to 28.4+/-4.1 kg/m(2). Height increased according to the expected pattern (P<0.001). Total lean mass (LM) did not vary and was positively correlated to pubertal development in both sexes before and after weight loss. Steepest drop in fat mass (FM) was observed in the trunk (-63.2+/-10.1% in boys and -51.5+/-11.4% in girls). Decrease in BMI and FM was tightly correlated in both sexes. However, slopes significantly differed (P<0.0005) so that a decrease of 1 kg/m(2) in BMI corresponded to a decrease of 3.92 kg in FM in girls and of 5.44 kg in boys. In each sex, FM at baseline and duration of the treatment were the main determinants of the decrease in FM.

Conclusion: During adolescence, despite a major weight loss, adequate growth and preservation of LM can be achieved. Weight loss kinetics markedly differs between boys and girls. Low-calorie diets are unnecessary to achieve a marked reduction of severe obesity during puberty.