[Longitudinal changes in body composition and basal metabolic rate in institutionalized or domiciled obese...

The prevalence of obesity in children has increased dramatically during the past decades, and requires efficient care.

To determine changes in anthropometric parameters and basal metabolic rate (BMR) in obese adolescents during and after 2 types of weight-reduction programs.

Twenty-six adolescents (group I, Z-score of BMI = 4.72) followed a 9-month-weight reduction program including a moderate energy restriction and regular physical activities in a specialized institution. In addition, 39 adolescents (group E, Z-score of BMI = 2.83) followed at home a 9-month-weight reduction program including medical and dietetic advices. Body composition (by impedancemetry) and BMR (by indirect calorimetry) were assessed before the beginning (M0), 4 months after (M4) and at the end (M9) of the programs, then 4 months (M13) and 16 month (M25) after the end of the weight-reduction programs.

Twenty-two adolescents in group I and 20 adolescents in group E completed the study. At M0, age, body weight (BW), fat-free mass (FFM) and BMR of subjects of group I were higher (1.0 year, 36 %, 30 % and 23 %, respectively, P < 0.001), than those of group E. Pubertal stage and percentage of fat mass (FM) were not significantly different between the 2 groups. At M9, adolescents of group I showed significant reductions in BW and FM (-19 and -37 %, respectively, P < 0.001), but not significant differences in FFM. In addition, BMR decreased significantly between M0 and M4, both in absolute value (-6.7%, P < 0.001) and after adjustment for FFM (-5.8%, P < 0.001), and the difference was maintained until M9. Between M9 and M13, BW and Z-score of BMI were maintained in 12 adolescents, but increased (+9.7% and 14.8%, respectively, P < 0.001) in 10 adolescents. However, BMR did not change significantly in all adolescents. Between M13 and M25, BW, FM, FFM and BMR increased significantly (+13%, +34%, +6% et +5%, respectively, P < 0.001). During the 25 month period, adolescents of group E showed significant increases in BW, FFM and BMR (+8%, +14% and +10%, respectively, P < 0.001), and maintained their Z-score and FM.

The reduction in BMR during the weight-reduction program at the institution could contribute to body weight regain in the post-obese adolescents if they do not maintain the lifestyle habits taught during the weight-reduction period. In other respects, Z-score was stabilized in 51% of domiciled obese adolescents.