This study investigates to what extent long term effectiveness of weight reduction program in obese adolescents depends on the body composition before therapy and its changes during therapy. Studies were conducted on 78 obese adolescents aged 12-16 years, who participated in a 4-week weight reduction program, which consisted of low energy diet (5.47 MJ per day, 18% protein, 26% fat, 56% carbohydrate) and physical exercises. Body weight (BW) and body composition (fat mass – FM, lean body mass – LBM) were measured using bioimpedance method before and during therapy as well as six months later. After 4-week BW, FM, LBM decreased significantly (p < 0.001). Six months after termination of therapy the mean BW increased, but mainly due to LBM. Mean changes FM (0.29 kg ±3.93) were not significant however in 50% of population FM increased. Correlation between loss of LBM during therapy and FM gain after six months was statistically significant. FM after six months correlated with BW and FM before therapy and changes BW during therapy. Effectiveness of the program could be well predicted by BC before therapy and its changes during therapy. Results permitted to formulate detailed recommendations for weight reduction program for obese adolescents regarding the individual degree of obesity and BC.

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