Objectives : The purpose of this study is to investigate the effect of fasting therapy on the changes of body composition in obese adolescents. Methods : We examined the body composition of obese adolescents three times; before fasting, on the second refeeding day, two or four weeks later. Results : Body weight, body mass index(BMI), basal metabolic rate(BMR) and lean body mass (LBM) were decreased during the fasting, whereas percent-fat was increased. After fasting, patients have the dietary period. During this period BMR and LBM were increased and the decrease of percent-fat was continued. Conclusions : It seems that fasting therapy with keeping up well-controlled dietary period and receiving oriental medical management can be useful to decrease percent-fat in obese patients.