Obese individuals often return to their obese state after weight loss. Changes in metabolic rate may develop during caloric restriction and may contribute to the inability to maintain weight loss. To assess the effect of drastic and longterm weight loss on resting metabolic rate (RMR) in obese children and adolescents the RMR of 18 obese individuals, aged 10.2 to 13.1 years (mean±SD:11.8±0.8 yrs) were measured by indirect calorimetry (SensorMedics 2900) before weight loss, during a three weeks drastic weight reduction (700 kcal mixed diet) and bimonthly during 8 months follow up. Body composition was assessed by body impedance method (8IA 109, AKERN/RJL).After the three weeks drastic weight reduction RMR significantly decreased for 27% (p<0.01). During the 8 months follow up RMR and kcal/kgLBM Increased concommitantly with the weight gain. Individuals who maintained their weight, however, increased their RMR parallel with increasing LBM. Those, who rapidly gained weight because of increased caloric consumption showed baseline RMR after 2 months.