Background. Obesity has become the most common pediatric chronic disease in the modern era. Early prevention and treatment of childhood and adolescent obesity is mandated. Surprisingly, however, only a minor fraction of obese children participate in weight reduction interventions, and the longer-term effects of these weight-reduction interventions among children have not been elucidated. Objective. To examine prospectively the short- and long-term effects of a 3-month, combined dietary-behavioral-physical activity intervention on anthropometric measures, body composition, dietary and leisure-time habits, fitness, and lipid profiles among obese children. Methods. In this randomized prospective study, 24 obese subjects completed the 3-month intervention and were compared with 22 obese, age- and gender-matched, control subjects. Results. At 3 months, there were significant differences in changes in body weight ( - 2.8 +/- 2.3 kg vs 1.2 +/- 2.2 kg), BMI ( - 1.7 +/- 1.1 kg/m(2) vs - 0.2 +/- 1.0 kg/m(2)), body fat percentage ( from skinfold tests; - 3.3 +/- 2.6% vs 1.4 +/- 4.7%), serum total cholesterol level ( - 24.6 +/- 15.1 mg/dL vs 0.8 +/- 18.7 mg/dL), low-density lipoprotein cholesterol level ( - 23.3 +/- 15.2 mg/dL vs - 3.7 +/- 17.3 mg/dL), and fitness ( 215 +/- 107 seconds vs 50 +/- 116 seconds) in the intervention group versus the control group. After a 1-year follow-up period, there were significant differences between the intervention group ( n = 20) and the control group ( n = 20) in body weight (0.6 +/- 6.0 kg vs 5.3 +/- 2.7 kg), BMI ( - 1.7 +/- 2.3 kg/m(2) vs 0.6 +/- 0.9 kg/m(2)), and body fat percentage. There was a significant increase in leisure-time physical activity among the intervention participants, compared with a decrease among the control subjects. Conclusions. Our data demonstrate the short- and longer-term beneficial effects of a combined dietary-behavioral-physical activity intervention among obese children. These results highlight the importance of multidisciplinary programs for the treatment of childhood obesity and emphasize their encouraging long-term effects.