Objective: The authors performed a group-based program for obese children and adolescents in Bavaria, Germany to enable them to establish a health-oriented lifestyle and to reduce overweight. The authors compared this program with a control approach based on the patients' own initiative. Design: This is a controlled clinical trial. Setting: A nutrition program for outpatients in a German university hospital. Participants: Seventy-three obese patients aged 7 to 15 years (mean 11.2 years) were recruited by pediatricians and local newspaper reports and randomized into intervention and control groups. Children and adolescents in each group were divided into 3 groups according to age--7-8 years, 9-10 years, and 11-13 years. Children were classified overweight (defined as body mass index (BMI) greater than 90th percentile for age and gender), obese (BMI greater than 97th percentile), and extremely obese (BMI greater than 99.5th percentile), according to the European Childhood Obesity Group and the German Working Group on Pediatric Obesity, congruent with adult standards used to assess overweight and obesity. Intervention: Thirty-seven patients (age 7-13 years, mean 10.9 years) for the 1-year intervention. This intervention consisted of modules for physical activity, nutritional education, and coping strategies. The program was performed twice each week and incorporated parental participation and medical supervision, including laboratory tests. The obese controls (n = 36, age 8-15 years, mean 11.6 years) received written therapeutic advice during a visit at 0 and 6 months in the outpatient clinic. Main Outcome Measure: The primary outcome variable was the body mass index (BMI) z score. Analysis: Analysis of variance and t test were used, and a P value less than 0.05 was considered significant. Results: There was a reduction of BMI z score in the active treatment group (P less than 0.05), but not for controls. Moreover, the active group showed beneficial effects for body mass index (BMI), fat mass, and systolic blood pressure 12 months after beginning the intervention. Conclusions and Implications: Group-based programs for young, obese patients can be effective tools for establishing a health-oriented lifestyle and reducing the burden of obesity. (Contains 1 table.)