OBJECTIVE: Current care for overweight children is controversial, and only few data are available concerning the process of care, as well as the outcome under real-life conditions. METHODS: A nationwide survey of treatment programs for overweight children and adolescents in Germany identified 480 treatment centers. From 135 institutions that had agreed to participate in this study of process of care and outcome, 48 randomly chosen institutions were included in the study. All 1916 overweight children (mean age 12.6 years, 57% female, mean body mass index 30.0 kg/m(2)), who presented at these institutions for lifestyle interventions, were included in this study. Diagnostic procedures according to guidelines and effect of lifestyle interventions on weight status at end of treatment were analyzed. RESULTS: Children treated <3 months were older and more obese, whereas children with >3 months treatment duration demonstrated more cardiovascular risk factors at baseline. On the basis of an intention-to-treat analysis, 75% of the children reduced their overweight. The reduction of overweight varied widely between the treatment institutions (intracluster correlation coefficient 0.15 in the multiple regression model reflecting the intracenter correlation). Screening for hypertension, disturbed glucose metabolism and dyslipidemia was performed in 52% of the children at baseline and in 10% at the end of intervention. CONCLUSION: Overweight reduction is achievable with lifestyle intervention in clinical practice. However, because the clientele, treatment approach and outcome varied widely between different institutions, and screening for comorbidities was seldomly performed as recommended, quality criteria for institutions have to be implemented to improve medical care of overweight children under real-life conditions.