INCLUSION CRITERIA:  Participants must:  be between 13 and 17 years of age have BMI greater than or equal to the 95th percentile for age and sex have a parent or guardian available to participate in the study speak English due to the group format of the intervention agree to study participation, measures, and randomization be available for long-term follow-up.  EXCLUSION CRITERIA:  Adolescents will be excluded from study participation if they:  have absolute BMI greater than 50 are currently involved with another weight loss program have a medical condition that would interfere with the prescribed dietary plan or participation in physical activity have a developmental delay such that the intervention materials will not be appropriate report engaging in extreme/unhealthy weight control behaviors including self-induced vomiting, laxative or diuretic use, or report a history of eating disorder, and/or are actively psychotic or suicidal at the time of screening.