The study will enroll 110 overweight and obese adolescents ages 11-16 in a lifestyle modification program focusing on dietary modification and exercise. Parents will be randomized into control and motivational interviewing-based intervention groups. The primary hypothesis is that adolescents whose parents are in the intervention group will have improved compliance, weight loss and health outcomes compared with adolescents whose parents do not receive the intervention.

Adolescents will participate in a 6-month intensive lifestyle modification that includes a structured exercise program, nutrition education and dietary modification and behavioral support, followed by a 6-month maintenance phase with monthly booster sessions. Parents will be randomized to participate in 4 dedicated "pre-treatment" parent psychoeducational sessions vs. control (no psychoeducational sessions). The sessions will explore parents' feelings about participation in a weight management program, explore their reasons for wanting to make behavioral changes, and enhance motivation. All parents will participate in monthly parent support groups while their adolescents are participating in the intervention phase of the study. The 6-month adolescent intervention will include biweekly sessions with a registered dietitian for dietary education; biweekly interactive group discussion sessions on topics pertaining to motivation, strategies for changing health behaviors, setting and keeping goals and dealing with peer pressure; and exercise sessions three times a week with 30 minutes of cardiovascular exercise and 30 minutes of strength training each session. Comprehensive assessments, including nutrition, behavior and exercise assessments, laboratory work, body composition measurements and medical assessments will be conducted at baseline, 6 months and 12 months.

Inclusion Criteria: Age 11 - 16; BMI > 85th percentile; one parent or guardian committed to participate in protocol; -

Exclusion Criteria: Previous enrollment in IRB3354, IRB3008 or HM11113; Underlying genetic, neurological, endocrine or metabolic condition that preclude weight loss with conventional diet and exercise programs; Weight greater than 400 pounds, Pregnancy in female subjects; Inability to understand study instructions due to language barrier or mental disability; Primary residence outside a 30 mile radius of study location.

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