Background: Treatment studies about childhood obesity in primary care are lacking. We hypothesized that providing a paid family membership to the YMCA would be effective in reducing weight.Methods: Patients 5 to17 years old in at least the 85th body mass index (BMI) percentile were eligible. All participants were scheduled to attend 4 nutrition classes and to return for evaluation at 2, 4, 6, 9, and 12 months. Participants were randomized to nutrition classes only (n ‫؍‬ 39) or nutrition classes and family YMCA membership (n ‫؍‬ 44). The primary outcome measure was year change in BMI-for-age percentile.Results