Sex Differences in Obese Children and Siblings in Family‐based Obesity Treatment

OBJECTIVE: The primary goal was to evaluate sex differences in child weight control programs that targeted increasing physical activity (increase) or the combination of reducing sedentary behavior and increasing physical activity (combined). A second goal was to evaluate the benefits of family-based interventions on nontargeted siblings. RESEARCH METHODS AND PROCEDURES: Sixty-seven families with obese children and 89 siblings were randomized to interventions that targeted increasing physical activity (increase) or the combination of reducing sedentary behavior and increasing physical activity (combined). Targeted participants and nontargeted siblings were followed for 1 year. RESULTS: At 12 months, boys showed significantly better percentages of overweight changes (-15.8%) for the combined treatment than girls (-1.0%), with no significant differences for the increase intervention for boys (-9.3%) or girls (-7.6%). Boys adhered to treatment better than girls (p < 0.01). Adherence and predilection for physical activity were significant predictors of targeted child weight loss at 1 year in multiple regression analysis. Predictors of sibling weight loss included age, number of siblings, targeted child percentage of overweight change, and the interaction of group assignment by same sex of treated sibling. DISCUSSION: Gender may influence response to programs that attempt to decrease sedentary behavior, and generalization of treatment effects to siblings may depend on the intervention and characteristics of the siblings.