Differential effects of a school‐based obesity prevention program: A cluster randomized trial

School‐based healthy living interventions are widely promoted as strategies for preventing obesity. The peer‐led Healthy Buddies™ curriculum has been shown to improve obesity‐related outcomes in school‐aged children. We examined whether these improvements existed among subgroups of children stratified by sex, income level and urban/rural geography. In a cluster‐randomized controlled trial, elementary schools in Manitoba, Canada, were randomly allocated to Healthy Buddies™ (10 schools, 340 students) or standard curriculum (10 schools, 347 students). Healthy Buddies™ participants had 21weekly lessons on healthy eating, physical activity and self‐efficacy, delivered by children age 9–12 to children age 6–8. We assessed pre‐ and post‐intervention body mass index (BMI) z‐scores, waist circumference, healthy living knowledge, dietary intake and self‐efficacy among the younger children. Compared to standard curriculum (n = 154), Healthy Buddies™ participants (n = 157) experienced a greater reduction in waist circumference (−1.7 cm; 95% confidence interval [CI][−2.8, −0.5 cm]) and improved dietary intake (4.6; 95% CI [0.9, 8.3]), healthy living knowledge (5.9; 95% CI [2.3, 9.5]) and self‐efficacy (5.3; 95% CI [1.0, 9.5]) scores. In subgroup analyses, effects for waist circumference (−2.0 cm; 95% CI [−3.6, −0.5]), healthy living knowledge (9.1; 95% CI [4.4, 13.8]) and self‐efficacy (8.3; 95% CI [3.3, 13.3]) were significant among boys. Dietary intake (10.5; 95% CI [5.5, 15.4]), healthy living knowledge (9.8; 95% CI [4.5, 15.0]) and self‐efficacy (6.7; 95% CI [0.7, 12.7]) improved among urban‐dwelling but not rural‐dwelling children. Healthy Buddies™ was effective for boys and children living in urban settings. Enhanced curricula may be needed to improve program effectiveness for select subgroups of school‐aged children.