A Community-Based Behavioral Intervention and Body Mass Index in School-Aged Children: A Cluster Randomized Clinical Trial.

Importance: Childhood obesity remains a major concern in the US, with increases in body mass index (BMI) observed during and after the COVID-19 pandemic. Scalable behavioral interventions are needed to support obesity prevention in community settings. Objective: To evaluate the efficacy of a community-based behavioral intervention (H2GO!) on BMI z scores (zBMIs) among school-aged children. Design, Setting, and Participants: This cluster randomized clinical trial was conducted from September 2020 to June 2025 across 11 Boys & Girls Club sites in Massachusetts. Sites were pair-matched and randomized to intervention or usual care condition. Participants included children aged 8 to 13 years and their parents or caregivers. Intervention: Twelve group-based sessions delivered in person over 6 weeks by trained Boys & Girls Club staff using behavioral strategies to reduce sugar-sweetened beverage intake and increase water consumption through health sessions, youth-created narratives, and parent-child activities. Comparison sites received usual programming. Main Outcomes and Measures: Outcomes were assessed at baseline and at 2, 6, and 12 months using intention-to-treat analyses. The primary outcome was 12-month change from baseline in child zBMI, derived from staff-measured height and weight using standardized protocols. Secondary outcomes included child sugar-sweetened beverage and water intake measured using a validated questionnaire. Results: Among 437 child participants (mean [SD] age, 10.1 [1.2] years; 219 girls [50.1%]), 0.2% were American Indian or Alaska Native, 1.8% were Asian, 15.8% were Black or African American, 42.6% were Hispanic or Latino, and 29.5% were White; 297 (68%) were eligible for free or reduced-price lunch. At baseline, 74 children (16.9%) had overweight, and 161 (36.8%) had obesity. From baseline to 12 months, the mean zBMI did not statistically significantly decrease (-0.11 [95% CI, -0.25 to 0.02]) in the intervention group and did not statistically significantly increase (0.08 [95% CI, -0.04 to 0.20]) in the comparison group; however, the estimated between-group difference in the adjusted mean zBMI change from baseline was statistically significant: -0.19 (95% CI, -0.38 to -0.01; P = .04). Between-group differences in sugar-sweetened beverage and water intake were not significant. Conclusions and Relevance: In this cluster randomized clinical trial, a community-based behavioral intervention was associated with a statistically significant between-group difference in zBMI change among school-aged children. Findings support the potential of community-based behavioral interventions in obesity prevention. Trial Registration: ClinicalTrials.gov Identifier: NCT04265794.