Background: Access to evidence-and family-based childhood obesity (FBCO) treatment interventions is a challenge, especially in underserved regions where childhood obesity disparities persist. Objective: Compare two 6-month FBCO treatment interventions, iChoose (high intensity, parent-child dyads) and Family Connections (low intensity, parents only), in one underserved US region. Methods: This unblinded, RCT reports on effectiveness and implementation outcomes. Eligibility included children ages 5-12 with BMI ≥85th percentile. Analyses included descriptive statistics and intention-to-treat Heckman treatment effect models.Results: Enrolled children (n = 139, mean age 10.1 ± 1.7 years, 30% with overweight, 70% with obesity, 45% black, 63% Medicaid) were randomly assigned to iChoose (n = 70) or Family Connections (n = 69). Retention rates were 63% for iChoose and 84% for Family Connection. Among children, 6-month BMI z-score changes were not statistically significant within iChoose [BMI z-score 0.03 (95% CI = À0.13, 0.
19)] orFamily Connections [BMI z-score 0.00 (95% CI = À0.16, 0.16)]. Likewise, parents' BMI changes were not statistically significant. No adverse events were reported.Both programmes were delivered with high fidelity (77%-100%). Engagement in core components was 25%-36% for iChoose and 52%-61% for Family Connections. Implementation costs per child with improved BMI z-score were $2841 for iChoose and $955 for Family Connections.Conclusions: Neither intervention yielded significant improvements in child BMI zscore or parent BMI, yet both were delivered with high fidelity. Relative to iChoose, descriptive data indicated higher retention, better engagement, and lower costs for Family Connections-suggesting that a lower intensity and parent-focused programme may better fit the intended audience's context.