Health Psychology, Vol 45(11), Nov 2026, 1059-1071; doi:10.1037/hea0001612
Objective: Family-based behavioral treatment (FBT) is an evidence-based treatment that has shown statistically significant short- and long-term outcomes for children. However, statistical and clinical significance are different ways to study the impact of a treatment, and recent data have indicated the degree of body mass index z-score (zBMI) change that prevents the development of cardiometabolic disease. Method: We conducted a mega-analysis using an individual participant database extracted from 16 randomized controlled studies (N = 1,098) on FBT for 6–12-year-old children with overweight or obesity and a participating parent with overweight and obesity that had at least 1-year follow-up. These data were used to evaluate clinical effectiveness based on −0.25 zBMI change and what percentage of children showed reversal of obesity at 6-, 12-, 24-, 60-, and 120-month follow-up. Analyses also examined whether age and sex were predictors of zBMI change. Results: Across the combined databases, 70%, 61%, 52%, 54%, and 68% met the −0.25 zBMI criteria, and 29%, 27%, 23%, 46%, and 48% reversed their obesity status at 6, 12, 24, 60, and 120 months, respectively. Age was a reliable predictor of change, with younger children showing greater change up to the 24-month follow-up. Conclusions: These results suggest FBT is associated with clinical effectiveness, with long-term effects stable or improving over time. These data support the utility of FBT, and providing data on the clinical effectiveness of pediatric obesity treatment complements traditional reporting of statistical significance of FBT to support the clinical utility of FBT. (PsycInfo Database Record (c) 2026 APA, all rights reserved)