Background: Building Healthy Families (BHF) was developed through a community–academic partnership to provide a 12-week family-based obesity treatment program. Nine cohorts of BHF have been delivered in multiple micropolitan settings between 2009 and 2016, but participant outcomes have varied. This study sought to explore the variation in BHF outcomes to identify the necessary and sufficient conditions that are associated with larger 12-week reductions in BMI z-scores.

Methods: A qualitative comparative analysis was used to determine potential causal conditions or combination of conditions associated with larger reductions in BMI z-score. Seventy-five participants with 12-week outcome data were rank ordered as the 10 most successful participants (largest reductions in BMI z-score; m ± std = −0.64 ± 0.18) and the 10 least successful participants (smallest reductions or an increase in BMI z-score; m ± std = 0.02 ± 0.04). The conditions selected for analysis were identified based on theory and the delivery team's experience with implementing BHF.

Results: Necessary conditions (i.e., present in all highly successful participants, but also some less successful participants) included children with high attendance and self-regulation, at least one adult with high attendance and self-regulation, a mother who lost weight during the program and achieved clinically meaningful weight loss. Sufficient conditions (i.e., present in only the highly successful participants) included mothers with self-regulation scores >45% (range 46.7%–98.2%), and children with a combination of high attendance (72%–100%) and self-regulation scores ≥45% (45%–92.7%).

Conclusion: Program implementers should continue to focus on encouraging high attendance and emphasize the necessity of enacting self-regulation strategies at both the child and parent level.