An individual participant data meta-analysis investigating the mediating role of eating behavior traits in Acceptance and Commitment Therapy-based weight management interventions

Background: Identifying mechanisms of action can aid the refinement of weight management interventions. Acceptance and Commitment Therapy (ACT)-based interventions may support long-term weight management by improving self-regulation of eating behavior traits (EBTs). However, it remains unclear if changing EBTs like emotional eating, external eating, internal disinhibition, and restraint during ACT causes improved weight management. Methods: For this 1-stage Individual Participant Data (IPD) meta-analysis, we requested IPD from 9 trials identified through a systematic search of ACT-based interventions for adults with a body mass index >25 kg/m(2) across 8 databases until June 20, 2022. We obtained, checked, and harmonized data from 8 of those trials (N = 1391) and conducted separate structural equation models with complex survey analysis to estimate short- and long-term mediating effects of changes in each EBT on percent weight change. Results: In the short-term (ie, follow-up closest to intervention end), we found indirect effects of the intervention on percent weight change through changes in emotional eating, external eating, internal disinhibition, and restraint. Each 1-unit change in these EBTs led to a 0.02% (95% CI, 0.05-0.001), 0.03% (95% CI, 0.06-0.001), 0.05% (95% CI, 0.11-0.02), and 0.09% (95% CI, 0.14-0.04) decrease in weight, respectively. In the long term (ie, 12 months after intervention end), we found both indirect and total effects for emotional eating, internal disinhibition, and restraint, with EBT changes explaining 23.78%, 23.12%, and 25.64% of total effects. Conclusion: Findings suggest small partial mediating effects of ACT on weight through EBTs. Targeting EBTs may support improved weight management outcomes, particularly in the long term. Lay Summary Helping people manage their weight in the long term is challenging. To improve weight management programmes, we need to understand the mechanisms that lead to weight loss. One possible set of mechanisms are eating behavior traits (EBTs) that influence what and how much people eat. For example, emotional eating and internal disinhibition describe how someone eats in response to negative thoughts and emotions, while restraint reflects how much someone controls what they eat. Some weight management programmes may address EBTs more than others. In particular, programmes using a type of psychological therapy called Acceptance and Commitment Therapy (ACT) teach people to recognize and accept difficult thoughts and feelings, such as food cravings, and may help with traits like emotional eating and internal disinhibition. In this study, we analyzed data from 1391 adults with overweight or obesity who took part in 8 ACT-based studies. We found that improvements in emotional eating, internal disinhibition, and restraint were responsible for some of the weight loss produced by the ACT interventions. These changes explained about a quarter of weight loss after 1 year. This suggests that targeting EBTs could help improve future weight management programmes, but more research is needed to confirm these findings.