Exploring process variables through which acceptance-based behavioral interventions may improve weight loss maintenance.

Objective: A previously published randomized trial with individuals reporting high internal disinhibition showed significant differences in post-treatment weight change favoring Acceptance-Based Behavioral Intervention (ABBI) when compared to standard behavioral treatment (SBT). This paper examines process variables that might contribute to the observed differences in weight change.

Methods: Participants were 162 adults with overweight or obesity (mean BMI 37.6) randomly assigned to ABBI or SBT. Both interventions provided the same calorie intake target, exercise goal, and self-monitoring skills training. SBT incorporated current best practice interventions for addressing problematic thoughts and emotions. ABBI utilized acceptance-based techniques based on Acceptance and Commitment Therapy. ABBI and SBT were compared on process measures hypothesized to be related to outcome in ABBI and SBT and their association with weight loss outcomes using linear and non-linear mixed models methods and exploratory correlational analyses.

Results: Both the SBT and the ABBI groups showed significant changes over time on all process variables. The only significant between group difference was for values consistent behavior, with the ABBI group improving more as compared to SBT ( t =2.45, p =.016); however, changes in values consistent behavior did not mediate weight change. Exploratory analyses suggest the possibility that changes in process variables were less associated with weight change in ABBI than in SBT after treatment was discontinued.

Conclusions: Both conditions produced significant changes in process variables, however there was little difference between groups. Thus, the results do not provide an adequate process account for the observed weight change differences between ABBI and SBT, leaving important questions that need to be addressed by future research.