Study Protocol For A Randomized Controlled Trial Comparing Two Low-Intensity Weight Loss Maintenance Interventions Based On Acceptance And Commitment Therapy Or Self-Regulation

Background: Weight regain is common following behavioral obesity treatment and attenuates many of the benefits of initial weight loss. This paper describes a randomized controlled trial that will evaluate the efficacy of two low-contact weight loss maintenance interventions based on Acceptance and Commitment Therapy (ACT) and self-regulation (SR). Potential mechanisms of action and moderators of treatment effects will also be evaluated.Methods: Adults (anticipated N = 480) with overweight or obesity will complete an initial 3-month online weight loss program (Phase 1). Participants who achieve ?4 kg weight loss (anticipated N = 288) will then be randomized to an ACT or SR weight loss maintenance intervention. Both interventions will entail four 2.5 h, face-toface, group-based workshop sessions and 6 months of email contact. Assessments will be conducted at phase 1 baseline, phase 1 completion/pre-randomization, and 6, 12, 18, 24, and 30 months post-randomization. The primary outcome will be weight change for the period from randomization to 30 months. Potential process measures including ACT-based constructs (e.g., psychological acceptance, values-consistent behavior), selfweighing frequency, and motivation will be also be assessed, as will potential moderators (e.g., initial weight loss).Conclusions: This study will compare the efficacy of two intervention approaches (ACT and SR) delivered in a scalable workshop format for long-term weight loss maintenance. Future research could examine efficacy and cost-effectiveness of these approaches in real world settings.