A workplace multilevel intervention to reduce sugary beverage intake: Can the Compulsive Eating Phenotype guide better treatment matching, and does it work through predicted mechanisms of action? SUPPLEMENT ABSTRACT Sugar-sweetened beverages (SSBs) have emerged as a key dietary risk factor for obesity and type 2 diabetes. We have a new NIDDK-funded trial of the Metabolic Health Improvement Program (MHIP), a randomized controlled trial of a multilevel workplace intervention on a diverse sample, that combines an employer-sponsored sales ban on sugar sweetened beverages (SSBs) with brief counseling (recruitment beginning February 2023). This one-year supplement provides a time sensitive opportunity to build the scientific infrastructure to implement and conduct a thorough “science of behavior change” analysis of why an already successful multilevel intervention works, targeting three candidate mechanisms of change (cravings, stress, efficacy). We are focusing on the high-risk subgroup of those with compulsive eating, with implications for treatment matching, and exploring ethnic/racial and occupational group differences as well. We extend aims of the parent study to discover the MHIP multilevel intervention’s mechanisms of action. Based on our pilot data and focus groups, we propose that being high on the compulsive eating phenotype (CE) increases vulnerability to daily triggers of SSB intake – craving, psychological stress, low self-efficacy and that the brief counseling works in part through these mechanisms. This supplement will allow us to build the infrastructure to assess the CE phenotype, measure the process of change by adding frequent SMS text-based assessments of our proposed daily behavioral mediators (SSB craving, psychological stress, and self-efficacy) and outcome (SSB intake) at 6 timepoints (baseline, immediately post intervention, one month later after last booster session, and then during maintenance (3, 6, and 12 months later). We will characterize a high CE phenotype by assessing links with metabolic disease and high sugar intake (Aim 1), determine whether individuals with high CE synergistically benefit from a workplace multi-level intervention with sales ban and counseling (Aim 2), and ascertain whether any increased benefits are due to reduced daily behavioral mediators of SSB intake (craving, psychological stress, and self-efficacy) (Aim 3). Clarifying the mechanisms of action has importance for the broader science of behavior change and the creation of more effective interventions for obesity and metabolic disease.