Project Summary Poverty affects over 37 million individuals in the U.S., subjecting them to syndemics – clustered, mutually enhancing epidemics such as obesity, diabetes, and depression that arise from and perpetuate socioeconomic inequality. Syndemic theory underscores a pathway to mitigate syndemics by intervening on a single target within the cluster. Obesity’s high prevalence in poverty; role in increasing leading causes of death (e.g., cardiovascular disease, cancer, dementia); and adverse psychosocial effects (e.g., increased depression) make it a crucial, high priority target. While structural and social factors contribute to obesity in poverty, research shows the effectiveness of individual-level interventions in improving health behaviors and weight when highly responsive to overburdened populations’ needs. At the same time, evidence guiding refinement of interventions is sparse as participants with socioeconomic disadvantage are underrepresented in obesity treatment research. Reflecting this phenomenon, Rx Weight Loss, a fully automated online obesity treatment, has seen limited use among patients with low income despite past work showing it can be delivered effectively through primary care at low cost. Since 72.8% of adults in poverty have a usual primary care provider, and 83% have Internet access, this gap in adoption represents a significant opportunity for public health impact through adaptation of RxWL that increases relevance for traditionally underserved populations. Further, this research is poised to fill a critical gap in obesity treatment literature. Thus, this application aims to revise RxWL content and the process by which primary care providers refer patients to the program (referenced collectively as the “RxWL package”) to maximize responsiveness, reach, and effectiveness for those in poverty. Using mixed methods data collection, this project structures research activities using the Social Marketing Assessment and Response Tool (SMART) and examines implementation outcomes identified by the Consolidated Framework for Implementation Research (CFIR). Primary care provider (n = 23) and patient (n = 16) stakeholders will provide feedback on the existing RxWL package (Aim 1); insights and scientific knowledge will be integrated to produce a low-cost RxWL package prototype (i.e., a PDF with embedded links approximating the intended program) for usability testing (n = 8 providers, 10 patients; Aim 2); and data will drive development of a finalized RxWL package to disseminate through primary care and evaluate in an open trial (n = 12 providers, 32 patients; Aim 3). Aim 3 will examine both implementation and preliminary clinical outcomes, including effects on weight loss and syndemic sequelae; obtain insights for further refinement; and indicate readiness for a larger R- funded clinical trial. Revising RxWL holds high potential to reduce health disparities for those from socioeconomically disadvantaged backgrounds. Moreover, findi...