Designing with dissemination in mind: Development and evaluation of a theory-based physical activity intervention using the Multiphase Optimization Strategy - PROJECT SUMMARY/ABSTRACT Difficulty adhering to prescribed health behaviors significantly hinders the long-term benefits of lifestyle weight management programs, leading to an increased risk of cardiovascular disease (CVD) and early mortality. Although physical activity (PA) is one of the best predictors of sustained weight loss, long-term adherence to PA remains poor in adults with overweight or obesity enrolled in lifestyle weight management programs. Absence of accessible, effective, theory-based programs that account for each person’s values and preferences remains a major barrier. Thus, novel, person-centered, and scalable interventions are urgently needed to effectively promote PA adherence in adults with overweight or obesity to enhance weight loss maintenance and CVD prevention. The overall objective of this K01 Career Development Award is to expand and pilot test a theory- based PA program (called MOVE+) designed to enhance motivation in adults with overweight or obesity enrolled in a lifestyle weight management program. First, I will engage stakeholders to assess the initial acceptability of the MOVE+ intervention components. User-centered design testing will occur over 2 cycles: 1) initial stakeholder review of MOVE+ component design and content, and 2) a 12-week, single-arm field trial to pilot test delivery of the MOVE+ program. Second, I will evaluate the feasibility of delivering MOVE+ within an existing lifestyle weight management program (Prevent T2). I will recruit 80 adults with BMI 25-45 kg/m2 to receive 6 months (with 12 month follow-up) of remote delivery of the Prevent T2 program, integrated with the MOVE+ program. To isolate which MOVE+ components are “active ingredients”, I will employ the Multiphase Optimization Strategy and conduct a cluster randomized 2^3 full factorial pilot trial. Eight clusters of n=10 participants will be randomly assigned to a combination of 3, MOVE+ components. My long-term goal is to develop an independent research program that focuses on the prevention and treatment of chronic diseases, including obesity and CVD, by designing and disseminating theory-based, optimized PA interventions that promote sustained behavior change. Along with my mentorship team (Drs. Catenacci, Masters, Kwan, Conroy, Pfammatter, Pyle, and Ms. Barnard), I have developed a comprehensive training plan to support this career goal. My primary training goals include to develop expertise in: 1) the application of behavior change theory to PA intervention design, 2) dissemination and implementation science, 3) the use of novel frameworks and efficient trial designs, and 4) human clinical trial design and conduct. My past experience, complemented by my expert mentoring team, a robust training plan, and an exceptional environment (the University of Colorado Anschutz Medical Campus) will ensure my success. Completion of this K01 will generate critical preliminary data needed to support a competitive R01 application and will serve as both a superb training opportunity and as an original and meaningful scientific contribution to propel my career goal of becoming an emerging leader in PA and obesity research.