PROJECT SUMMARY/ABSTRACT This is an application for a K01 award for Dr. Tanya Halliday, an Assistant Professor in the Department of Health & Kinesiology in the College of Health at the University of Utah. Dr. Halliday is establishing herself as an emerging leader in obesity research, specifically in developing efficacious weight loss maintenance interventions. This K01 award will provide Dr. Halliday the support necessary to accomplish the following goals: 1) Strengthen skills in qualitative research and mixed methods approaches; 2) Develop expertise in complex clinical trial design, particularly adaptive interventions and SMART designs with longitudinal follow-up; and 3) Develop advanced research leadership and management skills. To achieve these goals, Dr. Halliday has assembled a mentoring team comprised of a two Co-Primary Mentors. Dr. Molly Conroy, a physician-scientist experienced in performing large-scale health behavior RCTs, including studies of weight loss maintenance, and Dr. Julie Fritz, clinical and translational scientist with expertise in utilizing adaptive interventions, a type of study design which will be developed and tested to prevent weight regain in the proposed K01, and SMART designs. Dr. Halliday will also be mentored in qualitative research methods and analysis by Dr. Susan Zickmund, with Dr. Jincheng Shen serving as an advisor for biostatics for adaptive design trials. The lack of successful long-term weight loss interventions is the greatest challenge for obesity management. Based on recent evidence, and her own preliminary data, Dr. Halliday’s central hypothesis is that an adaptive intervention involving individually tailored re-engagement with professional support will be feasible and able to prevent weight regain following intentional weight loss. She will test this hypothesis by developing and pilot testing and 6-month adaptive re-engagement intervention in adults whom have recently lost a significant (≥7%) amount of weight with lifestyle (diet/exercise) interventions. By pursuing the following specific aims, the applicant will test her hypothesis and gather data for a clinical trial to 1) Qualitatively explore weight regain triggers for weight-reduced adults as well as preferred aspects of an evidence-based adaptive re-engagement intervention; 2) Develop an adaptive intervention to re-engage patients at times they are at risk of weight-regain; and 3) Determine the feasibility of an adaptive re-engagement intervention to prevent weight regain. The proposed research is significant because weight loss interventions are unsuccessful long-term and new approaches to prevent weight regain are needed. The proposed research is innovative because adaptive re- engagement trials have not been evaluated as a weight loss maintenance approach; adaptive interventions are typically not developed with rigorous preliminary work like that proposed in this project; and outcome measures will be evaluated after 6-months of follow-up to d...