PROJECT SUMMARY/ABSTRACT Pediatric overweight and obesity continue to be major public health issues. Loss of control (LOC) eating and overeating are two obesity-related phenotypes affecting ~30% of adolescents with overweight/obesity that may undermine weight control treatment outcome. There are very few empirically-supported interventions targeting these behaviors to promote weight regulation in adolescents. Cognitive-behavioral therapy (CBT) has promising effects on dysregulated eating, but effects on weight are often modest. Importantly, CBT fails to adequately address developmental changes in self-regulation, which may limit CBT skill utilization in the moments and contexts in which they are needed most. Moreover, CBT is costly, time intensive, and inaccessible to most teens. Digital interventions overcome many of these barriers and hence may be an optimal format for achieving engagement and scale, especially given the ubiquity of technology usage in adolescents. Our group has tested the only digital CBT interventions targeting dysregulated eating and weight in adolescents with overweight/obesity, and while effects on weight and LOC eating were promising, improved design and updated delivery modes (i.e., Smartphone) are needed to strengthen engagement and clinical outcomes. To achieve optimal engagement and efficacy, such interventions should be built around developmentally appropriate theoretical models and informed by user needs and preferences. In the current proposal, we will apply user-centered design methods to design and test a novel CBT-based digital intervention, augmented with content and features to improve self-regulation, for weight gain prevention and dysregulated eating in adolescents. The intervention will address behavioral, physiological, affective, and environmental processes that impact eating and weight control, informed by self-regulation theories, and will be guided by formative design work to ensure that content and features meet the needs of adolescents for whom it is intended. The first phase will involve design activities with adolescents who have or are at risk for overweight/obesity and report dysregulated eating, to understand desired packaging/presentation, features, and barriers/facilitators to engagement. Research activities will include a needs assessment and iterative prototyping, usability testing, and refinement of the digital intervention. The second phase will be a multisite single arm open trial involving 50 adolescents who have or are at risk for overweight/obesity and report LOC and/or overeating to investigate intervention feasibility and preliminary efficacy, as well as putative treatment mechanisms and targets. Results of the study will directly inform design of a larger, adequately-powered randomized controlled trial and will help advance scientific and clinical understanding of optimal treatment strategies for adolescents with eating- and weight-related problems. Further, the project has clear po...