PROJECT SUMMARY/ABSTRACT Obesity treatment guidelines recommend comprehensive behavioral weight loss treatments as the first line approach for adults with either obesity or overweight with a weight-related comorbidity. However, the vast majority of adults who are eligible for these weight loss treatments do not initiate them, even when offered at no cost. For individuals who decline weight loss treatment, obesity guidelines suggest a focus on weight gain prevention. Unfortunately, existing interventions to prevent weight gain have the same characteristics that cause many individuals to reject weight-loss treatments in the first place, such as didactic-focused meetings and prescriptions for dietary and physical activity change. To prevent weight gain while overcoming these common barriers to engaging in weight management interventions, we propose an intervention that prescribes self-weighing but does not prescribe changes in diet or physical activity behaviors or require attendance at didactic-focused meetings. The potential of self-weighing to promote weight management is supported both by self-regulatory theory and empirical research. Promoting self-weighing may activate participants’ self- regulatory skills, leading to spontaneous decisions to reduce calorie intake or increase physical activity, thus preventing further weight gain. The proposed intervention will also provide individuals with text message-based feedback to promote continued self-weighing and to motivate engagement with evidence-based resources for weight management at a time when they may be more open to using these resources—e.g., after experiencing a small weight gain. The current proposal will investigate the feasibility and acceptability of this low burden self-weighing intervention in order to prepare for a fully-powered, pragmatic randomized controlled trial. We will enroll 60 primary care patients with either obesity or overweight with a weight-related comorbidity and who have declined to participate in a comprehensive behavioral weight management program. Participants will be asked to weigh themselves daily via a “smart” scale that transmits weight data directly to the study team via the cellular network. Every-other week, participants will be sent text messages providing brief feedback encouraging continued self-weighing. Moreover, if a small weight gain is observed, participants will be sent text messages aiming to engage them in commercial or community-based evidence-based weight management resources. In a single-arm design, all enrolled participants will receive the intervention for 12 months and will complete assessments at 3 and 12 months to assess feasibility and acceptability of the intervention and trial design, while weight will be obtained from participants’ Electronic Health Records (EHR). We will evaluate our success in meeting pre-specified metrics for trial feasibility and intervention acceptability outcomes, including intervention enrollment, intervention...