The goal of the proposed project is to test the effectiveness of a primary care-situated intervention focused on motivating and guiding patients to use empirically supported, freely available online tools for weight loss, including a commercial platform for goal setting and self-monitoring of diet, physical activity and weight (MyFitnessPal) and online communities providing support for weight loss. Over 40% of US adults live with obesity and approximately 35% with overweight, increasing their risk for poorer health, lower quality of life, and higher mortality. The primary care setting has significant potential to help connect patients with effective weight loss programs and tools, given evidence that primary care providers (PCPs) can motivate health behaviors. Despite the potential, due to numerous implementation barriers, PCPs rarely connect patients to empirically supported weight loss approaches. To address these challenges, UTOOLS (Understanding and Treating Overweight and Obesity for Weight Loss Success) was developed with primary care implementation as a central focus. The novel approach takes advantage of freely available existing online tools to support weight loss. To support effective and sustained engagement of patients with these online tools, UTOOLS delivers an interactive “Kickoff” (short videos and personalized feedback) prior to a scheduled PCP appointment, followed by 52 weeks of text messages and emails targeting psychosocial constructs that are hypothesized to influence online tool engagement. UTOOLS takes advantage of the influence of PCPs through PCPs’ “virtual endorsement” of UTOOLS, yet does not rely on PCPs to initiate a discussion about weight and maximizes flexibility of the PCP during clinic time. Pilot studies support the potential of UTOOLS for effectiveness, the feasibility of the proposed trial design, and the potential for implementation in a clinical setting. To test the 52-week UTOOLS intervention, a randomized trial will be conducted in primary care clinics. Fifteen to 20 PCPs will be recruited and enrolled, followed by 453 of their patients across clinics with strong representation from groups under-represented in weight loss interventions, including African American/Blacks, Latinos, men, and individuals with lower income. Patients will be randomized to complete either the 52-week UTOOLS intervention or a 52 week educational control. The primary outcome is the proportion of patients achieving >3% weight loss at 52 weeks. At the same time as effectiveness is evaluated, essential data to inform future real-world implementation will be gathered. The evaluation plan includes a focus on testing a model of engagement with the online tools to inform future digital health interventions. If effective and favorably received by stakeholders in the proposed trial, UTOOLS has substantial potential to be implemented broadly, aided by its use of existing online tools, limited PCP and clinic burden, and ability to be largely d...