Attaining and maintaining healthy weight is a major public health goal for preventing diabetes. While intensive lifestyle interventions are successful in weight loss and reducing risk of diabetes, low socioeconomic status (SES) populations, which have a higher burden of obesity, are difficult to reach with health system or population-based weight loss interventions. The workplace offers a potentially effective setting for health promotion programs aimed at low SES populations. The proposed study team brings together nationally recognized research teams with complementary expertise in community-based obesity prevention and in workplace health and safety interventions to test a workplace intervention program targeted at low SES workers. Working in partnership with BJC HealthCare, a large health care employer with many low-wage workers, this project will evaluate modifiable work environment and individual-level barriers and facilitators of healthy eating and activity (Aim 1). Guided by this formative work, the study team will adapt existing group- and individual-level intervention models to promote healthy weight among workers. We will develop and test an innovative multi-level intervention that includes an interactive obesity treatment program (iOTA) using SMS text messaging (Aim 2B). This innovative mHealth intervention is embedded in a newly described Healthy Workplace Participatory Program, which incorporates employee participation in decision making to produce changes in the workplace environment that are acceptable, effective, and sustainable (Aim 2A). These nested interventions will be tested a large delayed-start group-randomized trial. This study will rigorously test readily scalable interventions that can be translated to other work settings to reduce obesity and diabetes risk among low SES workers, a group at high risk for these disorders. This pragmatic clinical trial will advance the long- term goal of enabling employers and employees to reduce obesity and obesity-associated illnesses including diabetes.