ABSTRACT: To describe the theoretical rationale, intervention design, and clinical trial of a two-year weight control intervention for young adults deployed via social and mobile media.A total of 404 overweight or obese college students from three Southern California universities (M(age) = 22( ± 4) years; M(BMI) = 29( ± 2.8); 70% female) were randomized to participate in the intervention or to receive an informational web-based weight loss program. The intervention is based on behavioral theory and integrates intervention elements across multiple touch points, including Facebook, text messaging, smartphone applications, blogs, and e-mail. Participants are encouraged to seek social support among their friends, self-monitor their weight weekly, post their health behaviors on Facebook, and e-mail their weight loss questions/concerns to a health coach. The intervention is adaptive because new theory-driven and iteratively tailored intervention elements are developed and released over the course of the two-year intervention in response to patterns of use and user feedback. Measures of body mass index, waist circumference, diet, physical activity, sedentary behavior, weight management practices, smoking, alcohol, sleep, body image, self-esteem, and depression occur at 6, 12, 18, and 24 months. Currently, all participants have been recruited, and all are in the final year of the trial.Theory-driven, evidence-based strategies for physical activity, sedentary behavior, and dietary intake can be embedded in an intervention using social and mobile technologies to promote healthy weight-related behaviors in young adults.