Breast cancer risk, and risk of associated co-morbidities such as cardiovascular disease, is highest among overweight or obese women with a previous history of breast cancer. The objective of this study is to test the effectiveness of a tailored nutrition, physical activity, and behavioral weight management intervention for breast cancer survivors against a widely available commercial weight management program. We hypothesize that an intervention tailored to the unique psychological, nutritional, and physical needs of breast cancer survivors will provide superior physiological and psychological benefits compared to an existing commercial program for the general population. To test our hypothesis, we initially conducted a focus group with both breast cancer survivors and oncology affiliated health care providers in order to illicit feedback to develop an intervention customized specifically to breast cancer survivors. Subsequently, in a randomized, multicenter trial, we are studying the effect of the tailored program on overweight/obese women (N=120) with a history of breast cancer (3 months to 5 years post-primary treatment) on body weight and composition, markers of systemic inflammation related to cancer and associated chronic diseases, physical activity habits, dietary intake, health-related quality of life, and program adherence and satisfaction. Assessments will be taken prior to study initiation immediately following the intervention and at 6 months post-intervention to assess long-term maintenance of weight, lifestyle behaviors, and impact on physiological markers of disease risk. This project is unique in that it addresses weight issues in a high risk, understudied population using a tailored approach.