In sum, excess body weight and inactivity have emerged as strong avoidable causes of postmenopausal breast cancer, with the greatest potential for primary prevention occurring during the premenopausal years. However, surprisingly, no study to date has examined the effects of a standard behavioral weight loss intervention on breast cancer risk markers in premenopausal women. Understanding the effects of weight loss in premenopausal women is a critical next step in existing research and will inform the development of future breast cancer primary prevention programs. The purpose of this study is to determine the feasibility of recruiting, treating, and retaining 20 overweight/obese women in a 12-week randomized control trial examining feasibility and effects of a behavioral weight loss program on breast cancer risk markers in premenopausal women. Participants will be randomly assigned to either a 12-week comprehensive behavioral weight loss program (n=10) or control condition (n=10). All women will be assessed at baseline and after 3 months of treatment.