Obesity has adverse effects on breast cancer survival and recurrence, and this may be mediated via the insulin resistance that is associated with obesity. This is a matter of exceptional concern for African-American (AA) breast cancer survivors since a greater proportion of AAs than European Americans (EA) are obese, insulin-resistant and diabetic. This proposal seeks to test the effects of weight loss intervention in obese and overweight AA breast cancer survivors (body mass index 25-40 kg/m2, stage I, II, or IIIA cancer, free of recurrence). Subjects (n=100) will be randomized across 3 arms: 1) control; 2) individualized, dietitian-led counseling; and 3) dietitian-led counseling combined with peer counseling using telephone counseling by trained peers who are AA breast cancer survivors successful at weight control. Psychosocial factors that can affect the extent of weight loss achieved will be assessed, including individual, home and community-level factors. Some of these factors may change when weight loss is achieved and will be assessed both before and after intervention. Genetic polymorphisms that have been shown to be associated with increased body weight, insulin resistance, lipid metabolism, and oxidative stress will be determined and related to both baseline and post-intervention anthropometric and biologic measures. This should further help elucidate inter-individual differences in response to weight loss intervention. The possible beneficial effects of weight loss on the health risks associated with obesity will be evaluated with measures of insulin resistance, insulin-like growth factor and lipid levels in blood samples, as well as with blood pressure and anthropometric measures. The effects of weight loss on these measures have been studied in other obese and overweight populations, but there is little data in breast cancer survivors. Finally, we will attempt to determine if beneficial effects of weight loss can be detected in the breast, since this should be related to subsequent breast cancer risk. The breast contralateral to surgery will be subjected to ductal lavage at baseline, 12 and 24 months. The investigators will examine the effects of weight change on markers of oxidative stress in the breast nipple aspirate fluid that is obtained as part of the lavage procedure. Levels of lipid peroxidation are very high in this fluid and have been related to both nuclear atypia and breast cancer risk. The nuclear morphology of epithelial cells obtained by ductal lavage therefore will be quantified as well. Weight loss in obese and overweight AA breast cancer survivors should improve both psychosocial function and biological indicators of health risks.