Overweight status is common among women breast cancer survivors and places them at greater risk for metabolic disorders, cardiovascular morbidity, and breast cancer recurrence than nonoverweight survivors. Efforts to promote weight control in this population are needed. The objective of this research was to evaluate the effect of low-fat or low-carbohydrate diet counseling on weight loss, body composition, and changes in metabolic indexes in overweight postmenopausal breast cancer survivors. Survivors (n = 40) were randomized to receive dietitian counseling for a low-fat or a reduced carbohydrate diet for 6 mo. Weight and metabolic measures, including glucose, insulin, HbA1c, HOMA, lipids, hsCRP, as well as blood pressure were measured at baseline, 6, 12 and 24 wk. Dietary intake of fat and carbohydrate was reduced by 24 and 76 g/day, respectively. Weight loss averaged 6.1 (± 4.8 kg) at 24 wk and was not significantly different by diet group; loss of lean mass was also demonstrated. All subjects demonstrated improvements in total/HDL cholesterol ratio, and significant reductions in HbA1c, insulin, and HOMA. Triglycerides levels were significantly reduced only in the low-carbohydrate diet group (-31.1 ± 36.6; P = 0.01). Significant improvements in weight and metabolic indexes can be demonstrated among overweight breast cancer survivors adherent to either a carbohydrate- or fat-restricted diet.