Breast cancer, the most common female malignancy in the world, has a strong association with obesity and insulin resistance. The importance of these risk factors goes up significantly in patients already affected by this cancer as they negatively affect the prognosis, recurrence rate, and survival by various mechanisms. The literature on the role of physical activity and aerobic exercise on modifying the above risks is debatable with data both for and against it. In this article, we have reviewed the risks of obesity and insulin resistance in breast cancer patients and the controversy associated with the impact of exercise. Ultimately, we have concluded that a randomized control trial is necessary with an individualized aerobic exercise program for a minimum duration of 20 wk on breast cancer patients, who are undergoing or recently completed chemotherapy, to study its effects on insulin resistance, weight, and clinical outcome.