Over 60% of the American population meets the criteria for obesity, and obesity is very common in patients with breast cancer. Many studies have shown that obese patients with breast cancer have a worse prognosis compared to normal weight individuals. Tumor characteristics and other factors contribute to this. Exercise could reverse some of the pathophysiologic factors that contribute to this increased risk, and has been shown in some studies to improve survival in patients with breast cancer. In addition to administering anticancer therapy, cancer clinicians should make concerted attempts to get patients to enroll in weight management and exercise programs, which could improve survival in patients with breast cancer.