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Reviewed by the Faculty of Harvard Medical School

Don't Take Breast Cancer Lying Down:
How Exercise Resists The Disease

By Paulette Chandler, M.D., M.P.H.
Brigham and Women's Hospital

How Exercise Blocks The Disease

Exercise is a primary means of preventing breast cancer and improving recovery from breast cancer. Exercise has long been regarded as a means of preventing breast cancer by eliminating excess body fat. Yet, exercise is a weapon against breast cancer beyond its role in weight control. Whether you exercise or not is as important as whether you smoke or eat certain foods such as fruits and vegetables.

Why do physically active people have a lower risk of developing breast cancer? Engaging in regular physical activity helps to regulate and rejuvenate several of the body's regulatory systems, just as being overweight disrupts and destroys the body's environment. Exercise influences the production of many hormones and growth factors, such as estrogen, insulin, insulin-like growth factor, which have an impact on breast-cancer risk. In overweight individuals, the excess fat cells continually produce high amounts of these cancer-related hormones and growth stimulators. For example, overweight people have high levels of estrogen and insulin-like growth factor, which stimulate more breast cancer cells to reproduce.

Physical activity helps to eliminate fat deposits in the body, thereby making it harder for toxic waste products such as dietary carcinogens to be stored long term in the body.

Exercise Prescription for Breast-Cancer Prevention

Try to accumulate 30 to 60 minutes of moderate- to vigorous-intensity activity at least five days a week. Moderate to vigorous means any activity that elevates your heart rate 50% to 70% of its maximum, or causes you to sweat. For walking, think of moderate-intensity as walking as if you were late for an appointment.

Exercise for Breast-Cancer Patients

As a breast-cancer patient, you may feel overwhelmed with fatigue and nausea and unable to exercise. People often assume that the best treatment for fatigue is to relax, but too much rest actually worsens fatigue. You may be too exhausted to keep moving for long periods, but enjoy success with exercise by starting slowly and doing what you can. Even a light walking program can boost energy level, soothe nausea, improve self-esteem, reduce feelings of anxiety and depression, relieve stress and improve overall quality of life. Daily exercise is best, especially for deconditioned patients who may only be able to do light-intensity activities for short periods of time.

Help your body fight breast cancer from within by building a stronger immune system and maintaining a healthy weight. Exercise strengthens the immune system by enhancing the body's natural antioxidant defense system and other immune defenses, in addition to increasing natural killer-cell activity. Studies show that immune-system function is better in breast-cancer patients who exercise regularly compared with those who do not exercise. Weight is a strong predictor of breast cancer recurrence and survival: Overweight women are more likely to have a recurrence of breast cancer.

Exercise also can reduce the risk of lymphedema (arm swelling after breast surgery), heart disease and osteoporosis — all potential side effects of breast-cancer treatment. You may need to modify your exercise routine if you have fatigue during treatment, physical impairments from surgery and other treatments, or breast cancer that has spread to the bones.

Exercise is an important weapon for patients in their battle against breast cancer because it has a profoundly positive effect on physical, functional, and emotional well-being. Spend time with people you care about while enjoying some exercise. Fly a kite, feed some ducks, walk along the beach or walk the dog. Don't forget to include exercise in your daily activities. Try taking the stairs instead of the elevator, parking farther away or using bicycle instead of car for certain errands. Choose activities that help you develop new skills and take place in an environment that calms and nourishes your mind and spirit. Be sure to check with your physician about when to begin your exercise program and how much physical activity is right for you. Ask for guidance in developing an individualized exercise program.

Paulette Chandler, M.D., M.P.H., is a clinical instructor of medicine at Harvard Medical School and an attending physician at Brigham and Women's Hospital.

Last updated January 26, 2011