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National Cancer Institute

Exercise Interventions in Breast Cancer Survivors

Melinda Irwin, M.P.H., Ph.D.
Yale University School of Medicine
New Haven, CT

  • Earlier studies have shown that women who are overweight at the time of breast cancer diagnosis are twice as likely to experience recurrence and death as lighter women. Additionally, women who gained weight (approximately 5 lbs.) after breast cancer diagnosis had a 60-percent increased risk of death compared to women who did not gain weight.
  • Obesity and weight gain can influence cancer risk through their effects on estrogens and insulin, which may increase cell proliferation. High levels of insulin are associated with increased risks of recurrence and death; physical activity has been shown to modulate insulin levels in healthy women. Proposed biological mechanisms for the effects of physical activity on breast cancer prognosis are that physical activity may decrease breast cancer risk or improve prognosis by decreasing estrogen levels and decreasing insulin and insulin-like growth factor (IGF) levels.
  • A study was developed to examine the effects of a year-long exercise program on biological mechanisms associated with breast cancer recurrence and survival. Mammographic breast density, fasting blood levels of insulin, levels of estrogen and insulin-like growth factors, body fat, and quality of life were measured. Initial results showed that women who exercised (average = 132 minutes per week) had modest decreases in body fat and in insulin levels.

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