Cancer and Exercise

A study in the Journal of the American Medical Association (JAMA) showed that “among older, long-term survivors of colorectal, breast, and prostate cancer, a diet and exercise intervention reduced the rate of self-reported functional decline compared with no intervention” (Morey 2009).

Exercise combats the fatigue that often accompanies breast cancer and its treatment fighting recurrence:

  • “Women who exercised at least 90 minutes per week on 3 or more days reported significantly less fatigue and emotional distress as well as higher functional ability and QOL [quality of life, ed.] than women who were less active during treatment” (Mock 2001)

What about preventing recurrences of cancers of various sorts? The best data on this topic is retrospective in nature (not based on randomized trials) but is still pretty remarkable.

Breast Cancer and Recurrence

A single paper once “rocked the research community involved in cancer survivorship” (to quote a Duke University professor). The subjects were almost 3,000 breast cancer survivors who were participating in Harvard University’s Nurses Health Study. The paper in question reported a protective association between increased physical activity after a diagnosis of breast cancer and the rates of recurrence, cancer-related mortality, and overall mortality (Holmes 2005).

To understand the significance of this you have to first understand the concept of “MET-hours per week.” MET stands for a “metabolic equivalent task.” One MET equals the energy expended by an individual while seated and at rest. So an activity with a MET value of, say, five means that one is expending five times as much energy than one would typically expend while at rest. Expend that energy for an hour and you’ve got a “MET-hour.” The results of heightened activity were clear-cut (see Table I):

Table I: Effect of Physical Activity on Preventing Recurrences in Breast Cancer Patients

Number of MET-hours of physical activity The relative risk of dying of breast cancer
Less than 3 MET-hours per week 100%
3 to 8.9 MET-hours per week 80%
9 to 14.9 MET-hours per week 50%
15 to 23.9 MET-hours per week 56%
24 or more MET-hours per week 60%

In other words, expending between 9 and 14.9 MET hours per week is optimal. Walking at a strolling pace for one hour equals 3 MET-hours. Therefore, if you put in three hours per week of walking at a moderate pace (about 2 to 3 miles per hour) you can reduce your risk of dying of breast cancer. Even half an hour per day should do the trick. The effect was especially prominent in women with estrogen-receptor positive (ER+) tumors. It’s a small effort with an enormous payoff.

The authors, at Brigham and Women’s Hospital and Harvard Medical School, Boston, concluded in JAMA:

  • Physical activity after a breast cancer diagnosis may reduce the risk of death from this disease. The greatest benefit occurred in women who performed the equivalent of walking 3 to 5 hours per week at an average pace, with little evidence of a correlation between increased benefit and greater energy expenditure. Women with breast cancer who follow U.S. physical activity recommendations may improve their survival.”

In conclusion, This effect is better than most chemotherapy or hormonal therapy drugs. Plus it does not cost anything and its main “side effect” is to make you feel better!


  • Holmes MD, Chen WY, Feskanich D, et al. Physical activity and survival after breast cancer diagnosis. JAMA. 2005 May 25;293(20):2479-86. doi: 10.1001/jama.293.20.2479. PMID: 15914748.
  • Mock V, Pickett M, Ropka ME, et al. Fatigue and quality of life outcomes of exercise during cancer treatment. Cancer Pract. 2001 May-Jun;9(3):119-27. doi: 10.1046/j.1523-5394.2001.009003119.x. PMID: 11879296.
  • Morey MC, Snyder DC, Sloane R, et al. Effects of home-based diet and exercise on functional outcomes among older, overweight long-term cancer survivors: RENEW: a randomized controlled trial. JAMA. 2009 May 13;301(18):1883-91. doi: 10.1001/jama.2009.643. PMID: 19436015; PMCID: PMC2752421. emphasis added.

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