Best Exercises for Cancer Prevention

Search for the best exercise to prevent cancer and you find lists. The evidence does not support a list. It supports a weekly total. It supports a mix of types. And it supports less sitting.

NCI defines physical activity in broad terms. It is any movement that uses muscle and takes more energy than resting. That covers walking, running, dancing, biking and swimming. It also covers housework, sport and formal exercise. All of it counts toward the same total.

Intensity is measured in METs, short for metabolic equivalent of task. One MET is the energy you burn sitting still.

• Light activity: under 3 METs.
• Moderate activity: 3 to 6 METs.
• Vigorous activity: 6 METs or more.

Sedentary behavior has its own definition. It is any waking activity of 1.5 METs or less while sitting, reclining or lying down. Office work, driving and watching television all qualify.

NCI adds a point that catches people out. A person can be active and still sit for most of the day. The two are separate measures. They are not opposites.

The Physical Activity Guidelines for Americans, second edition, came out in 2018. It is published by the US Department of Health and Human Services. It sets a target for real health benefit and lower risk of chronic disease, cancer included. For adults it recommends:

• 150 to 300 minutes of moderate-intensity aerobic activity each week, or
• 75 to 150 minutes of vigorous aerobic activity each week, or
• an equivalent combination of the two.

Plus two things that often get dropped:

• Muscle-strengthening activity on at least 2 days a week, working all the major muscle groups.
• Balance training for older adults, in addition to the aerobic and strengthening work.

One detail removes the most common excuse. The guideline states this activity can be done in episodes of any length. There is no minimum block. Three ten-minute walks count the same as one thirty-minute walk.

NCI describes strong evidence that higher physical activity is linked to lower risk of several specific cancers. The figures below compare the most active people with the least active.

• Colon cancer: 19 percent lower risk. That comes from a 2016 pooled review of 126 studies.
• Endometrial cancer: 20 percent lower risk. That comes from a pooled review of 33 studies.
• Esophageal adenocarcinoma: 21 percent lower risk. That comes from a 2014 review of 24 studies.
• Breast cancer: 12 to 21 percent lower risk. That comes from a 2016 review of 38 studies.
• Stomach cancer: 19 percent lower risk. That comes from a 2016 review of 22 studies.
• Bladder cancer: 15 percent lower risk in a 2014 review. A pooled study of over 1 million people put it at 13 percent.
• Kidney cancer: 12 percent lower risk in a 2013 review. That same pooled study of over 1 million people put it at 23 percent.

For breast cancer, the drop shows up both before and after menopause. NCI adds one more finding. Women who become more active after menopause may have lower risk than women who do not.

Two honest caveats belong here.

The endometrial effect may be indirect. NCI notes some evidence that activity has to cut obesity for the benefit to show. Obesity is a strong risk factor for that cancer.

Lung cancer is the clearest case of a mixed signal. Activity looks protective, but smoking may explain it. One 2016 review pooled 25 studies. Activity was linked to lower lung cancer risk among former and current smokers. Among people who never smoked, there was no link at all.

For several other cancers the evidence is thinner. NCI lists some blood cancers. It also lists cancers of the pancreas, prostate, ovaries, thyroid, liver and rectum.

One limit applies to the whole field. This evidence comes mainly from observational studies. People report their activity, then are followed for years. That design cannot prove cause. NCI still takes it seriously, for two reasons. Different populations give similar results. And a plausible mechanism exists.

NCI lists the proposed biological mechanisms. Each is tied to specific cancers:

• Lowering sex hormones such as estrogen. It also lowers growth factors linked to cancer. Both matter for breast and colon cancer.
• Keeping blood insulin from running high. That also matters for breast and colon cancer.
• Reducing inflammation.
• Improving immune function.
• Changing how the body handles bile acids. That lowers the gut's exposure to them.
• Moving food through the gut faster. That shortens contact with possible carcinogens.
• Helping prevent obesity. Obesity is itself a risk factor for many cancers.

That last one is worth holding onto. Some of the benefit of exercise runs through weight, and some does not.

Fewer studies have looked at sitting than at exercise. What exists is not reassuring. NCI describes long stretches of sitting, reclining or lying down while awake as a risk factor. It raises the risk of many chronic conditions and of early death. It may also be linked to higher risk of certain cancers.

The fix is not more gym time. It is breaking up the day. Take calls standing. Walk at lunch. Move during television.

In 2018 the American College of Sports Medicine held a roundtable on activity and cancer. NCI summarizes what it found. Exercise training and testing are generally safe for cancer survivors. Every survivor should keep some level of activity.

The evidence is graded, which makes it more useful:

• Strong evidence for mood, energy and function. Moderate aerobic work, resistance work, or both, during and after treatment cut anxiety, low mood and fatigue. They also improve quality of life and physical function.
• Strong evidence on safety with lymphedema. Exercise training is safe in people who have, or might develop, breast-cancer-related lymphedema.
• Some evidence of benefit for bone health and sleep quality.
• Not enough evidence on several other outcomes. That covers heart damage from treatment and nerve damage from chemotherapy. It also covers thinking, falls, nausea, pain, sexual function and tolerating treatment.

The survival findings are striking, though still observational. Take a 2019 review of breast cancer survivors. The most active had a 42 percent lower risk of death from any cause. Their risk of death from breast cancer was 40 percent lower. After colorectal cancer, activity is linked to a 30 percent lower risk of death from that cancer. Death from any cause was 38 percent lower. After prostate cancer, activity is linked to a 33 percent lower risk of death from that cancer, and a 45 percent lower risk of death from any cause.

A workable week looks like this. Five brisk walks of 30 minutes. Two sessions of resistance work, using bands, weights or your own body weight. Some balance practice. That reaches the guideline without a gym.

Exercise is one lever among several. Our page on cancer prevention covers the others. Our page on what raises cancer risk puts the size of each in proportion. If you are in follow-up after treatment, survivorship covers building activity back safely.

• NCI: physical activity and cancer
• Physical Activity Guidelines for Americans, 2nd edition