If you took a walk this morning to improve your heart health or lift your mood, you already know that exercise is good for you. But walking, dancing, stair-climbing, and other kinds of physical activity have an additional health benefit: They can lower your risk of cancer.

In fact, becoming a little more active may be one of the most important things you can do, along with eating a healthy diet and not smoking, to lower cancer risk.

There’s strong evidence that physical activity lowers the risk of bladder, breast, colon, endometrial, kidney, and stomach cancers, as well as one kind of esophageal cancer. It might also lower the risk of lung and other cancers. And people who survive some forms of cancer, including breast and colon cancer, appear to face lower recurrence risks if they are physically active.

Just how does moving your body stop cancers from forming, growing, or returning? While scientists are still seeking some answers, there’s growing evidence that a complex interplay of physical activity, body fat, and other factors play a variety of roles.

One important clue is that many cancers linked to inactivity also are linked to obesity. For example, according to the National Cancer Institute, a woman’s risk of endometrial cancer, which affects the lining of the uterus, is two to four times higher if she is obese or overweight than if she is at a healthy weight. People with obesity have a doubled risk of stomach and kidney cancer and also face heightened risks for colon, pancreatic, and certain esophageal cancers. Obese women who are past menopause have an increased risk of breast cancer.

How it works

Decades of research have detailed how physical activity lowers heart disease risk. Research on physical activity and cancer is at an earlier stage, but it has produced compelling evidence for several theories. Here’s the best current thinking on how physical activity lowers cancer risks:

  • Exercise can reduce levels of sex hormones, such as estrogen and testosterone, that play roles in several cancers, including breast and endometrial cancer. One reason obesity is linked with breast cancer in older women, but not younger women, may be that body fat becomes a major source of estrogen after menopause. Exercise that reduces body fat lowers hormone levels.
  • Exercise can help the body maintain a healthy insulin level. High levels of insulin, a hormone that controls blood sugar, are associated with diabetes. But high insulin levels also can promote the growth of cancerous tumors. High insulin levels and other metabolic problems associated with type 2 diabetes are linked with cancers of the breast, colon, pancreas, and uterine lining.
  • Exercise can reduce inflammation. Inflammation plays an important role in cancer. Physical activity may directly lower inflammation. It also likely reduces inflammation by helping people lose weight and fat. Body fat releases substances that promote inflammation.

Researchers are looking for additional ways physical activity might reduce cancer risks. For example, repeated bouts of exercise might change the immune system in beneficial ways or protect our very DNA from changes that can lead to tumor formation and growth.

What it means for you

You don’t have to run marathons to reap the cancer-preventing benefits of exercise. Research suggests that every bit of added movement helps, whether that means climbing some extra stairs, spending more time working in your home or garden, or getting in more steps by driving less often or parking farther from your destinations.

With that said, research suggests that, for some cancers, protection increases with more movement over a longer period of time. So, if you aren’t yet meeting the U.S. government’s recommendations for physical activity (see sidebar), you might work toward that goal.

Recent studies have found that breast cancer survivors who got about as much physical activity as recommended, the equivalent of a brisk 30-minute walk most days, were significantly less likely to see their cancers return.

Some other takeaways and tips

  • Weight matters, but it’s complicated. While weight loss might help lower the risk of some cancers, it’s better to prevent weight gain in the first place, if you can. For one thing, significant weight loss is hard and virtually impossible to accomplish with exercise alone. Also, some research suggests that people who are already at a healthy weight get a bigger cancer prevention boost from exercise. But studies haven’t sorted out the reasons. If you are already overweight or obese, it’s good to know that physical activity can lower body fat and increase muscle, even if you lose little or no weight. That improvement in body composition alone appears to offer some protection from cancer.
  • How much you sit may matter, too. Cancer studies have not yet shown the impact of how much time you spend sitting, lying down, or otherwise moving very little during your waking day. There’s no doubt that moving more and sitting less is good for your overall health. So, if you find yourself sitting for long periods, be sure to take breaks to get up and move around.
  • It’s never too late to start. While some evidence suggests that people who are physically active throughout their lives may get the biggest cancer prevention boost, there’s also evidence that taking up exercise in later years is beneficial.

How Much Activity You Need

Studies have yet to show exactly how much exercise of what kind provides the strongest protection from cancer. But, keeping in mind that every bit counts, you can’t go wrong following the U.S. government’s physical activity guidelines for adults. That means you should:

  • Aim to move more and sit less throughout the day.
  • Get at least 150 to 300 minutes a week of moderate aerobic activity (such as brisk walking) or 75 to 150 minutes of vigorous aerobic activity (such as running). You could meet the goal by taking five 30-minute walks or a few long jogs, or by mixing in swimming, biking, dancing, tennis, pickleball, or any other activity that gets your heart beating faster.
  • Do muscle-strengthening activities at least two days a week. You might lift some weights, use resistance bands, or do exercises such as squats and push-ups. Even carrying heavy groceries or lawn supplies can count.
  • Work on improving your balance if you are over age 65. Activities such as yoga, tai chi, and ballroom dancing can help.
  • Be as physically active as you can if you have disabilities or chronic health problems that prevent you from following these general recommendations.

Start slowly and gradually build up your activity levels if you have been inactive for a while.

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