Engaging in Recommended Amounts of Exercise Lowers the Risk of Seven Types of Cancer

According to a large new study, doing the recommended levels of leisure-time exercise lowers the risk of seven types of malignancies, including kidney and liver cancers.

The findings came from a pooled analysis of nine prospective studies that included more than 750,000 adults from the U.S., Europe and Australia who had no history of cancer and who self-reported their amounts of exercise.

Among 15 cancer types studied, adherence to recommended exercise amounts lowered the risk of liver cancer by 18% to 27%; of multiple myeloma by 14% to 19%; of non-Hodgkin lymphoma by 11% to 18% in women; of kidney cancer by 11% to 17%; of endometrial cancer by 10% to 18%; of colon cancer by 8% to 14% in men; and of breast cancer by 6% to 10%.

The exercise standards used in the study are recommended in the Physical Activity Guidelines for Americans released by the U.S. Department of Health and Human Services in 2018. The guidelines state that adults should engage in 2.5 to 5.0 hours per week of moderate-intensity activity or 1.25 to 2.5 hours per week of vigorous activity in order to avoid preventable chronic diseases.

The authors of the study defined moderate-intensity activities, such as brisk walking, as those that burn off three to six times as much energy per minute as sitting quietly, or three to six metabolic equivalents (METs). Vigorous-intensity activities were those that were aerobic and burned more than six METs.

Looking separately at moderate-intensity versus vigorous-intensity exercise, the authors found both to be beneficial in preventing colon, breast and kidney cancers but did not collect sufficient data to evaluate each exercise type independently in the other four kinds of cancer.

The researchers also looked at exercise amounts in excess of what was suggested in the guidelines. They determined that doing more than the suggested amount of activity further lowered the risk of colon, breast and endometrial cancers, but did not bring additional benefit in preventing kidney or liver cancers, myeloma or, in women only, non-Hodgkin lymphoma.

This indicates that there is “substantial variation in the underlying biologic mechanisms that link physical activity to different types of cancer,” the authors wrote. “Additional research is needed to better understand these differences.”

The authors embarked on the study to help determine the exact levels of physical activity needed to lower cancer risk. The U.S. Physical Activity Guidelines Advisory Committee had previously evaluated more than 40 reviews and meta-analyses that included multiple studies of this issue, but without determining conclusive answers.

“Our findings provide robust quantitative evidence that supports the new U.S. Physical Activity Guidelines for cancer prevention as well as recommendations that have been promoted by the American Cancer Society, World Cancer Research Fund International, the International Agency for Research on Cancer and the American College of Sports Medicine,” the study’s authors wrote.

They added that "These findings provide direct quantitative support for the levels of activity recommended for cancer prevention and provide actionable evidence for ongoing and future cancer prevention efforts."

Alpa Patel, senior scientific director of epidemiology research at the American Cancer Society, noted that, while "physical activity guidelines have largely been based on their impact on chronic diseases like cardiovascular disease and diabetes,” the study’s findings “provide strong support that these recommended levels are important to cancer prevention, as well."

The analysis was conducted by researchers at the National Cancer Institute, the American Cancer Society, the Harvard T.H. Chan School of Public Health and other institutions. Results were published in the Journal of Clinical Oncology in December 2019.