Cancer: Physical activity linked to lower risk

The study, published Thursday in the Journal of Clinical Oncology, analyzed data from more than 750,000 adults in the United States, Europe and Australia, and found that recommended amounts of physical activity correlated with lower risks of seven types of cancer, of the 15 types that researchers looked at.

With some cancers, most of that reduced risk was seen with the recommended amounts of physical activity. With other cancers, the study found that physical activity well above current recommendations may correlate with the lowest risk levels.

The authors say this “may reflect important differences in the underlying biologic mechanisms for distinct cancer types.”

The authors note their data come from self-reported physical activity at just one point in time and that the majority of people included were white, which could limit how applicable their findings are more broadly.

When adjusting for body mass index, or BMI, the link between endometrial cancer and physical activity disappeared. However, this had a “limited effect” on other types of cancer, the authors said. In addition, a significant association for non-Hodgkin lymphoma was seen only in women, and the same was true for colon cancer in men.

The researchers caution that the study doesn’t definitively show that exercise directly causes cancer risk to drop. Health experts say there may be various other factors at play.

“These other differences, rather than the differences in physical activity, could explain their different cancer risk,” according to the institute. “For example, if someone does not feel well, they may not exercise much, and sometimes people do not feel well because they have undiagnosed cancer.”

A number of other factors have been linked to cancer risk, including smoking, diet and obesity.