Exercise may protect against breast cancer

BETHESDA, Md., Oct. 30 (UPI) -- A U.S. government study suggests normal weight women who often exercise vigorously are about 30 percent less likely to develop breast cancer than others.

Researchers said their findings suggest a sedentary lifestyle can be a risk factor for the disease -- even in women who are not overweight.

National Cancer Institute scientists, led by Michael Leitzmann, studied 32,269 postmenopausal women for 11 years. They determined vigorous activities included such tasks as scrubbing floors, chopping wood, digging, fast jogging, competitive tennis, bicycling and even fast dancing.

"Notable strengths of our study include its large sample size, prospective design, high follow-up rate and availability of relevant known or suspected breast cancer risk factors," said Leitzmann. "These features enabled us to minimize any effects from other factors apart from exercise."

The researchers found non-vigorous activity, such as light housework, painting or general gardening, was not protective. Furthermore, vigorous activity was found to only be protective in lean women and not in those overweight or obese.

The scientists said a possible explanation for the stronger apparent effect of vigorous activity among lean over heavy women is that heavier women might misreport non-vigorous activities as vigorous ones.

The study is detailed in the journal Breast Cancer Research.