LOS ANGELES, CA (Catholic Online) - Lauren McCullough, a doctoral candidate in epidemiology at the University of North Carolina along with her colleagues set out to find the answer in a new study published in the journal Cancer.

Researchers found that women who exercised about two hours a day five days a week were about 30 percent less likely to develop breast cancer than less active women. More importantly, the intensity of the exercise didn't matter. Moderate, everyday physical activities, like gardening, walking or doing household chores were sufficient exercise for the women to benefit.

The study examined 1,504 women with breast cancer and 1,555 similar women without the disease, aged 20 to 98 years old, who were enrolled in the Long Island Breast Cancer Study Project. The women answered questions about their physical activity over their lifetimes, which included any recreational exercise they did for at least an hour per week for three months or more. Calculating a lifetime composite score for physical activity, researchers used the data to compare across the participants.

Women who did any exercise had a six percent lower risk of breast cancer than those who did not. Certain subgroups of women enjoyed even larger benefits.

The benefits of physical activity were strongest among women who had children and exercised about 10 to 19 hours each week, either during their reproductive years or after menopause. Exercise for these women was associated with a 30 percent lower risk of breast cancer during the study period, compared with women who exercised less, or not at all.

"I was excited by the results because as women tend to age, they get set in their habits, and think that if they haven't been active their whole life, why start now," McCullough says. "But it's important to show that there is research-based evidence that says that you can start exercising after menopause and still enjoy really good benefits."

Among overweight or obese women, with body mass indexes over 30, those who exercised had a lower risk of breast cancer than those who were not physically active. McCullough says that their risk was similar to that of women of normal weight who did not exercise.

"We are excited by that, because it tells women that even if they are overweight or obese, they can still engage in physical activity and while they won't lower their risk of breast cancer [below average], they will not be increasing their risk of the disease," McCullough says.

However -- women who gained weight as they exercised were likely to negate the reduction in cancer risk linked with physical activity. That's because most of the weight women gain after menopause is in the form of visceral fat around the abdomen, which is more metabolically active, promoting unhealthy insulin and sugar levels, leading to accelerated fat deposition and increasing breast cancer risk.

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