CHICAGO -- Older women can reduce their breast cancer risk by about 20 percent by walking briskly for an hour or two a week, according to a new study.

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The report, published in Wednesday's issue of the Journal of the American Medical Association, found that even women who have used hormone therapy for symptoms of menopause can benefit. The findings are based on the same study that found a slightly higher risk of breast cancer among women on long-term hormone therapy.

"We thought it was important to determine if moderate-intensity physical activities, such as walking, biking outdoors or easy swimming, when initiated later in life, can reduce the risk of breast cancer, since these types of activities are achievable for most women," said lead researcher Dr. Anne McTiernan, of Fred Hutchinson Cancer Research Center.

The activity need not be strenuous, but it should be done consistently, such as taking a brisk, 30-minute walk five days a week, McTiernan said.

The best fat-burning formula involves low- to moderate-intensity exercise that is done over a longer period as opposed to short, intense bursts of activity, she said.

"The bottom line is that duration of activity is more important than intensity. The turtle beats the hare when it comes to preventing breast cancer through exercise," McTiernan said.

She suggested that women should aim for at least 30 minutes of moderate-intensity exercise a day, five days a week.

The study also found a reduced risk in women considered to be at highest risk for breast cancer, such as those with a family history of the disease or hormone replacement therapy use.

McTiernan said the study suggests that exercise may help to counter -- but can't cancel -- the breast cancer risk of hormone treatment.

The team also found that the less a woman weighs, the more regular, moderate exercise appears to have a protective effect.

"There are many benefits for women of any weight to start exercising, like reducing their risk of heart disease and diabetes," McTiernan said. "But in terms of breast-cancer risk, obese women will see most benefit once they start getting their weight down."

Researchers believe that weight plays a role in breast cancer because fatty tissue produces hormones and growth factors, such as estrogen and insulin, which may promote cancer development.

Another study published in the journal found that moderate exercise is just as effective as intense exercise when it comes to women's weight loss. Read the article.

Journal of the American Medical Association