By Dr. Mallika Marshall

BOSTON (CBS) – Carrying around excess weight puts women at higher risk for breast cancer, but a new study shows if women lose weight and keep it off, they can reduce that risk. And it doesn’t take much to make a difference.

Researchers from the American Cancer Society and the Harvard T.H. Chan School of Public Health looked at data on almost 200,000 women ages 50 and older.

They found that women who lost 20 pounds and kept it off had a 32-percent lower risk of developing breast cancer. But losing only 4-to-5 pounds was associated with an 18-percent lower risk. And even if women lost weight and gained some of it back, but not all, they still had a lower risk of breast cancer.

Two thirds of American women are overweight or obese but perhaps some women will be motivated to lose weight knowing it might reduce their risk of breast cancer.

Dr. Mallika Marshall