Overweight and obese women who maintain a Western diet may develop dense breast tissue that may increase their risk for breast cancer, according to a study published in Obstetrics and Gynecology.

Researchers looked at data from 3,584 women collected between October 2007 and July 2008, including medical information, family and personal health history, and self-reported information about diet. Breast density for each woman was measured with mammography.

They found that women who followed more of a Western diet, including consumption of high-fat dairy products, processed meats, refined grains, sweets and sweetened drinks, fast foods, and sauces, were more likely to have high breast density. Of note is that the association was seen only among women who were overweight or obese.

In contrast, women who followed more of a Mediterranean diet, characterized by consumption of fish, vegetables, legumes, potatoes, fruits, olives, and vegetable oils, did not have high breast density. Those with the highest adherence to a Mediterranean diet had a 44% lower risk of breast cancer than those with the highest adherence to a Western diet.