“We do find that excess body fat in those who are post-menopausal with a normal body mass index is associated with about a doubling in the risk of estrogen-dependent breast cancer,” said Dr. Andrew Dannenberg, one of the study’s authors and director of cancer prevention at the Sandra and Edward Meyer Cancer Center at Weill Cornell Medicine.

The American Cancer Society says estrogen-dependent cancers, called ER-positive breast cancer in the study, occur when the receptor proteins in or on cells attach to the hormone estrogen and rely on it to grow.