For many years it has been accepted that heavy body weight increases a woman's risk for breast cancer. Since weight is one of the few potentially modifiable risk factors for breast cancer identified to date, understanding the relationship between weight and breast cancer is of considerable importance. However, as Huang et al1 state in the first sentence of their article in this issue of JAMA, "The relation of body weight to breast cancer is complex."
See also p 1407.
One of the first complexities to be recognized was that the association between heavy weight and breast cancer applies to postmenopausal women but not to premenopausal women.2 This finding makes sense if, as is commonly believed, estrogens and possibly progesterone are important in the etiology of breast cancer.3 Among premenopausal women, most studies have noted that heavy women have a somewhat reduced risk for breast cancer.4 Recent
Kelsey JL, Baron J. Weight and Risk for Breast Cancer. JAMA. 1997;278(17):1448-1449. doi:10.1001/jama.1997.03550170078037