SEATTLE, July 20 (UPI) -- Women with higher levels of estrogen have an increased risk of breast cancer because estrogen can spur the growth of some tumors, U.S. researchers say.
However, Anne McTiernan of the Fred Hutchinson Cancer Research Center in Seattle said research also indicates an estrogen-lowering benefit from weight control.
McTiernan and colleagues analyzed data on 439 healthy overweight or obese post-menopausal women. Some did moderate exercise; others dieted moderately, exercised and dieted; some did nothing. The researchers looked at their estrogen levels.
"We found the greatest effect in the group that had both diet and exercise, and we think that's because they lost the most weight," McTiernan said in a statement.
The study was published in the Journal of Clinical Oncology.