A large prospective study reveals that women in their menopausal years or in their 50 s who had a sustained weight loss for 10 years had a reduced risk of breast cancer.
A large study of 180000 women aged 50 or older followed for 18 years found a linear relationship between weight loss and breast cancer risk reduction. Even a weight loss of 10 lbs was related to a 13% lower risk. Additionally, a 20 lb weight loss resulted in 16% lower risk and 26% lower risk for women who lost more than 20 lbs. For the 2/3 rds of American women who are overweight, this is a huge motivation to loose weight. The reason for this observation maybe multifold but may suggest that those losing weight maybe drinking less, exercising and eating better and less. Of course, this information relates to women who are overweight to start with. Overweight women harbor higher levels of Insulin which in itself is an inflammatory agent leading to higher incidence of cancer and other inflammatory conditions.

Reference: The journal of the national cancer institute.