A study published in Medscape Oncology, the Journal of the National Cancer Institute, found that compared with women with stable weight (±2 kg), women with sustained weight loss had a lower risk of breast cancer. This risk reduction was linear and specific to women not using postmenopausal hormones. Women who lost at least 9 kg and gained back some (but not all) of it were also at a lower risk of breast cancer. Other patterns of weight loss and gain over the two intervals had a similar risk of breast cancer to women with stable weight.
Conclusions: These results suggest that sustained weight loss, even modest amounts, is associated with lower breast cancer risk for women aged 50 years and older.
Background: In 2016, the World Health Organization estimated that 40% of women worldwide were overweight or obese.[1] In the United States, more than two of every three adult women were overweight or obese as of 2014.[2] Although high body mass index (BMI) is an established risk factor for postmenopausal breast cancer,[3,4] currently there is insufficient evidence to determine if the increased risk from excess body weight is reversible.[4] Given that breast cancer is the most commonly diagnosed cancer in women worldwide,[5] the question of whether weight loss can reduce breast cancer risk is of great public health importance.