Being Overweight Increases Breast Cancer Risk in Older Women
It has long been known that being overweight, especially later in life, puts a person at greater risk for certain cancers and diseases. Now a large analysis from the Fred Hutchinson Research Center in Seattle found that older women struggling with severe obesity are 86 percent more likely to contract a common breast cancer, as well as possibly develop other advanced cancers.
For the study, the team collected data for 67,142 post-menopausal U.S. women from the long-standing Women’s Health Initiative Study, then monitored them for 13 years. At the start of the study, all the women were were between 50-79 years old. By 2010, 3,388 of them had been diagnosed with breast cancer.
The scientists grouped the women based on their body mass index (BMI). A BMI of under 25 is classified as ‘normal’, between 25 and 30 is overweight, 30 is considered obese, and over 35 is considered severely obese.
Compared to women of normal weight, women with a BMI of over 35 were found to be 56 percent more likely to be diagnosed with some type of breast cancer, and they were 86 percent more likely to develop breast cancer tumors driven by estrogen and progesterone. These estrogen receptor-positive and progesterone receptor-positive cancers are the most common form of the disease. Researchers found there wasn’t a link between receptor-negative forms of the disease and weight. They also found postmenopausal hormone therapy was ineffective at reducing risk.
This analysis suggests that maintaining a healthy weight is key to preventing breast cancer, since once a person is overweight or obese, “the damage may be done.” Researchers found that normal-weight women who gained 5 percent of their original body weight during the study were 35 percent more likely to develop breast cancer, and that losing weight after already being overweight or obese did not help to lower breast cancer risk.
Researchers are calling for more trials to study in detail, how weight loss later in life may be beneficial.