According to a study published in JAMA Oncology obese postmenopausal women are exposed to an increased risk of developing breast cancer. Compared to women who had a normal weight, obese women had a 58 percent increased risk of breast cancer. Not only this, but in addition, obese women were more prone to have large tumors.
The research was conducted on more than 67.000 postmenopausal women who had ages between 50 and 79. The participants were enrolled in the WHI (Women’s Health Initiative) clinical trials which consisted of a series of studies concentrated on health issues which postmenopausal women might experience. The participants in the study were enrolled from 1993 to 1998 and the research also had 13 years of follow-up.
The weight and height of the women were measured at baseline. Mammograms, clinical breast exams together with weight measurements were conducted at baseline and annually. During the study the researchers observed 3,388 cases of invasive breast cancer which were verified by physician adjudicators.
The findings of the study suggest a strong, linear dose-response link between BMI (body mass index) and the risk of breast cancer. Obese postmenopausal women presented a 58% increased risk of breast cancer, while women with a normal body mass index who gained more than 5 percent of their body weight presented a risk of cancer development increased with 36%.
In addition women who were obese in the beginning of the study but lost more than 5 percent of their body weight did not experience a reduced risk of breast cancer. According to the lead author of the study, Marian Neuhouser from the Fred Hutchinson Cancer Research Center (Seattle) hormone therapy did not lower risk of breast cancer in obese postmenopausal women. This contradicts many previous studies.
“Obesity is known to increase estrogens in the postmenopausal women because estrogen is made by fat tissue. Fat tissue also secretes inflammatory factors and is associated with insulin resistance – all of which may increase breast cancer risk.”
He also explained that what people should understand from this study is that keeping a healthy weight around midlife and beyond is essential. As a risk factor for breast cancer development obesity is modifiable. Although people cannot control genetic risk they can at least keep their weight under control. Maintaining a normal weight is a very good way of preventing cancer from occurring.
Image Source: The Guardian