While a larger waist may up the risk factor of breast cancer, BMI is the biggest contributing factor to this disease a new study finds.
A previous study revealed that body shape itself is an independent risk factor for breast cancer and suggested that a larger waist circumference ups the chances of developing the disease. Researchers of a new study found that while this may be true, a woman's BMI remains a bigger risk factor of breast cancer.
Abdominal obesity has been linked to a number of conditions including heart disease, type II diabetes, and breast and other cancers. Researchers previously suggested that having an "apple shaped" body, with weight concentrated in the chest and torso is riskier than having a "pear-shaped" body, with fat concentrated in the hips, thighs and buttocks.
To examine the authenticity of this theory, a team of American Cancer Society researchers looked into the health data of 28,965 women participating in the Cancer Prevention Study II. During an 11.58 years follow-up study, 1,088 study participants were diagnosed with invasive breast cancer. Though researchers did find a link between larger waist circumference and breast cancer, when BMI was adjusted this association disappeared.
"The message is that if you have a high BMI, regardless if you are pear or apple shaped, you are at higher risk of breast cancer," lead author Dr. Mia Gadet said in a press statement. "Most prior studies on this issue looked at BMI or at waist circumference, but had not looked at them together. This study brings some clarity to the association between obesity and risk of breast cancer."
Gadet hopes that the findings of this study help women concentrate on the important factors of breast cancer instead of worrying about other non-essential factors.
"We know being overweight, particularly when the weight gain happened during adulthood, is one of the important modifiable risk factors for breast cancer in post-menopausal women. This new data indicates it's not what shape you are, it's what kind of shape you are in that probably ought to be their focus," she said.
Many previous studies have also shown that overweight and obesity are associated with a modest increase in risk of postmenopausal breast cancer. This higher risk is seen mainly in women who have never used menopausal hormone therapy (MHT) and for tumors that express both estrogen and progesterone receptors.
The increased risk of postmenopausal breast cancer is thought to be due to increased levels of estrogen in obese women. After menopause, when the ovaries stop producing hormones, fat tissue becomes the most important source of estrogen. Because obese women have more fat tissue, their estrogen levels are higher, potentially leading to more rapid growth of estrogen-responsive breast tumors.
The current study was published in the April 2014 issue of Cancer Causes and Control.
