A large study suggests that premenopausal women with a large amount of abdominal fat (called visceral adiposity) have a higher risk of hormone-receptor-negative breast cancer than women with less abdominal fat.
Other studies strongly suggest that overweight or obese women have a higher risk of being diagnosed with breast cancer. Much of that research has looked at postmenopausal women and has linked being overweight or obese to a higher risk of being diagnosed with hormone-receptor-POSITIVE breast cancer. Researchers don't completely understand why extra weight seems to be associated with higher hormone-receptor-positive breast cancer risk. One possible reason is that extra body fat can increase estrogen levels, and estrogen can promote the growth of hormone-receptor-positive breast cancers.
People who aren't overweight or obese can still have a large amount of fat in their abdominal cavities. Some people seem more likely to have this problem. Abdominal fat is commonly called "pot belly" or "beer belly." Rather than looking at links between breast cancer risk and being overweight or obese, this study looked for links between visceral adiposity and breast cancer risk in premenopausal women.
The researchers looked at the records of 45,799 premenopausal women participating in the very large Nurses' Health Study. They tracked the women's visceral adiposity and breast cancer diagnoses.
There are two ways to measure visceral adiposity:
- waist circumference: basically the same as waist size
- waist-to-hip ratio: a comparison of waist circumference to hip circumference; if waist circumference is 30 inches and hip circumference is 36 inches, waist-to-hip ratio is 30 divided by 36, or 0.83
The researchers looked at the waist circumferences and waist-to-hip ratios of the 620 women in the study who developed breast cancer. There was no clear difference in overall breast cancer risk (either hormone-receptor-positive or hormone-receptor-negative) between women with waist circumferences and waist-to-hip ratios in the highest 20% compared to those in the lowest 20%. Still, when they looked specifically for links between visceral adiposity and hormone-receptor-negative breast cancer the researchers found:
- women in the highest 20% of waist circumferences were nearly 3 times (2.75 times) more likely to be diagnosed with hormone-receptor-negative breast cancer
- women in the highest 20% of waist-to-hip ratios were nearly twice (1.95 times) as likely to be diagnosed with hormone-receptor-negative breast cancer
The researchers aren't sure how to explain this suggested link between visceral adiposity and hormone-receptor-negative breast cancer. Since hormone-receptor-negative breast cancers usually don't respond to estrogen, increased estrogen levels related to the abdominal fat doesn't explain the link. The researchers think insulin and insulin receptors, which can affect breast cancer cell growth, may be playing a role.
Although you can have excess abdominal fat and technically not be overweight or obese, these issues often go hand and hand. While you can't control your genes, you can take steps toward a healthier lifestyle by eating healthy food, exercising regularly, and maintaining a healthy weight. All of this helps keep your breast cancer risk as low as it can be. Visit the Breastcancer.org Lower Your Risk section to learn more.