Insulin and breast cancer risk? Connection may be stronger than weight

January 25, 2015 | by Nicole White

When it comes to breast cancer risk, insulin levels may matter more than weight, new research has found.


Breast cancer risk New study indicates that insulin levels are more closely tied than weight to breast cancer risk.


The study from Imperial College London School of Public Health, published in the journal Cancer Research, indicates that metabolic health – not a person’s weight or body mass index – increases breast cancer risk in postmenopausal women. Although high insulin levels frequently occur in women who are overweight or obese, women at normal weights may have unhealthly insulin levels, as well, putting them at a perhaps unexpected increase in breast cancer risk. Likewise, some obese women may have normal levels of the hormone.

The study of insulin and breast cancer risk included 3,300 women without diabetes, 497 of whom developed breast cancer during the study’s eight years. The study analyzed weight, fasting insulin levels and insulin resistance. Insulin is a hormone that aids in using digested food for energy. An inability to produce insulin or use it properly leads to diabetes. Insulin resistance occurs when the body is unable to use insulin efficiently, resulting in hyperglycemia. The condition is often a precursor to type 2 diabetes.

The study found that women who were overweight or obese but not insulin-resistant did not have elevated risk of breast cancer compared to normal-weight women. However, normal-weight women with insulin resistance were at about the same risk of breast cancer as overweight women with insulin resistance. In the study, breast cancer risk doubled for women – both normal weight and overweight – who were insulin resistant.

“Fat is not inert,” said Courtney Vito, M.D., associate clinical professor at City of Hope, in an interview with HealthDay. “It is a metabolically active organ and we’ve known this from many other studies. There is much that experts still don’t know about fat.”

However, more research is necessary before the results can be considered conclusive, she said.

Allison DiPasquale, a fellow at City of Hope, suggested that future studies should more closely examine four subgroups: overweight women with and without insulin problems and normal-weight women with and without insulin problems.

Insulin resistance occurs in about 10 percent of normal weight women. However, the take-home message for women is to maintain a healthy diet and exercise regularly – the best defenses against developing insulin resistance.


Learn more about breast cancer treatment and breast cancer research at City of Hope.

If you have been diagnosed with breast cancer or are looking for a second opinion consultation about your treatment, find out more about becoming a patient by calling 800-826-HOPE (4673) or request a new patient appointment online.  City of Hope staff will explain what's required for a consult at City of Hope and help you determine, before you come in, whether or not your insurance will pay for the appointment.


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