After menopause, unhealthy insulin levels may predict breast cancer risk even more than excess weight, new research suggests. The study was published in Cancer Research.
To assess insulin’s role in breast cancer risk, Marc Gunter, Ph.D., an associate professor of cancer epidemiology and prevention at the Imperial College London School of Public Health, and colleagues studied 3,327 women without diabetes, 497 of whom developed breast cancer over eight years. The authors analyzed information on their weight, fasting insulin levels, and insulin resistance.
The researchers found that high fasting insulin levels doubled the risk of breast cancer, both for overweight and normal-weight women. In addition, women who were overweight and insulin-resistant had an 84 percent greater risk of breast cancer than overweight women who weren’t insulin-resistant.
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“The women who are overweight but who do not have metabolic abnormalities (as assessed by insulin resistance) are not at increased risk of breast cancer compared to normal-weight women,” Gunter told HealthDay. “On the other hand, normal-weight women with metabolic abnormalities were at approximately the same elevated risk of breast cancer as overweight women with metabolic abnormalities.”
The new findings suggest “that it is metabolic health, and not overweight per se, that is associated with increased risk of breast cancer in postmenopausal women,” he said.