Among postmenopausal women who were normal weight, those who were metabolically unhealthy had a significantly increased risk for colorectal cancer compared with those who were metabolically healthy.
Even though poor metabolic health is usually associated with obesity, 30 percent of normal-weight adults are believed to be metabolically unhealthy worldwide, according to Liang.
Metabolic health is often assessed by measuring waist circumference, blood pressure, and levels of triglycerides, glucose, and high-density lipoprotein cholesterol (HDL-C, so-called "good" cholesterol) in the blood. People have metabolic syndrome if they have three or more of the following: elevated waist circumference, elevated blood pressure, elevated levels of triglycerides, elevated levels of glucose, and low levels of HDL-C. In this study, people were considered metabolically unhealthy if they had two or more of those factors excluding elevated waist circumference.
Liang and colleagues used data from 5,068 postmenopausal women enrolled in the Women's Health Initiative. All the women were classed as normal weight based on having a body mass index (BMI) from 18.5 kg/m2 to < 25 kg/m2; 33.7 percent of them were metabolically unhealthy.
During a mean follow-up time of 14.3 years, 64 of the 3,358 women who were classed as metabolically healthy were diagnosed with colorectal cancer and 50 of the 1,710 metabolically unhealthy women. After adjusting for numerous factors that affect colorectal cancer risk, the researchers calculated that women who were metabolically unhealthy had a 49 percent increased risk for colorectal cancer relative to those who were metabolically healthy.
The researchers also found that women with metabolic syndrome had a more than two-fold higher risk for colorectal cancer relative to those who were metabolically healthy.
"Our finding that normal-weight U.S. women who are metabolically unhealthy have an increased risk of colorectal cancer compared with those who are metabolically healthy highlights how important it is for women to be aware of their metabolic health status, which can be assessed using standard clinical tests," said Liang.
"Colorectal cancer is the third most commonly diagnosed cancer for women in the United States," she continued. "Recognition that normal-weight women who are metabolically unhealthy may have an increased risk for colorectal cancer could result in more timely use of preventive interventions and reduce the burden of this deadly disease."
According to Liang, the study had two main limitations. First, BMI and components of metabolic health were measured only at the time of enrollment in the Women's Health Initiative and possible changes over time could not be considered in the analysis. Second, the study population can be generalized only to postmenopausal women and not men or younger women.
The study was supported by a grant from the National Cancer Institute and the Youth Scholars Program of Beijing Normal University. Liang declares no conflicts of interest.
Article: Metabolic Phenotype and Risk of Colorectal Cancer in Normal-Weight Postmenopausal Women, Xiaoyun Liang, Karen L. Margolis, Michael Hendryx, Thomas E. Rohan, Erik J. Groessl, Cynthia A. Thomson, Candyce H. Kroenke, Michael S. Simon, Dorothy Lane, Marcia Stefanick and Juhua Luo, Cancer Epidemiology, Biomarkers & Prevention, doi: 10.1158/1055-9965.EPI-16-0761, published 1 February 2017.