Healthy Body Size with Unhealthy Insulin Levels May Increase Colorectal Cancer Risk

Overweight and obesity increase the risk of colorectal cancer, possibly due to excess body fat leading to high levels of hormones that can spur the development of cancer cells. A recent study now suggests that individuals who appear to have a healthy body size but have high levels of the hormone insulin also face increased risk of colorectal cancer.

The study, published in PLOS medicine, was partly funded by World Cancer Research Fund.

The case-control study included almost 1,500 participants of the European Prospective Investigation into Cancer and Nutrition (EPIC). Half had developed colorectal cancer and they were matched to similar participants who had not developed cancer. The study used blood concentrations of the protein C-peptide as a marker of insulin levels, and BMI measurements to categorize individual's metabolic health. Researchers used the non-cancer comparison group’s C-peptide levels to determine a value they categorized as metabolically unhealthy.

Then everyone was separated into four groups: metabolically healthy/normal weight, metabolically healthy/overweight, metabolically unhealthy/normal weight, or metabolically unhealthy/overweight.

Compared to healthy weight individuals who were metabolically healthy — those who had normal levels of insulin — overweight individuals with high insulin levels were at a greater risk of colorectal cancer.  Those who were a healthy weight but had high insulin levels were also at a greater risk of colorectal cancer than people of the same weight but with normal insulin levels.

Among overweight individuals, those who were metabolically healthy had a lower colorectal cancer risk than metabolically unhealthy individuals. Similar associations were seen in this group when using waist circumference instead of BMI as the measure of body fat.

These findings suggest that insulin levels could also help identify individuals at risk of colorectal cancer, the authors write. Study limitation include the C-peptide level chosen as metabolically healthy: currently, there is no accepted clinical definition for using C-peptide level to diagnose hyperinsulinemia. 

Insulin is a hormone that controls the level of sugar in the blood and the amount of body fat that is stored. C-peptide is a protein found in generally equal amounts as the hormone insulin. 

AICR estimates that nearly half (47 percent) of US colorectal cancer cases could be prevented through healthy changes in diet, weight and physical activity.

Source: Neil Murphy et al. A Nested Case–Control Study of Metabolically Defined Body Size Phenotypes and Risk of Colorectal Cancer in the European Prospective Investigation into Cancer and Nutrition. PLOS Medicine. Published: April 5, 2016.

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    Published on October 5, 2016

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