Being thin on the outside but unhealthy on the inside increases bowel cancer risk

22 September 2016

People who appear slim but have high insulin levels may have an increased risk of bowel cancer, a study partly funded by World Cancer Research Fund has found for the first time.

The study, published in PLOS medicine, found that those who were a healthy weight but had high insulin levels were at a greater risk of bowel cancer than people of the same weight but with normal insulin levels1.

Similarly, overweight individuals who had high insulin levels were at a significantly greater risk of bowel cancer than overweight individuals who had normal insulin levels.

These findings suggest that insulin levels could be assessed as well as body mass index (BMI) to determine someone’s risk of bowel cancer. This could help identify those with the greatest risk of bowel cancer, who would benefit from targeted interventions to control their insulin levels.

Bowel cancer is the fourth most common cancer in the UK and a major cause of cancer-related death, killing over 16,000 people a year. This number needn’t be so high as bowel cancer is one of the most preventable cancers. Nearly half (45%) of UK bowel cancer cases could be prevented through healthy lifestyle changes2. World Cancer Research Fund’s research shows that a number of lifestyle factors increase the risk of bowel cancer including being overweight or obese, eating red or processed meat and drinking alcohol.

Insulin is a hormone that controls the level of sugar in the blood and the amount of body fat that is stored.

Dr Panagiota Mitrou, Director of Research Funding at World Cancer Research Fund, said:

“These interesting new findings allow us to identify the groups of the population who are at the greatest risk of bowel cancer.

“World Cancer Research Fund’s analysis of research has found strong evidence that obesity increases risk of bowel cancer.

“It’s very important to have a healthy diet and exercise regularly. This won’t only help reduce your risk of bowel cancer but also of a number of other cancers.”

Dr Marc Gunter, study scientist from International Agency for Research on Cancer (IARC), France, said:

“These results show for the first time that bowel cancer risk is associated with elevated insulin levels among lean people, as well as those with obesity. High insulin levels are common in obese individuals but less so in leaner people. We don’t know why the lean individuals had raised insulin levels but it could be due to poor diet or sedentary behaviour.”

“Measuring insulin levels could be used alongside BMI as a new tool for assessing bowel cancer risk to better determine who is at the greatest risk and requires greater monitoring.”


For more information contact:

Lucy Eccles, International Communications Officer, WCRF on 020 343 4235 or

Notes to editors:

About World Cancer Research Fund

For the past 25 years, World Cancer Research Fund has been the UK’s leading charity dedicated to the prevention of cancer through diet, weight and physical activity. By funding and supporting research, developing policy recommendations and providing health information, we have ensured that people can make informed lifestyle choices to reduce their risk of developing a preventable cancer. As we look forward to our next 25 years, our scientific research ensures that we will continue to have the latest and most authoritative information at our fingertips, all underpinned by independent expert advice.

Our analysis of global research shows that a third of the most common cancers are preventable through a healthy diet, maintaining a healthy weight and regular physical activity.

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About the research

737 participants in the EPIC cohort study who developed bowel cancer were matched with 737 controls that did not developed bowel cancer. In each participant, C-peptide levels were measured as a marker for insulin levels; metabolically healthy individuals had a C-peptide level below the first tertile of C-peptide and metabolically unhealthy individuals had C-peptide concentrations above the first tertile. BMI was used to classify if they were overweight (BMI>25 kg/m2) or a healthy weight.

1 Murphy N, Cross AJ, Abubakar M, Jenab M, Aleksandrova K, Boutron-Ruault M-C, et al. (2016) 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 (EPIC). PLoS Med 13(4): e1001988. doi:10.1371/journal.pmed.1001988