Being “thin on the outside” but having an unhealthy lifestyle increases bowel cancer risk, according to a study.
Writing in the journal PLOS medicine, researchers said people who maintain a healthy weight but have high insulin levels are at a greater risk of bowel cancer than those of the same weight with normal insulin levels.
Similarly, overweight people who have high insulin levels are at a significantly greater risk of bowel cancer than those who have normal levels.
Insulin is a hormone that controls the level of sugar in the blood and the amount of body fat that is stored.
Researchers said insulin levels should be assessed, as well as body mass index (BMI), to determine someone’s risk of bowel cancer and provide 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.
However nearly half (45%) of UK bowel cancer cases could be prevented through healthy lifestyle changes.
Previous 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.
“These interesting new findings allow us to identify the groups of the population who are at the greatest risk of bowel cancer,” said Dr Panagiota Mitrou from the World Cancer Research Fund, which funded the study.
“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.”
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Dr Marc Gunter, study scientist from the International Agency for Research on Cancer (IARC), 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.”
Gail Curry, head of health promotion and training for Bowel Cancer UK, said: “We welcome studies that help us understand more about this preventable disease. It adds to the evidence that having a healthy diet and being physically active reduces your risk of bowel cancer.
“Early diagnosis is also key to survival of bowel cancer, and people should be aware of symptoms such as bleeding, a change in bowel habit, sudden weight loss, abdominal pains and lumps, and extreme tiredness.”
Dr Helen Webberley, the dedicated GP for Oxford Online Pharmacy, added: “Any cancer has a better outcome if caught early, so any changes in bowel appearance or frequency should never be ignored.
“It’s not always an easy topic to broach but the advice is clear: ‘don’t die of embarrassment’.”