Very overweight or obese teenagers are at twice the risk of developing bowel cancer in middle age compared with their slimmer peers, a study in the US has suggested.

Adult obesity has long been associated with an increased risk of bowel cancer.

Researchers in the US looked at the records of 240,000 men born between 1952 and 1956 who underwent a compulsory conscription assessment for the Swedish military during their late teens.

Obesity is commonly defined as a body mass index (BMI) of 30 or more, while people with a BMI of 25 or more are considered overweight.

Adult obesity has long been associated with an increased risk of bowel cancer

At the time of conscription the majority (81 per cent) of the participants they studied were of normal weight, but 1.5 per cent fell into the upper overweight group (a BMI of 27.5 to 30) and nearly one per cent were obese.

Analysis of the men’s health around 35 years later found885 had been diagnosed with bowel cancer, with scientists finding that those who were in the upper overweight men group had a 2.08-fold higher risk of developing the condition while for obese men there was a 2.38-fold greater risk.

The study, which is published in the journal Gut, was led by Harvard School of Public Health in Boston, Massachusetts.

Its authors acknowledged the study was purely observational and did not look at women, adding that further research is needed to investigate broader circumstances.

“Even with these limitations it is important to recognise the unique strengths of this study,” they added.