A new study suggests that teenage obesity is linked to a greater risk of bowel cancer later in life.

The study, published in the journal Gut, followed 239,658 Swedish men for 35 years. The young men were conscripted into the military aged 16 to 20 years old.

The analysis, led by Orebro University Hospital in Sweden and Harvard University, showed overweight teenagers went on to have twice the risk of bowel cancer. The figures were even higher in obese teens.

Teenage boys who become very obese may double their risk of getting bowel cancer by the time they are in their 50s.

The study and researchers were funded by the National Cancer Institute, Harvard School of Public Health, Örebro University and the UK Economic and Social Research Council (ESRC).

The World Cancer Research Fund said the link between obesity and cancer was “strong”.

Bowel cancer is the third most common cancer in the world, with nearly 1.4 million new cases each year.

Processed red meat and abdominal fat have been linked to the disease.

The overwhelming majority of participants were a normal weight, but 6.5% were overweight and 1% were obese.

There were 855 cases of colorectal cancer in the study.

However, the results showed not all weights were affected equally.

Those who were obese were 2.38 times more likely to have developed a bowel tumor.

The study said: “Late adolescence marks the transition from childhood to adulthood and is a period of accelerated growth, especially among men, thus this period may represent a critical window.

“It is important that we understand the role of exposures in childhood and adolescence in the development of colorectal cancer.

“In fact, the strong association observed between adolescent obesity and early-to-mid-life colorectal cancer [CRC], coupled with the increasing prevalence of adolescent obesity, may shed light on the increase in colorectal cancer incidence among young adults.”

Being obese and having long-lasting (chronic) signs of inflammation in the body as an adult have been linked to increased bowel cancer risk. Adolescents with “high” levels of inflammation were more likely to develop bowel cancer than those with “low” levels.

The marker (or sign) of inflammation the researchers had information on was the erythrocyte (red blood cell) sedimentation rate, or ESR. This measurement increases when there is inflammation.

However, few of the studies have assessed the effect of obesity in adolescence specifically, and none have been said to look at the impact of inflammation in adolescence.

The researchers concluded that, “late-adolescent BMI and inflammation, as measured by ESR, may be independently associated with future CRC risk”.