Teenagers who are very overweight may be much more likely to develop bowel cancer later in life, a new study has found.

It is already known that obesity in adulthood can increase the risk of this disease, however it is unclear what impact excess weight in adolescence may have. Swedish and US researchers decided to look into this further.

They monitored the health of almost 240,000 men who had been conscripted into the Swedish military between the ages of 16 and 20 years, from 1969 to 1976.

All underwent a health check-up when they enlisted and they were then monitored until 2010 - an average of 35 years - to see who had developed bowel cancer.

Bowel cancer is the second most commonly diagnosed cancer in both men and women in Ireland, with over 2,200 new diagnoses here every year.

At the time of their conscription, the majority of the participants were a normal weight, however, 5% were moderately overweight, 1.5% were very overweight and 1% were obese.

The study found that those with a body mass index (BMI) of between 27.5 and just under 30 when they enlisted in their teens, were twice as likely to develop bowel cancer later in life compared to those of a normal weight.

A person's BMI is worked out using a combination of weight and height. People with a BMI of between 20 and just under 25 are considered healthy, 25 to just under 30 is overweight and 30 or higher is obese.

The study also found that those who were obese in adolescence were 2.3 times more likely to develop bowel cancer later in life.

"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," the researchers commented.

They called for more research in this area.

Details of these findings are published in the journal, Gut.

If you would like to work out your BMI, click here