Researchers examined the medical records of more than 250,000 individuals who were born in Denmark between 1930 to 1972. They found a marked increase in risk of bowel cancer in those with a higher BMI when they were young.
The study also found even if the weight is lost in adulthood, the damaging effects can potentially carry over into later years.
"BMI in childhood was associated with the later risk of bowel cancer, whereas there were limited indications of associations with rectal cancer," the report read, according to PA.
"These findings suggest that BMI in childhood may influence the risk of bowel, but not rectal cancer in adulthood."
A comparison between one 13-year-old boy of average height and weight and a second boy who was a similar height but weighed 5.9kg more showed the heavier child had a 9% higher risk of developing the cancer.
Results showed a similar pattern from ages seven to 12.
This is reportedly one of the first studies to make the association between childhood obesity and bowel cancer in adulthood.
On the NHS website, it states: "Taking steps to tackle obesity is important because, in addition to causing obvious physical changes, it can lead to a number of serious and potentially life-threatening conditions, such as breast and bowel cancer."
However, there were limitations to the study.
The authors stressed they “could not rule out” that the individuals studied had kept their weight on in later years.
The report, which will be presented at the European Obesity Summit in Sweden, said, according to PA: “Since no information is available on adult BMI in the present study, we cannot rule out that the results observed are due to continuation of large body size from childhood to adulthood.
“However, if this was the case we would expect to see an increasing risk of bowel cancer with increasing age in childhood, which is not the case.
“It is possible that exposure to excess weight already from childhood increases the risk of bowel cancer.”
In total, 257,623 individuals were examined as part of the study - of whom 2,676 were eventually diagnosed with bowel cancer.