Teenagers who are significantly overweight appear to have twice the risk of developing colorectal cancer in middle-age compared with teens of normal weight, according to a study led by Harvard T.H. Chan School of Public Health researchers.

Elizabeth Kantor, lead author and research fellow in the Department of Epidemiology, and colleagues tracked the health of about 240,000 Swedish men over a period of years; 885 of the men developed bowel cancer. The results showed that obese teens who had a BMI of over 30 had a 2.38 fold higher risk of developing bowel cancer. The authors speculated that high levels of systemic inflammation in overweight teens may contribute to the increased risk.

The study was published May 25, 2015 in the BMJ’s journal Gut. Other Harvard Chan School authors included Lisa Signorello, adjunct associate professor of epidemiology, Edward Giovannucci, professor of nutrition and epidemiology, and Katja Fall, visiting scientist in the Department of Epidemiology.

Previous studies looked mostly at weight and colorectal cancer in adults. This is the first large-scale investigation looking at the link between excess weight in teens and colorectal cancer risk in adulthood.

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