Long-term obesity increases risk for colon, rectal cancer, study finds

March 17 (UPI) -- Being overweight or obese nearly triples a person's likelihood of developing colon and rectal cancer, with the risk increasing the longer they live with an unhealthy weight, a study published Thursday by JAMA Oncology found.

The risk for colon and rectal cancer rises 25% for every decade a person lives being overweight or obese, which is severely overweight, the data showed.

Those who live most or all of their lives at an unhealthy weight have a 2.5-fold higher risk for developing these potentially deadly cancers, the researchers said.

"The impact of overweight and obesity on risk of colorectal cancer is stronger than previously thought," study co-author Hermann Brenner told UPI in an email.

"Considering excess weight across a lifetime, as we did in our study, reveals a stronger association of excess weight with colorectal cancer risk," said Brenner, division head for clinical epidemiology and aging research at the German Cancer Research Center in Heidelberg.

Just over 40% of adults in the United States have obesity, meaning they are severely overweight, the Centers for Disease Control and Prevention estimates.

Although "multiple" could explain the relationship between weight and colon and rectal cancers, it is believed that those who are overweight or obese have chronic inflammation that may play a role in tumor growth, he said.

They are also at higher risk for Type 2 diabetes, which in turn makes them more likely to develop cancers, research suggests.

Previous studies have also linked diet with the health of the gut microbiome, the bacteria in the digestive tract that helps the body convert food to nutrients that has a significant influence on overall health.

Unhealthy, fattening foods are known to increase the risk for some colon and rectal cancers, while weight loss has been shown to reduce the risk for these diseases, according to previous studies.

For this study, Brenner and his colleagues analyzed body weight data on more than 5,600 German adults with colon and rectal cancers.

Collectively, these cancers are the third-most-common in the United States and are third-leading cause of cancer deaths nationally, according to the CDC.

To reduce the risk for these cancers, people must "prevent development of overweight and obesity in childhood, adolescence and young adulthood," Brenner said.

"Promoting a lifestyle with sufficient physical activity is a key aspect in this context," he said.