A projected rise in young colon cancer sufferers is based on unhealthy eating and other lifestyle factors.

Colon cancer among people under 34 may nearly double over the next 15 years, raising new concerns about how to fight one of the most common and deadly cancers.

The rise in incidence in the younger population - blamed on lifestyle choices - goes against a long-running decline in colon cancer among people over 50.

The decline was largely due to tougher screening and regular colonoscopies.

The projected rise in the young is based on unhealthy eating and other lifestyle factors, said findings in the Journal of the American Medical Association Surgery.

By 2030, more than one in 10 colon cancers and nearly one in four rectal cancers will be diagnosed in patients younger than 50, said the study conducted by researchers at The University of Texas MD Anderson Cancer Center.

The projected increase was based on factors including obesity, lack of physical activity and a Western diet, which could "exponentially" increase risk, it said.

"We're observing the potential real impact of colorectal cancer among young people if no changes are made in public education and prevention efforts," said principal investigator George Chang.

Nearly 137,000 people will be diagnosed with colon cancer in the United States this year, and more than 50,000 will die of the disease, according to statistics in the article.

Colon cancer is the third most common cancer among men and women, and the third leading cause of cancer death.

The study was based on a registry that included more than 393,000 patients with confirmed colon cancers between 1975 and 2010.

Researchers found that the annual incidence rate for these cancers in patients under age 34 was "increasing across all stages of disease."

The study stopped short of recommending a change to screening guidelines, but said doctors should be aware of symptoms that might otherwise be dismissed in younger people.

Copyright AAP 2014.