Why is colon cancer rising in young? There is mounting evidence linking an unhealthy diet, one high in processed meat and fat, and low in fruits and vegetables to early-onset colorectal cancer. Other scientists have turned their focus to bacteria that live in the gut, also called the gut microbiome adults. Colon cancer risk is vastly lowered by following a healthy diet and daily exercise, avoiding processed food, and screening for those with genetic risks of colon cancer.