The exact causes of colon and rectal cancer are not known, but risk appears to be associated with genetic, dietary, and lifestyle factors. Those with a personal or family history of colon cancer or polyps are at a higher risk as are those with ulcerative colitis, a form of inflammatory bowel disease, and immunodeficiency disorders. A rare inherited disease called familial adenomatosis or polyposis causes benign polyps to develop early in life and causes cancer in almost all affected persons unless the colon is removed. Risk also increases with age and with the occurrence of cancers in other parts of the body. High fat and meat diets are a risk factor, especially combined with minimal fruit, vegetable, and fiber intake. Lifestyle factors include cigarette smoking, obesity, and a sedentary lifestyle.