Diverticulosis is caused by the herniation of the colon mucosa through the muscular layer of the colon. This produces a small saclike swelling in the colon wall (diverticula). The most common locations for diverticuli are in the sigmoid and distal colon. The exact reason for the herniation is not known. Up to 20% of the general population is affected with diverticulosis. Older individuals tend to have diverticuli more often than younger individuals. Up to 50% of individuals at age 50 will have them. Individuals who eat a low-fiber diet are much more apt to form diverticula.