Dr. Heyns - Diverticulitis, Risk Factors

These factors may increase the pressure on the wall of your colon:

Aging.
As you age, the outer muscular wall of your colon thickens, causing the inside passageway to narrow. The narrowing increases pressure in your colon and makes it more likely that pouches will form. Thickening of the outer wall also makes it more difficult for your colon to move waste through to your rectum. This means waste stays in your colon longer, becoming harder and dryer and exerting additional pressure on weak areas when the muscles of your colon try to move it along.

Too little fiber.
Diverticulitis is rare in countries where people eat a high-fiber diet that helps keep stools soft. But it's common in industrialized nations, where the average diet is high in refined carbohydrates and low in fiber. In fact, diverticular disease emerged after the introduction of steel rolling mills, which greatly reduced the fiber content of flour and other grains. The disease was first observed in the early 1900s, around the time processed foods became a mainstay of the populations diet. Too little fiber contributes to small, hard stools that are difficult to pass, which increases pressure in your colon.