What does dietary fiber do in the body?

Fiber is good 4 you. Fiber, of both water soluble and water insoluble variety, provides health benefits. Fiber accelerates how quickly food transits through the gut. Fiber adds bulk to stool and improves bowel regularity. Fiber can be used as an adjunct to weight loss by filling you up without excess calories, and in so doing restricting fat intake. But too much fiber can make you gassy and increase stool volume.
See below. soluble fiber can slow down the stool transit and absorb water in the case of loose stools or diarrhea. Insoluble fiber, which is not digested well, increases the bulk of the stool as well as the transit time and helps in people with constipation and diverticular disease.
Feed the colon. The cells lining the colon obtain much of their nutrition from the break down of fiber. A short answer to some fairly complex processes.