Most fruits and vegetables are high in fiber. Dietary fiber has complex carbohydrates from plats that humans lack the enzymes to digest. Fiber passes through the body undigested, keeping your digestive system clean and healthy, easing bowel movements, and flushing cholesterol and harmful carcinogens out of the body. There is no fiber in meat, dairy, or sugar. Refined or “white” foods, such as white bread, white rice, and pastries, have had all or most of their fiber removed.