Soluble fiber dissolves in water and so it becomes a gel in your stomach after you eat foods like grains (cereals, breads, pasta and rice), fruits and vegetables. Soluble fiber may help with weight loss as it makes you feel full longer, and research has shown it also may help lower blood cholesterol and blood sugar levels. Good sources of soluble fiber include oatmeal, oat bran, barley, dried beans and legumes, and citrus fruits. Insoluble fiber, on the other hand, remains unchanged by its passage through the stomach and intestines. It tends to add bulk to the stool and speed up the passage of material through the digestive tract. It has been found to reduce the risk of colon cancer and diverticular disease. Good sources of insoluble fiber include wheat bran, whole grain cereals, and fruit and vegetable skins.