Fiber is a substance found in vegetables, fruits, legumes and whole grains. Unlike carbs, fats and protein, fiber is not digested in your body, thus helping digestion and preventing constipation. Other benefits of dietary fiber are lowering cholesterol levels, controlling blood sugar and aiding in weight loss. Fiber-rich food makes you feel full faster and stay full longer. There are two types of fiber – soluble and insoluble. Soluble fiber dissolves and turns into gel during digestion, slowing the process and lowering cholesterol level. Sources of soluble fiber include oat bran, peas, seeds, beans, lentils, apples, citrus fruits, carrots and barley. Insoluble fiber adds bulk to the stool and aids in the movement of material through your digestive system. Good sources of insoluble fiber include vegetables, wheat bran and whole grains.

Most fiber is contained in the peel, seeds and membranes of vegetables and fruit, so, when possible, eat the whole apple instead of peeling it. The recommended daily intake of fiber is 30-38 grams for men and 21-25 grams per women. It's better to accompany a high-fiber diet with at least 8 glasses of water to help move fiber through your digestive system. Don't add a lot of fiber to your diet at once if you aren't used to eating it. Start slowly to give your digestive system time to adapt and this will help avoid unpleasant symptoms of eating too much fiber, such as intestinal gas and abdominal cramps.