Excerpted from http://www.mayoclinic.com/health/high-fiber-foods/NU00582
“All calories are not the same. Each ounce of food is not the same in the way your body responds. Use foods full of fiber for more benefit in losing weight.
Fiber is the structural part of fruits, vegetables, and grains that your digestive system cannot digest or break down. Increasing fiber in the diet can be an important factor in improving your overall wellbeing. For instance, bran has been found to reduce blood sugar and to lower cholesterol. Bran has become a friend to the dieter as well, because it is effective as part of an overall weight control program. Fibrous foods give you a sense of fullness because of the bulkiness of fiber. Fiber rich foods require more chewing. So eating takes longer and you feel satisfied sooner. Fiber has almost no calories because your intestinal system does not digest it.
Fiber binds with fats of which contain calories then carries them through the colon and keeps them from being absorbed. Each gram of fiber can flush with it 7 calories approximately. So the average American, who eats only 12 grams of fiber in a day, only flushes about 84 calories from their day. Health standards recommend eating 35 grams of fiber each day, thus flushing 245 calories. If you increase your fiber to 45 grams of fiber per day you will flush 315 calories. So, if you eat a 1,200 calorie diet, you can flush 1/4 of those calories simply by adding in food that are high in fiber at each meal, or supplement the fiber into your meals.
You must increase your fluid intake as well. Drink water. Since dietary fiber is somewhat sponge like, it absorbs water. Additional amounts of water are helpful in pushing the fiber along its course.
Dietary fiber can help your colon and is an important part of the management of diverticulosis and irritable bowel syndrome. It speeds the progress of food passing through your digestive tract and promotes regular bowel movements. The increased ease of stool passage keeps the intestinal muscles in good shape and prevents the sluggishness that leaves stool sitting in the colon for long periods of time. This may help to prevent diseases of the bowel, including the formation of polyps, which, when left unattended, may lead to bowel cancer. Furthermore, fiber may bind with or dilute cancer causing agents in some foods and help push them out of the body rather than allow them to be absorbed into the intestines.
Foods vary greatly in the amount of fiber they provide. Milk and its products, fats, meats, poultry, fish, and eggs contain NO fiber at ALL. The richest source of fiber is whole grains. But nearly all the grains we eat today are highly processed, and break down quickly in our systems to sugar, which then gets carried away by insulin to be stored for future use in our fat cells. And too many of us have too much stored. Your best sources of fiber are nutty whole grains: brown and wild rice, stonecut oatmeal and breads with the first ingredient listed as whole wheat flour, along with raw fruits and vegetables. White rice, potatoes, and white breads are low in fiber, and quickly convert to sugars when eaten.
Aim for 25 to 35 grams of fiber daily, but work up to it as your system tolerates it. If you are currently consuming little or no fiber in your diet, make the change gradually. Don’t shock your intestinal tract.
Introducing large amounts of fiber too abruptly may result in cramping, increased gas, or even diarrhea. If any of these occur, cut back on the portions of fiber you are eating, then gradually increase the amount until you can tolerate 35 grams per day, which will provide you with your fiber requirement.”