ST. LOUIS — So you want to feel better, look better and be nicer? Eat more dietary fiber.

"Fiber has a major benefit in reducing obesity and constipation," said Dr. Mike Roizen, co-author of "You: The Owners Manual" and founder of RealAge.com, a popular health Web site.

While those factors alone can make you a better person, the overlooked benefit of fiber is that to get more, you need to eat healthful food.

"You're not only adding fiber to your diet, but you change from eating chips to eating fruit," he said. "You not only have the healthy food, but you get rid of the lousy food. It's like walking with a friend. Not only do you get the benefit of the walking, but you get the benefit of the friendship."

Fiber comes in two varieties, insoluble and soluble, said Dr. Charlene Prather, a gastroenterologist with SLUCare and St. Louis University School of Medicine.

• Insoluble relieves constipation by pushing waste material rapidly through your system. The result is you feel better. It's found in the indigestible parts of plants that we eat — grain husks, skins of fruits and vegetables, the brown in brown rice, outsides of beans, peas and berries. It's also called roughage or bulk.

• Soluble fiber often gets forgotten. But it's the one that lowers cholesterol and reduces the risk of heart disease and is associated with reversing obesity. Soluble fiber turns up generally in the pulp of fruits, vegetables, grains and beans. Rather than using stomach acids and enzymes to digest soluble fiber, your body uses bacteria, which digest it slowly. The slow digestive process keeps food in your stomach longer and deters your hunger longer — especially if you drink a lot of water on top of it.

Soluble fiber becomes a spongy, watery gel that moves through the system sponging up cholesterol that wants to get into your bloodstream.

Food labels generally say "fiber" because most fiber-rich foods carry both forms of fiber, although some foods carry more of one and less of the other.

Fruits have lots of each. The skin has the insoluble fiber while the pulp carries more soluble fiber. For example, a medium pear will have 5.1 grams fiber, a fifth of a woman's daily requirement of 25 grams of fiber and a sixth of the 30 grams of fiber men need. The daily requirements vary by a person's size, weight and age.

Unfortunately, people get only about half their daily fiber content, Prather said.

Supplements can compensate for a lack of fiber in the diet, Prather said. However, he prefers patients get fiber from a healthy diet. Supplements can be an excellent substitute. They're no longer the yucky, icky stuff you'd stir into something."

Still, she said, "A healthy diet has the vitamins and nutrients and things we don't understand. I recommend eating whole fruits and vegetables, but in this fast-paced life, it's sometimes not practical."

Jeannie Gazzaniga-Moloo, a spokeswoman for the American Dietetic Association, agreed that food sources are preferable because the best that a packaged supplement can offer is to be bundled with some vitamins.

"If a person were to bring more whole grains, fruits, vegetables and legumes into their diets, it's going to help boost the fiber content of their diet," Gazzaniga-Moloo said.

Some people stay away from high-fiber diets because of gas, Prather said. Gas comes from bacteria digesting increased volumes of soluble fiber. It takes a week or so for your system to adapt. To prevent gas, start increasing your fiber content slowly, Prather said. Diets high in red meat can make the transition challenging. The alternative is to stay away from friends and family for a week.

Prather said if you're going to load up on fiber anywhere, do it at breakfast. That means higher fiber cereals, bread and fruit. The effect can hold down your appetite through the day, she said.

She recommends getting five grams of fiber in your breakfast. But she stresses to read the labels. The fiber content of bread and cereal often doesn't stand up to marketing claims.

For example, while heavy, dark, dense loaves of bread claim to be high in fiber, the lighter, fluffy, whole grain, whole-wheat bread can have more fiber and fewer calories per slice.

Some cereals can provide a lot more than 5 grams of fiber in a bowl, she said, "But that tastes like cardboard." Sometimes, however, you can mix tasty cereal with high fiber cereal.

• When grandma makes that apple or peach pie, save the peels. Freeze them, pop them into a blender with some milk, yogurt or even apple cider and make a smoothie. Add a pinch of cinnamon to get an apple pie essence. Sweeten with a teaspoon of honey or Splenda.Switch yams for white potatoes or eat baked potatoes with the skin on rather than mashed potatoes with the skin removed. If you must mash, chop first with the skins on.Mix in or use whole-grain flour for cooking. Start to increase the amount of whole-grain flour in your recipes, even making homemade pasta or pie crusts. You might need practice, or you might find a blend that works, even for pasta. Whole-wheat flour also mixes with instant flour mixes such as Bisquick.• Use fiber supplements. This is one of the few nutrient supplements that actually works. Most food labels don't distinguish between soluble or insoluble fiber because most fiber-rich foods have both. But if your idea of vegetables is corn-fed beef and the hops in your Michelob, consider buying pills or powders. Dietitians don't like this, but even they admit that supplements are better than nothing.