Add This Secret Weapon to Your Diet Pla

Screw self-restraint. We've got a better weight loss success plan: Stuff yourself silly. There's a way to fill your mouth and your stomach without doing the same to your yoga pants. It's called fiber, and if you still think of it as something Grandma stirs into her OJ to stay regular, you need a serious update. "Fiber is the secret to losing weight without hunger," says Tanya Zuckerbrot, R.D., author of The F-Factor Diet. One U.S. Department of Agriculture study found that women who increased their daily fiber intake from 12 grams to 24 absorbed 90 fewer calories per day than those who ate the same amount of food but less fiber. Do nothing to your diet other than add more of the rough stuff and you will lose nine pounds in a year, effortlessly. Here's how this wonder substance works--and why you'd have to be nuts to let a day pass with less than your recommended 25 grams. Learn how snacking on the right foods can help you lose weight, too, in "Snack Yourself Slim" and WH's "125 Best Packaged Foods."

Fiber 101
What is it, exactly, that we're asking you to shovel into your body? Fiber is the indigestible part of a plant. It's in fruits, veggies, whole grains, nuts, legumes, and beans. Now that the fiber trend is catching on, you'll also find it added to yogurt, soy milk, pasta, and more. Other foods pause to pay a toll along your gastrointestinal highway, but fiber zips through E-ZPass style because your body can't digest it. Like seat fillers at the Oscars, fiber fills a void and then vanishes when something better takes its place.

You've probably heard of the two kinds of fiber, soluble and insoluble. Soluble fiber tends to hide inside foods--the flesh of apples, the grain of rice inside the hull. It's what gives cooked veggies their soft, mushy quality. In your stomach, soluble fiber binds with liquids to form a gummy gel that makes you feel full as it slows digestion, letting your body absorb more nutrients from the rest of your food.

Insoluble fiber is what most octogenarians are after. It bulks up as it absorbs liquid in the stomach; the bulk pushes waste down and out of your system. Insoluble fiber is usually found in the skins and outer parts of foods, and it's what gives many their tough, chewy texture. "Think of insoluble fiber as a broom," Zuckerbrot says. "Basically, it speeds up the passage of material through your digestive tract and sweeps out all the toxins in your body." Translation: Hello, fiber; goodbye, constipation.

As long as you're eating natural foods, you'll reap the belly-filling benefits of both kinds of fiber. By taking up space in your stomach, fiber foils overeating by making you feel too stuffed to keep snacking. And while you're enjoying the satisfaction of a full stomach, you can gloat over the fact that it likely took fewer calories to achieve that feeling: Foods that pack a lot of fiber can help lower your carb intake. If you're noshing on cereal with 44 grams of carbs per serving, but 10 of those carb grams come from dietary fiber, your body will absorb only the 34 grams of nonfiber carbs. The result: High-fiber fare can help you stay out of the spike-and-crash cycle some high-carb foods can create.

Diamonds in the roughage
The only bad thing about fiber is that most of us don't get enough of it. "More research is showing that Americans' intake of fruits and vegetables remains below recommended levels," says Sari Greaves, R.D., a spokesperson for the American Dietetic Association. Remember that RDA of 25 grams? The average woman squeaks by on about 14, according to the Agricultural Research Service. Too many of us chow down on fiber-empty grub like chips and soda. Fiber-rich foods deliver more bang for their bulk: They tend to be the most nutrient-dense, which matters if you're cutting calories.

Now that fiber comes in everything from yogurt to grape juice, it might be tempting to let fiber-added goods fill the gap. But while those products have their place, they shouldn't be your go-to source. "It's always better to get your fiber from whole foods," Greaves says. Supplements and add-ins don't have the same nutritional benefits as whole foods.

Some easy ways to sneak in natural fiber:
Add a small salad to your dinner.
Swap out your white rice for brown.
Toss kidney beans or chickpeas into your soup.
Switch to cereal with at least five grams of fiber per serving, or go 50-50 with your usual cereal and a higher-octane variety.
Eat high-fiber fruit like raspberries with light whipped cream for dessert. But before you start eating kidney beans by the truckload, remember that most experts recommend upping your fiber intake gradually. A sudden increase can leave you bloated and gassy--side effects sure to sabotage your efforts to look good in a miniskirt. "If you're getting about 10 grams a day and suddenly shoot up to 25, you're going to experience a little discomfort," says Carolyn Williams, a nurse practitioner at the Mayo Clinic in Scottsdale, Arizona. "You're just not used to that bulkiness."

A better strategy: Start small and build. And drink plenty of H2O--without it, you may find yourself in even more of a bind (pun intended). Don't go overboard, either. Fiber's benefits start to wane once you hit 50 grams per day. "It doesn't happen often," Greaves says, "but you can max out. Too much fiber can compromise the absorption of vitamins and minerals."

If you're not getting enough fiber through food alone, supplements can make up the difference. "Fiber got a bad rap in the '70s because there were all these horrible concoctions--twigs and branches and wheat germ," Williams says. "Now we can get it without even tasting it. Fiber from supplements makes people full, and it's very healthy for you." Sounds better than tree bark, doesn't it?

Beyond All-Bran
Metamucil doesn't make your mouth water? Here are tastier ways to get fast fiber. All-natural
1 medium avocado, 13.5 grams
1 cup of edamame, 8 grams
1 cup of raspberries, 8 grams
1 mini bag popcorn, 4 grams
1/2 grapefruit, 2 grams

Grab and go
1 Gnu Foods Banana-Walnut Flavor & Fiber bar, 12 grams
1 Thomas's Light Multi Grain English muffin, 8 grams
5 Reese's sugar-free mini peanut butter cups, 6 grams
1 Hostess Coffee Cakes 100-Calorie pack, 5 grams
1 Lean Pocket (Whole Grain Ham & Cheese), 4 grams

Fiber's Foes
A roughed-up diet reduces more than just your muffin top. It may also cut your risk for:

Diabetes Eat tons of cereal fiber and whole grains and you'll lower your odds for type 2, reports a study in the Archives of Internal Medicine.

Breast and colon cancer In one study, a fiber-rich diet heavy on whole-grain breads and cereals cut odds of breast cancer. Other studies show that eating more fibrous foods, especially beans, may ward off colon cancer.

Heart disease A study in The American Journal of Clinical Nutrition found that people on a high-fiber diet had lower levels of C-reactive protein (CRP), often regarded as a risk factor for heart disease.