There's nothing new about taking in fewer calories to lose weight. What is new in fighting the battle of the bulge is a diet weapon that reduces calorie intake by managing hunger. —

It's called "satiety." Not exactly a word that rolls off your tongue (pronounced "sa-TIE-atee"). It's a diet and nutrition buzzword for the state of feeling full, one word in a new vocabulary that includes terms such as "energy density," "sensory-specific satiety" and "volumetrics."

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If you've ever wondered why you fill up on a bowl of oatmeal but can eat three doughnuts before feeling satisfied, the reason is the comparative satiety levels of these foods.

Susanna Holt, PhD, developed a satiety index, reported in the European Journal of Clinical Nutrition. Taking 240-calorie portions of popular foods, she ranks them according to how they compare with a slice of white bread, which carries a rank of 100. Oatmeal has a high satiety level at 209, while a doughnut's rank is 68. Interestingly, a 240-calorie serving of boiled potatoes ranks highest at 323, but French fries score just 116.

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Two experts in nutritional research and weight loss spoke with WebMD about their very different approaches to helping people take in fewer calories and lose weight while eating nutritious, balanced meals, and without going hungry.

David L. Katz, MD, MPH, a medical correspondent on ABC's "Good Morning America," uses flavor management to turn off appetite, described in his new book, "The Flavor Point Diet: The Delicious Breakthrough Plan to Turn Off Your Hunger and Lose the Weight for Good."

The strategy of Barbara Rolls, PhD, author of "The Volumetrics Eating Plan and the Volumetrics Weight-Control Plan," substitutes foods that have fewer calories by weight compared with those that are energy-dense to feel full on fewer calories.

Turn Off Your Appetite

The variety of food we dieters eat may be doing us in. An abundance of different flavors at one meal overstimulates the brain's appetite centers so you overeat before feeling full, says Katz, who is director of the Yale Prevention Research Center in New Haven, Conn.

His Flavor Point diet is based on studies of sensory-specific satiety, or the tendency to feel full and stop eating when flavors are limited, and do just the opposite when flavors are varied.

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Research shows that different types of flavors, such as sweet, salty and sour, activate their own appetite centers in the brain. Katz says this is why you might feel full after eating a savory meal but still have room for dessert.

"Once you turn on an appetite center, you must eat until it registers fullness. If you turn on many centers at once, you must eat until they're all full."

Katz calls the point at which satiety is reached the "flavor point," and his diet plan restricts the types of flavors so you'll reach it without overeating. This isn't a cabbage soup type of diet. There's plenty of variety in the six-week plan, based on lean protein, whole grains, fruits and vegetables.

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In phase one of the diet, each day's meal plan has a flavor theme, such as pineapple, mint, pumpkin or spinach. For example, on spinach day, the day's menu features a spinach-feta omelet and toast or cereal for breakfast; two snacks of seven-grain crackers or baby carrots with spinach-yogurt dip; spinach and turkey chef's salad for lunch; and pasta fagioli with spinach marinara sauce, tossed spinach salad and mixed berries for dinner.

In phase two, each meal or snack has its own flavor theme, and by phase three you'll know how to restrict flavors without a plan.

Implementing this diet requires at least some basic skills in the kitchen. You'll find few processed convenience foods in the plan. Katz tells WebMD the problem is the combination of ingredients found in many foods on supermarket shelves.

"Some cereals contain more salt than potato or corn chips, and a popular pasta sauce has more sugar than chocolate ice cream topping. Yet we don't taste the salt in cereal because there's so much sugar that it masks the salt, just as the salt masks the sweetness of pasta sauce. We're dealing with stealth sugars and salts. They have a powerful influence on how much we eat, but they're below the radar screen."

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Katz's wife, Catherine, developed the plan's recipes, taking into account feedback from the couple's five children.

"The recipes have a strong French and Mediterranean influence, they're family friendly, provide perfect nutrition, and they're really delicious," Katz says. "We've always eaten this way, and we never have to count calories or worry about our weight."

Feeling Full Faster

Energy-dense foods pack a big calorie wallop in a little package. Think truffles or battered, deep-fried calamari. Energy density is a measure of calories per gram. Rolls, who is the Guthrie Chair of Nutritional Sciences at Pennsylvania State University in Pittsburgh, has studied how energy density affects satiety. "Satiety," she says, "is the missing ingredient in most weight loss programs."

Her volumetrics plan is based on eating balanced meals in which most of the calories come from foods with high volume and low energy density. For example, compare raisins (dried grapes) with fresh grapes. After eating one-fourth cup of raisins, you'd probably keep eating, but would you consume more than 1 3/4 cups of grapes? Both servings have 110 calories, but the grapes are plumped up naturally with water.

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Water is a key ingredient in volumetrics. Not the water you drink with a meal. Studies show it doesn't influence satiety. But the water in fruits and vegetables or in a broth-based soup swell the volume and make you feel full faster.

Rolls advises choosing foods in proportions recommended in the Food Guide Pyramid and modifying calorie intake on the basis of the following four levels of energy density.

Very Low: Most fruits and vegetables, skim milk and broth-based soups. Eat as much as you like.

Low: Many cooked grains; cereals with low-fat milk; low-fat meats, beans and legumes; low-fat mixed dishes; and salads. Eat relatively large portions.

Medium: Includes meats; cheeses; high-fat mixed dishes; salad dressings; some snack foods. Eat in moderation.

High: Includes crackers; chips; chocolate candies; cookies; nuts; butter; and full-fat condiments. Control portions carefully.

One strategy for filling up faster is to have broth-based soup or a big, low-calorie density salad as a first course.

"Our studies show they do reduce subsequent intake in the meal," Rolls says. Don't cheat and scarf down a salad loaded with cheese, ham and indulgent dressing. "If your salad is high in calorie density, it's worse. You don't compensate later."

Emotional and Social Eating Triggers

How does understanding satiety help the person who overeats in social situations or in response to stress?

"Knowledge empowers them," Katz says. "No matter how stressed or unhappy you are, there's a limit to how many apples, carrots or raw almonds you're going to eat but not the candy corn or potato chips. It's the processed foods that get the better of us."

There's an interaction between emotional triggers, social triggers and the kinds of foods people choose, he says. Being savvy about sensory-specific satiety enables you to choose comfort foods wisely.

"I have a house full of wholesome foods," Katz says. "If I'm eating for emotional reasons, I have a much greater ability to control portions than does someone whose house is booby-trapped."

"If people really have a problem with emotional eating, they need professional help. It may be an underlying problem. Satiety may not matter that much if you're eating for emotional reasons."

Satiety can, however, help people avoid "mindless eating" in front of the TV or at social gatherings. One strategy is to get in the habit of periodically asking yourself, "On a scale of 1 to 10, how hungry am I now?"

The problem of social eating is often compounded by alcohol plus the availability of palatable, energy-dense, varied foods served in large portions.

"If you're eating out occasionally, it's OK to treat yourself," Rolls says. "But if you eat out a lot, you need some strategies. Decide up front if you'll order an appetizer instead of an entrée or split meals with someone.

"In a survey, about 70 percent of people said they eat everything in front of them whether they want it or not. If you rely on a food preparer to give you the right amount of food, you're in trouble."

Rolls offers one last tip, based on her recent study published in the American Journal of Clinical Nutrition. Reducing portion size and energy density by 25 percent is the key. For example, instead of eating two slices of pizza, lower the energy density by substituting vegetables for some of the cheese, and eat just 1.5 slices.

"Slight reductions in portion size and energy density combined help people lose weight."

By Leanna Skarnulis, reviewed by Louise Chang, MD

SOURCES: Holt, S. European Journal of Clinical Nutrition, September 1995, vol 49: pp 675-690. Rolls, B. American Journal of Clinical Nutrition, January 2006, vol 83: pp 11-17. David L. Katz, MD, MPH, author, The Flavor Point Diet: The Delicious Breakthrough Plan To Turn off Your Hunger and Lose the Weight for Good; director, Yale Prevention Research Center, New Haven, Conn. Barbara Rolls, PhD, author, The Volumetrics Eating Plan and The Volumetrics Weight-Control Plan; Guthrie Chair of Nutritional Sciences, Pennsylvania State University, Pittsburgh.