Feel full on fewer calories — it sounds like a gimmick. But in reality, it's true. You can feel full on fewer calories and at the same time lose weight and keep it off long-term.

To achieve and maintain a healthy weight, you have to follow an eating plan you can live with for a lifetime. That means no severe restrictions, no extreme hunger and no fads. Fortunately, choosing foods that are less concentrated with calories — meaning you get a larger portion size with a fewer number of calories — can help you lose weight and still control your hunger.

All foods have a certain number of calories within a given amount (volume). Some foods, such as desserts, have many calories in just a small portion. So in order to feel full, you'll need to eat larger quantities of these types of foods, which also means a larger number of calories. For example, just a half cup of mixed nuts has 438 calories. But a half cup of nuts isn't likely to leave you feeling full.

On the other hand, some foods — such as fruits, vegetables and whole grains — have more volume but fewer calories. In contrast to the 438 calories in a half cup of mixed nuts, a half cup of cooked green beans has just 19 calories, a half cup of cubed cantaloupe has 28 calories and a half cup of cooked whole-wheat spaghetti has 87 calories. So, you'll get more food, consume fewer calories and still walk away from the table feeling full.

Two factors play an important role in what makes food less calorie-packed and more filling:

• Water. Many fruits and vegetables contain water, which provides volume but not calories. Grapefruit, for example, is about 90 percent water and has just 39 calories in a half-fruit serving. Carrots are about 88 percent water and have only 52 calories in 1 cup.

• Fiber. High-fiber foods — such as vegetables, fruits and whole grains — not only provide volume, but also take longer to digest, making you feel full longer.

Changing lifestyle habits is never easy and creating an eating plan using this concept is no exception. The first step is knowing which foods are best.

• Vegetables. Most vegetables are low in calories but high in volume — salad greens, asparagus, green beans, broccoli, zucchini, just to name a few. Each vegetable serving is about 25 calories, and typical serving sizes are 1 cup raw, a half cup cooked or 2 cups leafy vegetables. Some vegetables are starchy — such as corn, potatoes, sweet potatoes and winter squash — and therefore contain more calories, about 70 calories a serving.

• Fruits. Practically all types of fruit fit into a healthy diet. However, some fruits are better choices than others. Whole fresh, frozen and canned fruit, without added sugar, have about 60 calories a serving. Unlike fruit juices and dried fruits, these types of fruit are higher in bulk because of water and fiber and are your best choices. A typical serving is a small- or medium-sized piece of fresh fruit or a half cup of sliced fruit.

• Carbohydrates. Most foods in this group are either grains or are made from grains, such as cereal, rice, bread and pasta. The best grains are whole grains because they're higher in fiber and other important nutrients. Whole grain means the bran and germ are left on the grain when it's processed. Examples include whole-wheat bread, whole-wheat pasta, oatmeal, brown rice and whole-grain cereal. Each serving of carbohydrate has about 70 calories. A typical serving is a half cup of grain, such as rice, pasta, barley or cereal, or one slice of bread.

• Protein/dairy. This includes foods from both plant and animal sources. The best choices are those that are high in protein but low in fat and calories, such as legumes — beans, peas and lentils, which are also good sources of fiber — fish, skinned white-meat poultry, fat-free dairy products and egg whites. Food in the protein/dairy group have about 110 calories a serving, which is about a half cup of legumes, 3 ounces of chicken or fish, or 1 cup of skim milk. Serving sizes will vary depending on the type of food.

• Fats and sweets. Eat sweets and high-fat foods in moderation since many of these foods are high in calories but low in volume. For example, just 1 tablespoon of butter has about 100 calories, and one standard-sized chocolate bar has about 225 calories.

Food Group and Serving Size List

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Starting a healthy diet that emphasizes fresh fruits and vegetables and whole grains makes room in your diet for some of your favorite foods in small quantities: a piece of chocolate cake or a small portion of ice cream, for example. When you're not feeling desperately hungry and deprived, as you might on some diets, you can enjoy a small portion of dessert without guilt.

Here are ideas to make this eating plan work for you:

• Increase the ratio of fruits and vegetables in your meals. For example, add blueberries to your cereal in the morning. Or top your pasta with sauteed vegetables and tomato sauce.

• Experiment with new foods and combinations. Try mango or peach slices on whole-wheat toast with a little peanut butter and honey. Toss some mandarin orange and peach slices into a salad. You may find some new tastes you love that fit within your eating plan.

• Start lunch or dinner with a broth-based, vegetable-filled soup or a large salad with a small amount of low-fat or fat-free dressing. These foods take longer to eat and will curb your hunger. Next, serve whole grains, an extra serving of vegetables and a serving of lean protein for your main course. By the time you get to dessert, you may not even have room for that cup of mixed berries topped with a spoonful of vanilla yogurt or ice cream.

By eating larger portions of foods less packed with calories, you'll squelch those hunger pangs and feel better about your meal, which will contribute to how satisfied you feel overall. So go ahead and have a large plateful of vegetable salad or a big bowl of broth-based soup. This is an eating plan you can live with.