Experts say the real reason behind the success, and ultimately the failure, of many weight loss diets is that their limited variety of foods and flavors makes people so bored with the food that they eat less and lose weight. Unfortunately, people eventually get so bored with the food that they give up the diets, gorge on the foods they've avoided and regain the weight they lost.

One new diet suggests that people should limit the variety of flavors so they eat less, without restricting total variety so much that we refuse to continue. The �Flavor Point Diet� recommends using one flavor for your food each day. For example, lunchtime tuna could be flavored with lemon and dinner that same night could feature chicken flavored with lemon. The next day, lunch could be tomato soup and dinner could be pasta with a tomato-based sauce. The purpose is to give the food enough flavor to be enjoyable, yet to repeat the flavor enough so that the dieter will not eat too much of it. It also could change frequently enough from day to day that it would not make a dieter give up altogether.

Several studies show that when people are repeatedly exposed to a food with a single flavor, their ratings of its taste drop. They enjoy it less and eat smaller amounts of the food. Other foods that seem similar also become less desirable, but appetite for foods that taste different is unchanged. Brain imaging techniques show that when someone eats one food until they are satisfied, nerve and brain responses to that food decrease, although responses to other foods do not. Known as �sensory-specific satiety,� this phenomenon occurs in both normal and overweight people, and in response to both low- and high-calorie foods.

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Researchers say this is why people eat more as the variety of foods in a meal expands. When several different types of sandwiches or pizza are offered, people eat more than when just a single choice is available. People eat more ice cream when a variety of flavors are offered than when there is just one flavor, even if it is a favorite. The greater the variety of the foods' color, texture and flavor, the greater the increase in eating associated with that variety.

If greater variety of foods is linked with eating more, you might expect that diets with more variety would be linked with overweight. One study suggests that when people ate a greater variety of foods high in calories, such as snack foods, bakery goods and entr�es, they increased their calorie intake and body weight. However, when others in the study ate a greater variety of low-calorie vegetables, they ate a larger amount of vegetables, but gained less weight.

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Research in this field suggests that restricting the variety of flavors (orange, tomato, lemon, etc.) in a meal or a day's eating addresses just one component of sensory-specific satiety. Variety in texture, color and the taste differences in unflavored foods themselves (such as a plain piece of bread or plain pasta without sauce) may also influence pleasure and how much is eaten.

Studies show that weight control is often more successful when we eat fewer foods high in calories (such as fatty meats) and a greater proportion of our food is low in calories (such as vegetables). Sensory-specific satiety could make it easier to limit high-calorie foods and eat more low-calorie vegetables. We could create a meal that includes vegetables in a variety of different-flavored dishes - salad, soup and a stir-fry - as well as some fruit. Or, to limit time spent preparing meals, we might vary our choices of vegetables and fruits from day to day.

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Overeating can be caused by a large number of factors besides flavor, such as portion size. It may be a tricky balance to make food flavorful enough that we don't give up on healthy eating but, at the same time, not fill our plates with so much variety that we eat more than we need.