Research shows different foods and nutrients affect how full and satisfied people feel. For example, a number of studies indicate that calories-for-calorie, protein makes a person feel more full than carbohydrates or fats. This suggests that eating adequate lean protein can help control hunger and food intake. Additionally, dietary fiber has been shown to affect the feeling of being full and food intake.

Research shows that eating an additional 14 grams of fiber per day is associated with a 10 percent decrease in calorie intake and a loss of body weight of a four pounds in four months. Eating more high-fiber foods such as fruits, vegetables and whole grains is a nutritionally sound way to not feel as hungry when reducing calorie intake. (Note: athletes wishing to increase fiber should do so gradually to avoid stomach upset, gas and diarrhea.)

Energy Density

In addition to nutrients such as protein and fiber, the energy content of food, gram for gram, also affects how full it makes a person feel. The term for this is energy density, which is simply the amount of calories in a gram of food.

The relationship between the weight of food and its calories content is largely affected by the amount of water in the food. Water adds weight but not calories, so the higher the water content the lower the energy density.

Studies consistently show that over the course of a day or two, a person eats about the same weight of food. On average, the weight of food eaten is more constant than an individuals daily calorie intake. Thus, if a person eats the same amount (i.e. weight ) of food, but lowers the calories in each portion, he/she will consume fewer calories. Studies also indicate that the calories won't be missed, the individual will feel just as full.

Tips on Lowering a Diets Energy Density

Increase the intake of water-rich fruits, vegetables, and soups

• Add fruit to breakfast cereal

• Choose fresh fruit for snacks

• Increase the amount of vegetables in pizza, stir-fry, and pasta dishes

• Include a tossed green salad with lunch and dinner

• Choose broth-based soups before meals or as a meal

Increase consumption of dietary fiber

• Increase fiber intake by eating more high-fiber cereal, whole grains, legumes, vegetables and fruits.

• Limit intake of dry foods

• Limit consumption of dry foods such as pretzels and crackers, as they are dense in calories and are easy to overeat

Choose beverages wisely

• Drink water, low-calorie or calorie-free beverages such as fruit juice diluted with seltzer, diet soft drinks, etc.

• For snacks, "liquid foods" such as vegetable cocktails and drinks containing protein, such as those based on milk, are good choices to increase the feeling of fullness.

Practical advice on how to apply the science of satiety (or the feeling of fullness) and lower energy density of a diet is in several consumer books recently published. Athletes wishing to reduce calorie intake may benefit from this new science.