People eat more when presented with a variety of foods, according to Cornell University research. In the study, 20 college students were allowed to eat their fill from a buffet that consisted of either three items (chicken, a vegetable, and a carbohydrate like rice), or two items (either chicken and a vegetable or a vegetable and a carbohydrate.) The researchers found that the students ate more in terms of the amount of food and calories of the three-item buffet, less of the two-item, low-carbohydrate meal, and the least of the vegetarian two-item meal. "If you pulled away the protein, you increase the amount you eat of the other foods, but not enough to make up for the caloric deficit," says study author David Levitsky. "The same thing occurs if you pull the starches away." In a follow-up study, the students were either given a one-dish meal of a stir-fry or a pasta dish that included a variety of vegetables or a meal with each of the vegetables and the starches served separately. Again, participants ate significantly more of the foods when they were served separately than when they were served in a one-dish meal. The experiment suggests that both low-carbohydrate and vegetarian diets may be successful because they restrict the variety of foods people eat. The research also points to the environment as a major contributor to the obesity epidemic. "One idea is that we have evolved from creatures for whom the sight of food is the stimulus to eat, because they couldn't store the food." Levitsky says. "I think that's what these findings are representing, this mechanism that tells us 'the more food is available, the more you have to eat it, because you never know when it's not going to be there.'"