The more you have on your plate, the more you overeat, according to a study in the October issue of the Journal of Nutrition.

Cornell University researchers found when served larger portions from one week to the next, young adults overate by almost 40 percent. Eating larger portions over time could account for the growth of the American girth over the past 20 years, the researchers noted.

"Since we know that restaurants are serving larger and larger food portions, we think that larger portions could be a major factor responsible for the increase in overweight and obesity that is so evident today," said lead researcher David Levitsky, professor of nutritional sciences and of psychology at Cornell.

Levitsky and Trisha Youn, now at the New York University School of Medicine, asked 13 student volunteers to eat a buffet lunch three times a week for two weeks. Some were served portions of the same weight as the previous week, while others were served portions weighing 125 percent or 150 percent more.

Volunteers served 150 percent larger portions from the buffet than the previous week ate an average of 39 percent more food in weight during the week than they did the previous week, an average of 273 more calories per person.

"From a public health perspective, the results of this study are extremely encouraging," Levitsky concluded. "If it's correct that the increase in portion size is a major cause of the epidemic of obesity, then it should be possible to stop and possibly reverse this trend toward increased body weight by taking control of size of portions served to the American people."

Other sources: Journal of Nutrition