On one day, they ate the meal in the standard fashion - all at once. On another day, all of the food was served together, but in four smaller packages; the point was to see if a different "visual cue" would change the teens' food consumption.
Under the third condition, the meal was served in four smaller portions, offered in 15-minute intervals. This change was designed to slow the rate of eating, which in theory could prevent gorging.
But in the end, Ebbeling's team found, the teens ate a similar number of calories no matter how the food was presented -- around 1,300 calories, on average, with each meal.
Ebbeling stressed that the way the meals were served was fundamentally different from portion control; each meal offered the same amount of food, just presented in different ways. So eliminating giant portion sizes remains a worthy goal.
"Portion control is really important," she told Reuters Health. "We know that people eat less when they're given a smaller portion."
But the study does suggest that changes in the nutritional quality of these foods, and not just their portion sizes, may be needed.