Researchers say portion size plays an even bigger role if the contents are fresh. While the subjects given stale popcorn consumed 37 percent more from big tubs, those with big tubs of fresh popcorn ate 45 percent more.
"We're finding that portion size can influence intake as much as taste," said Brian Wansink, a professor of marketing and of applied economics at Cornell. "Large packages and containers can lead to overeating foods we do not even find appealing."
Wansink said larger portions appear to reset thinking about what is a normal amount to eat. He has done earlier studies that show people tend to underestimate the calories they are consuming -- and to underestimate them even more when the food does not taste good.