Big Portions May Prompt Overeating

Nov. 18, 2005 -- Portion size may matter nearly as much as taste when it comes to overeating, according to a new study.

Researchers found people ate 34% more stale popcorn if it was served in a big bucket than those given the same stale popcorn in medium-sized containers.

But the bingeing was even worse when people were given fresh, tasty popcorn in an oversized bucket. People ate 45% more of the fresh popcorn than those given fresh popcorn in medium-sized containers.

"We're finding that portion size can influence intake as much as taste," says researcher Brian Wansink, PhD, professor of marketing and economics at Cornell University, in a news release. "Large packages and containers can lead to overeating foods we do not even find appealing."

But researchers say the good news is that the effect of portion size on overeating may also apply to healthier fare, like fruits and vegetables.

"While a small bowl of raw carrots might make for a good afternoon snack, a large bowl might be even better," says Wansink.

Research at the Movies

In the study, published in the Journal of Nutrition, Education, and Behavior, researchers gave 158 moviegoers either medium (4.2-ounce) or large (8.4-ounce) tubs of popcorn that was either fresh or 14 days old.

After the movie, researchers measured how much popcorn was left in the containers and asked the participants to describe the popcorn they ate.

The 14-day-old popcorn was described as "stale" and "terrible." Nonetheless, those given the big tub of stale popcorn ate a third more of it than those given the smaller container.

Researchers asked the moviegoers if they thought they ate more because of the size of the container; 77% said they would have eaten the same amount if they were given a medium bucket.

But researchers found the amount of popcorn eaten varied dramatically despite the fact that moviegoers were randomly assigned to receive either the large or medium bucket.

"This means that the moviegoers were unaware that the exceptional amount they ate was due to the size of the container," says Wansink.

Researchers say larger portions may implicitly suggest what a "normal" or "appropriate" amount to eat is and prompt people to eat more than the recommended serving size of foods.