Researchers at Cornell University have found that consumers are often influenced by the labels describing portion size and it dictates how much quantity of food is 'normal' size and they adjust their consumption accordingly.
"People are willing to pay more for a portion that sounds larger, but they also are apt to eat more of an enormous portion if they believe it is 'regular' to do so," David R. Just, associate professor at Cornell's Dyson School of Applied Economics, said.
In their study, Just and Brian Wansink, professor of marketing at Cornell served study participants either one or two cups of spaghetti.
For some participants, the small and large portions were labeled "half-size" and "regular," respectively, giving the impression that the larger two-cup portion was the norm.
For other participants, the same portions were labeled "regular" and "double-size" - implying that the smaller one-cup portion was the norm.
"These varying concepts of 'regular' portions made all the difference in how much people would spend and subsequently eat," Just said.
"Participants ate much more when their portion was labeled 'regular' than when it was labeled 'double-size.' In fact, participants who thought their portion was 'double-size' left 10 times the food on their plate," he said.
Exploring how portion labels impact the willingness of patrons to pay, the researchers let participants bid on each portion.
When the portion was labeled "half-size," participants were willing to pay only half when the same portion was labeled "regular." The labels, rather than the visual appearance of each serving, acted as indicators.
"The huge impact of size labels suggests that both consumers and producers could benefit from standardization of food size-labeling," Wansink said.
The study is published online in the journal Health Economics.