“If a heavy-set colleague eats a lot, you are likely to adjust your behavior and eat less. But a thin friend who eats a lot may lead you to eat more than you normally would,” the study authors wrote.
“We decided to investigate how someone’s size and food choices could influence how much the people around them eat,” write researchers Brent McFerran, Darren W. Dahl (University of British Columbia-UBC), Gavan J. Fitzsimons (Duke University) and Andrea C. Morales (Arizona State University).
They recruited 210 college students to participate in a study that was ostensibly about movie watching. Participants were told they would be paired with another student for the study.
The other student was actually a member of the research team whose natural build was thin. But at times this same researcher donned an “obesity prosthesis,” which made her appear a size 16 and 180 pounds.
All of the students were offered snacks while viewing the film clips. The undercover researcher was served first, and helped herself to either a large or small serving before the student participant was offered the same bowl of food.
In all cases, the amount of food the students accepted was influenced by the portion size chosen by the undercover researcher, regardless of her size.
Participants tended to mimic the thin companion’s portion sizes. But when they presumed the researcher to be obese, the participants adjusted the amount they ate.
“This indicates that people are influenced, even without being aware of it, by other people’s portion choices,” the authors wrote.
These findings were published in the Journal of Consumer Research.