When dining out with friends that are on the huskier side, common sense dictates that their size might caution you to make healthier choices when selecting your own meals. That’s not the case, according to a study conducted by researchers from Cornell and Southern Illinois University: They found that if anything, larger dining companions inspire us to eat more ourselves.

“This finding emphasizes the importance of pre-committing to meal choices before entering the restaurant,” says lead author Mitsuru Shimizu, Assistant Professor of Psychology at Southern Illinois University, Edwardsville. “If you go into the restaurant knowing what you will order you’re less likely to be negatively influenced by all of the things that nudge you to eat more.”

To conduct the study, the researchers enlisted 82 undergraduates. one actress, and a “fat suit” that added 50 visual lbs to the actress’ otherwise average frame. Participants were invited to a pasta and salad luncheon, and placed in one of four scenarios with the actress – she served herself either healthily or unhealthily (more salad versus more pasta), and both with and without the fat suit. Researchers then observed how the students fed themselves.

When the actress served herself more salad while wearing the prosthesis, students actually served themselves 43.5% less salad. Regardless of how she served herself, the presence of the fat suit led students to serve themselves 31.6% more pasta in general.

As to why this happens, the researchers have no definitive answer but suggest that eating in the presence of overweight people might skew the perspective of one’s own health goals. Still they say it’s an effect that shouldn’t be difficult to combat.

“Look up the menu beforehand and select a meal that suits your dietary goals. Or, if you’re going to a buffet, pre-commit to selecting modest portions of healthy foods and with that goal in mind, those around you will have less of a negative influence over what you eat,” said Brian Wansink, PhD director of Cornell University’s Food and Brand Lab.