You aren't just what you eat, you are also likely to be who you eat with. Your dining companions' weight can affect your food choices.

In a study that may remind you of the Hollywood movie, Shallow Hal, researchers put an actress in the same sort of “fat suit” Gwyneth Paltrow wore in that film. The results clearly suggest that people indulge more if they are in the presence of an overweight person.

It didn’t matter whether the actress served herself a small or large portion of pasta while in the fat suit. The students still took more and ate more pasta in the presence of the overweight version of the actress than the normal weight version.

Undergraduate students in groups of 10 to 12 were asked to serve themselves a meal of pasta with meat sauce and a salad.

At each group’s meal, the first person in line was a professional actress whose job was to make herself conspicuous by intentionally dropping a fork and requesting a new one or asking for instructions out loud such as, “Do I need to use separate plates for pasta and salad?”

She was also seated near the serving station to increase her visibility.

During half of the meals, the actress wore a fat suit that made her appear to be 50 pounds heavier than her actual weight. Sometimes she served herself large portions of pasta and a small salad, and other times she took a lot of salad and a smaller portion of pasta.

At the other meals, she didn’t wear the fat suit, but still made sure the students noticed her.

The researchers — Mitsuru Shimizu, of Southern Illinois University-Edwardsville, and his colleagues and Katie Hancock and Brian Wansink of Cornell University — measured the food served and eaten by the student participants. They found that the weight of the actress-confederate influenced students' selections.

When she looked 50 pounds heavier, students took larger portions of and ate more pasta, a food previous research had shown college students viewed as a high calorie, unhealthy choice.

It didn’t matter whether the actress served herself a small or large portion of pasta while in the fat suit. The students still took more and ate more pasta in the presence of the overweight version of the actress than the normal weight version.

Even more curious is the fact that the students consumed less salad when the actress wore the fat suit and served herself healthy portions compared to when she appeared overweight and served herself a large portion of pasta.

The researchers believe that people are less mindful of their health goals when they are eating with overweight people. Maybe in this situation we experience a subliminal form of peer pressure, or our good judgment takes a break since we feel comparatively thin.

Either way, you may want to watch yourself when eating with overweight friends, family, or colleagues.

The study is published in Appetite.