Dining with an overweight person may cause people to eat more unhealthy food, according to a study in the journal Appetite.

College students were more likely to serve themselves more pasta and less salad when a fellow diner was wearing an overweight prosthesis, or “fat suit,” in the study conducted at Cornell University in New York.

When eating with an overweight person, people not only ate “a larger amount of unhealthy food, but they ate a smaller amount of healthy food,” said Mitsuru Shimizu, assistant professor of psychology at Southern Illinois University Edwardsville, in an email.

Shimizu, who led the study, and his co-authors think the presence of the overweight person derailed the students’ intentions to eat “healthy,” although the researchers don’t say why a heavy dining companion would have that effect.

There are many unconscious influences on how much people eat, the study team points out in its report. For example, they note that simply eating with another person can cause diners to eat up to 44 percent more than when eating alone.

“While we often have good intentions before we go to a restaurant (I'm going to get the side salad instead of fries), when we arrive, a lot of cues can prime us to want to indulge. These include, the smells, what our companion eats, and now perhaps even the weight of our companion,” Brian Wansink told Reuters in an email.

Wansink, who also worked on the study, is the author of “Slim by Design: Mindless Eating Solutions for Everyday Life.”

The researchers selected 82 university students for the study. Half of the students served themselves food in the presence of a woman in a prosthesis, while the other half encountered the same woman with no body alterations.

Within each of these groups, the students were split again. Half saw the woman serve herself more salad and less pasta and the others saw her serve more pasta and less salad.

After watching the woman serve herself, the students made their own food selections while the researchers observed.

The results showed that students who observed the woman in the prosthesis served themselves 31 percent more pasta, regardless of how the woman served herself. The students also served themselves 43 percent less salad when the woman wore the prosthesis and served herself more salad.

Shimizu said the presence of the overweight eating companion “deactivated participants' goal to eat healthier (we generally have unconscious goal to eat healthy).”

“The study is generally well-conducted,” according to Brent McFerran of Simon Fraser University in Burnaby, British Columbia, who studies how the behavior of others influences consumer choices.

One limitation, the researchers acknowledge in their report, is the weight of the participants themselves. Only two out of the 82 students were obese, while the Centers for Disease Control and Prevention estimate that 34.9 percent of U.S. adults are obese.

This factor limits how broadly the results might apply, they said. They also hope to continue their research using a wider range of foods for participants to choose from.

The researchers note that the solution to the phenomenon seen in the study is not to avoid eating with overweight companions, but to combat the lowered focus on health goals with awareness.

Shimizu said that while the influence takes place unconsciously, simply knowing about this effect “should decrease the impact.”

Wansink’s advice is simple: “Commit to what and how much you want to eat before you get to the restaurant. Really commit to it.”

McFerran agreed and advises diners to “order or serve him/herself first.” The first person to order or take food, he said, “sets a social norm about what is a ‘good’ or ‘normal’ amount to take. Who wants to be the only person to order dessert? Not many people.”