Diners eating in the company of larger people have a tendency to eat more.

That's the basic finding of a new Cornell University study that found the body type of the people you are eating with or those around may influence how much you eat.

For the study, published in the journal Appetite, Cornell University Food and Brand Lab researchers gathered 82 undergraduate students and asked them to eat lunch. They set up a buffet that included spaghetti and salad. Researchers had an actress perform in four different scenarios to test how much food people took from the buffet.

  1. The actress wore a fat suit and served herself mostly salad
  2. The actress wore a fat suit and served herself mostly pasta
  3. The actress didn't wear the fat suit and served herself mostly salad
  4. The actress didn't wear the fat suit and served herself mostly pasta

Students served themselves more food, especially the less healthy pasta, when the actress was wearing the fat suit – regardless of what she ate. When the actress was wearing the fat suit, students served themselves 31 per cent more pasta. When she wore the fat suit and served herself mostly salad, students ate 43 per cent less salad. The study suggests that people are more likely to abandon their health goals when eating near an overweight person.

"This finding emphasizes the importance of pre-committing to meal choices before entering a restaurant," said Mitsuru Shimizu, lead author and psychology professor at Southern Illinois University, in a statement. "If you go into a 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."

The authors suggest the results may be because people are less in tune with their health goals when they are around overweight individuals.

"If you are going to a buffet, pre-commit to selecting modest portions of health foods with that goal in mind, those around you will have less of a negative influence over what you eat," said fellow author and director of Cornell's Food and Brand Lab Brian Wansink in a statement.

Katie Johnson of Mayo Medical School also co-authored the study.

Researchers said the point of the study isn't to fat-shame or assign blame for overeating, but rather to help people understand how environment influences eating habits.