We all have that thin friend who can eat and eat and somehow never gain a pound. As it turns out, dining in her company may be dangerous for your diet. According to a study published in the Journal of Consumer Research, watching a thin friend overindulge makes us feel we can do the same. But when we eat in the company of heavier friends who overeat, we’re likely to exercise more self-control. Researchers had 210 female college students watch a movie with a woman who sometimes appeared as her normal thin self and other times in a fat suit. The students ate more of the snacks offered when their thin companion took a large portion than when their obese companion took a similarly large portion. The study highlights how much social pressures affect our eating habits. The next time you make dinner plans with that skinny friend, don’t keep up with her excessive eating.