Your dinner partner can have a big influence on your eating habits, especially when it comes to how much you consume, according to a meta analysis from the University of New South Wales in the UK.
It's a psychological effect called social modeling, according to the study, that leads you to consume less than you would otherwise if your cohort is a light eater.
The phenomenon occurs because in social situations it's not clear how much is too much to consume, says lead author Lenny Vartanian, an associate professor at UNSW School of Psychology.
"Internal signals like hunger and feeling full can often be unreliable guides," he says. "In these situations people can look to the example of others to decide how much food they should consume."
Vartanian and his colleagues analyzed 38 studies to arrive at their conclusion and their paper was published in the journal Social Influence.
They found that the phenomenon of social modeling occurs regardless of an individual's body weight and that women are more likely to succumb to it than men.
This could occur because women exhibit more concern about how others perceive them when they are eating, say the researchers.
"Or the explanation could be more mundane, that undergraduate males participating in the research are over-enthusiastic about an offer of free food," says Vartanian.
The modeling effect occurs even in the absence of the companion, according to the study, if the person dining reads a written synopsis of how much his would-be-dinner-partner noshed.
The phenomenon is stronger in older children than in the younger set, which suggests that taking cues from external sources is a learned behavior.
"The research shows that social factors are a powerful influence on consumption," says Vartanian. "If the social model eats a large amount, people have the freedom to eat their normal intake, or even more if they want."
Portion size has come under fire in the battle against obesity, and Vartanian says social modeling merits more attention because it's a powerful influence on how much people consume.