If you're struggling to lose weight, then be careful who you eat with. Scientists say we tend to consume a similar amount as our dining companions, and at the same pace.
The findings apply most directly to women, who are more concerned with social norms surrounding eating, say Dutch researchers.
They filmed 70 pairs of average-weight young women - a participant and an actor - sitting down for a meal together. Each was served the same dinner and told to eat as much or as little as they liked.
They found the participants immediately began copying the other diner in the number and timing of their mouthfuls - taking a bite within five seconds of the other person. They were three times more likely to do this at the beginning of the meeting, a sign they were trying to build on the relationship.
Lead author Roel Hermans of Radboud University in the Netherlands said the findings built on research showing women use other people as a model for "appropriate" eating. It is unclear whether this was a conscious move not to appear to be overindulging or something they do without realising.