It may be "just lunch" but a meal with an ex is dangerous territory for relationships, a study has shown.
A restaurant rendezvous is more likely to spark feelings of jealousy in a current partner than non-food related activities, US experts found.
Scientists say the findings underlie the fact that sharing food is more important than mere nutrition.
Beware having a meal with your ex, say experts
Students were asked to imagine how jealous they would be if their boy or girlfriend engaged with a former romantic partner in different circumstances.
They also had to imagine how their best same-sex friend would feel in the same situations.
Participants had to rate jealousy feelings on a scale of one to five, ranging from "not at all jealous" to "very jealous".
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The scenarios involved email messaging, speaking on the phone, meeting for coffee, or having lunch or dinner together.
Sharing meals prompted the strongest jealous response, and emails the least.
A morning coffee was seen as less innocent than a phone conversation, but not as serious as lunch.
In their paper, published in the online journal Public Library of Science ONE, the scientists refer to a dating service called "It's Just Lunch".
They wrote: "Our studies suggest that the professional matchmaking company 'Its Just Lunch' perhaps unknowingly benefits from implicit beliefs about eating together that helps them to connect people. But moreover, our findings also suggest that a more accurate and innocuous saying might be 'Its Just Coffee', since people seem to view drinking coffee during the day as relatively more platonic."
Study leader Dr Kevin Kniffin, from Cornell University, New York, said: "By applying a functional view of jealousy, our studies yield the inference that people think meals can be more than just meals."