So your ex contacts you on Facebook and suggests catching up over a meal. You may think it's not a big deal, but a recent academic study at the Cornell Food and Brand Lab found that even casual dining with an old flame is a minefield you'd best not traverse. While you regard it as a harmless get-together, chances are your current honey won't see the encounter that way. In other words, he or she is going to be upset and you could end up sleeping on the couch.

“You might want to make it coffee, not lunch,” lab director Dr. Brian Wansink, Ph.D., author of Mindless Eating: Why We Eat More Than We Should, told Squid Ink. Either that, or bring along a third wheel, to neutralize the romantic vibe that can be served up during a meal.

Asked where the idea for this study came from, Wansink said it was jump-started after he proposed that two colleagues have a working dinner in order to make progress on a lab project. The male and female co-workers (married to other people) balked at the idea of going out to eat together, with the man proclaiming that his wife wouldn't feel comfortable if he had dinner with another woman.

Wansink, a well-regarded researcher in the field of food psychology, was intrigued by this reaction. What was it about sharing an innocent meal that could trigger such worries?

He and his co-researcher, Cornell behaviorist Dr. Kevin Kniffin, Ph.D., asked 79 college students to rate their level of jealousy over interactions between their current boyfriend or girlfriend with his or her ex. Jealousy was rated on a scale of 1 (for not at all jealous) to 5 (very jealous.)

Because the researchers suspected that most people — especially men — don't like to admit to feeling jealous, they also conducted a second study, asking participants to imagine how their “best friend” would respond to the same scenarios. As expected, that emotional fictional friend unleashed way more of the green-eyed monster. Not expected, men and women appeared to have equal levels of jealousy, which ballooned as more calories were consumed later in the day.

Participants were given six situations, each introduced with the phrase “Recently, your (romantic partner) was contacted by his/her ex-(romantic partner) and she/he spent approximately one hour” in one of the following activities: corresponding by email; talking on the phone; meeting for a late-morning cup of coffee; meeting for lunch; meeting for a late-afternoon cup of coffee; meeting for dinner.

Having morning coffee elicited about the same level of jealousy as a phone call. But late afternoon coffee caused more jealousy than a cup of joe early in the day. And emotions increased dramatically at lunch and skyrocketed even more at dinner. The researchers concluded that when it comes to interacting with an ex, there's no such thing as “just” a meal. Or, to put it in the study's science speak: “… It becomes clear that the practice of eating together might have functional significance beyond the concurrent consumption of calories.”

Published in the journal Public Library of Science, the study concluded that relationships can be threatened by “extra-pair commensality.” (So that's what they're calling it these days. Actually, it just means eating with someone who is not your significant other.)

All this brings to mind that classic Seinfeld episode when George eats a pastrami sandwich while having sex. Pretty sure that's not a good thing to do with your ex, either.

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