If you're looking to lose weight, here's a simple tip: don't dine with the skinny dude who stuffs his face. According to a study that will appear in the April 2010 issue of the Journal of Consumer Research, both the size and the consumption habits of our eating companions can influence our food intake. And contrary to existing research that says you should steer clear of eating with heavier people who order large portions, it's the beanpoles with the big appetites you really need to avoid. "They're big trouble," says Gavan Fitzsimons, a marketing professor at Duke's Fuqua School of Business and one of the study's co-authors.

To test the effect of social influence on eating habits, researchers conducted two experiments. In the first, 95 undergraduate women were individually invited to a lab ostensibly to participate in a study about movie viewership. Before the film began, each woman was asked to help herself to a snack of either M&M's or granola. Another "participant," who was actually an actor hired by the research team, grabbed her food first, in full view of the subjects at the snack line. In her natural state, the phony participant weighed 105 lb. and wore a size 0. But in about half the cases, she wore a prosthetic designed by an Academy Award–winning costume studio. The fat suit increased her weight to 180 lb. and puffed her clothes to a size 16.

Each of these tests illustrates the psychological trait known as anchoring. Humans tend to latch on to one specific piece of information when making decisions, in this case the habits of the actor. The social environment is extremely influential. If this fellow study subject is going to take an above-average number of M&M's, so will I. Call it the "I'll have what she's having" effect.

Interesting... I can see why though... people don't realize that everyone is different. They think that what works for one person will work for them and if they see a thin person eating, they think it's okay for them to do it too. Some people have way overactive metabolisms that can eat whatever they want... others spend hours at the gym to compensate for their diets. People don't see this! All they see is that the person is having extra m&ms so why not me too.

This is true... I feel like I eat more when I am around people that are eating more and I feel like I eat less when I am around people that eat less!

I always feel it is okay to eat more than my thin friends... but feel bad when I eat more than my heavier friends. I wonder why that is?!? It shouldn't matter, but it does.

Really? I don't think I feel bad when I eat more than my heavier friends... I guess maybe I just figure I workout more and earn it?

That's not true... You'd feel bad if you ate more than I did... don't lie

One way or another, we have to control ourselves when it comes to eating.