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A few years ago around the time I was working on my dissertation, a study came out suggesting that obesity was contagious (Christakis and Fowler 2007). In short, according to the study, if your friends were obese, your likelihood of becoming obese increased substantially. I was also aware of several studies that showed that we eat similar to those around us: If everyone at the table orders the steak, your portion choice will be larger than if you first overhear others choose a garden salad. Similarly, if no one orders dessert, do you really want to be "that guy (or gal)" who does? Likely not.
So if we put these two findings together—the most dangerous people to eat with are obese people who eat a lot. This really didn't sit well with me: Seeing someone who is obese overindulge does nothing for me wanting to order more food; if anything, it would turn me off.
To answer this question, I ran a series of experiments published in the Journal of Consumer Research (McFerran, Dahl, Fitzsimons, and Morales 2010). I varied what people saw others choose as well as this other's body type (using an obesity prosthesis or colloquially, a "fat suit"). What I found was that people used the other's choice as a guide that informed their own choice of how much to put on their plate. She eats more, so did participants. That part wasn't terribly surprising. The unique finding was that extent to which people's anchored on the other's choice depended on whether the other was thin or obese (because she was in the fat suit). When she took a large portion, participants took and ate more when she was thin than when she was obese. The opposite occurred when she took a small portion: Participants took and ate less when she was thin than when she was obese.
So according to this work, the most dangerous people to eat with are not the obese, but rather thin people who eat a lot of food. You see that thin girl take a large ice cream, you think, "She can eat that and stay thin, I can too!" Of course, this influence depends on you overhearing others' choices. Be the first to order and you set the bar for others.
But a natural question remains: What if you just see the other person's body type, but don't observe this person's choice? A new paper, also in the Journal of Consumer Research, by University of Colorado-Boulder Marketing professor Margaret Campbell and PhD student Gina Mohr answers this question directly. Before you guess what happens, let me take a hypothetical situation from her paper:
"Consider the following: Your friend Lucy, who is about 25 pounds overweight, e-mails you pictures from her recent vacation. After you look at Lucy's pictures, the office secretary comes by with a plate of cookies. Will exposure to someone who is overweight influence how many cookies you eat?"
What did you guess? If you are like participants in their study, most insist that seeing Lucy will reduce their own consumption.
Interestingly, the opposite occurred. The authors presented participants with images of normal weight people, overweight individuals, or control images like trees or lamps. They found across several studies that people exposed to pictures of overweight others consumed the most calories. They argue that even subtle contextual factors can influence our food choices in ways we don't expect.
I've got to run now...meeting some friends for dinner.
