Going with Your Gut: Subtle Cues Spread Obesity

Obesity is, apparently, transmissible. Studies already found evidence that it spreads through communities and social networks. If you have a friend who becomes obese in a time period, you’re 57% more likely to follow suit. But it’s not just shared regional foods or common experiences. Merely interacting with overweight people impacts us — and not the way most people expect when asked.

A new study found that simply seeing pictures of overweight people motivates us to eat more. Jonah Lehrer describes the situation:

A majority of people insist that the picture of [an overweight person] would reduce their consumption of cookies. (31 percent believed that [seeing it] would inspire them to abstain entirely from the sweet treat.) This is how we like to think ourselves: independent minded creatures, able to learn from the unflattering photographs of others.

Alas, our responsible self-image is entirely divorced from reality. The Colorado researchers demonstrated that, in several situations, the exact opposite occurred: When people were exposed to pictures of someone who was overweight, they ended up consuming far more calories.

It’s a neat study. The researchers asked people to take a quick survey which had a random picture of an overweight person, a person of normal weight, or a lamp. Afterward, the subjects were invited to take candy from a bowl. The ones whose surveys had the picture of the overweight person took 30% more. In a similar study, the subjects were asked to do a cookie taste test (what an offer!). Those first exposed to pictures of overweight people ate twice as many cookies.

The first takeaway lesson is that if you’re asked to participate in a psychology study, there’s almost always a trick – they’re probably testing something completely different than what they claim. (On a side note, if there’s one other “subject” with you; don’t trust him. He’s almost certainly working for the researchers. Cynical and paranoid enough for you? …*cough* But back to the study at hand.)

Taken together, this research begins to explain how obesity moves through a social network. It turns out that the habits and hungers of others shape our own, that we unconsciously regress to the dietary norms around us. Because we’re not particularly good at noticing when we’re sated and full – the stomach is a crude sensory organ – we rely on all sorts of external cues to tell us how much to eat. Many of these cues from other people, which is why our eating habits are so contagious.

It’s not shocking when we look at it like that: we look to others for signs of how to act. A picture of a stranger influences us – and even if the subject explicitly stated a goal to maintain healthy weight.

The point that our stomachs are crude sensory organs hit home for me. Those “external cues” influence our perception even about something as intimate as the amount of food we want to eat! “Going with your gut” to make the decision is an easy strategy but doesn’t lead to great results. If we want more control over our weight, a more objective and deliberate strategy based on measures like calories, glycemic index, and metabolic rates would probably work better.