Are habits contagious?

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Are habits contagious?

Contagious Habits: How Obesity Spreads
By Jonah Lehrer April 19, 2011 | 2:06 pm | Categories: Frontal Cortex, Science Blogs
A few years ago, Nicholas Christakis and James Fowler made a striking discovery about obesity: it spreads from person to person, much like a contagious virus. They were able to demonstrate this by mining the data sets of the Framingham Heart Study (FHS), a longitudinal survey that has revealed many of the risk factors underlying cardiovascular disease. Because the FHS noted each participant’s close friends, colleagues, and family members, Christakis and Fowler were able to recreate the social network of the town, to see how everyone was connected to everyone else.

And this is when they made their remarkable discovery about weight gain. According to the data, if one person became obese, the likelihood that his friend would follow suit increased by 57 percent. (This means that the network is far more predictive of obesity than the presence of genes associated with the condition.) If a sibling became obese, the chance that another sibling would become obese increased by 40%, while an obese spouse increased the likelihood that the other spouse would become obese increased by 37%.

The Christakis/Fowler work is an important reminder that Donne was right: No man is an island/entire of itself. Instead, we are all plugged into a vast network of social contacts and cultural norms. While we think ourselves as autonomous individuals, that autonomy is severely constrained by those around us.

But this longitudinal data – it’s a bird’s eye view of human life – still begs the question: How do other people influence us? Why does an obese friend make us so much more likely to gain weight? Why do the habits of others influence our own habits?

A brand new paper by researchers at the University of Colorado at Boulder helps answer these important questions. The scientists begin their paper with a compelling hypothetical:

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?
When asked this question, a majority of people insist that the picture of Lucy would reduce their consumption of cookies. (31 percent believed that Lucy 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.

In one of their experiments, researchers asked random strangers walking through a lobby at the University if they would take a quick survey. The surveys had photos of an overweight person, a person of normal weight or a lamp. After completing the survey, the researchers asked the subjects to help themselves from a bowl of candy. Those who were exposed to the picture of the overweight individual took, on average, 3o percent more candies than those exposed to the control pictures.

In a second study, subjects were invited to do a cookie taste test. Those who were first exposed to pictures of overweight individuals ate twice as many cookies as those were exposed to images of trees, fishbowls and non-overweight subjects. This effect held when participants said they had a goal to maintain a healthy weight. As the researchers write, “Exposure to a negative stereotype [seeing someone who is overweight] can lead to stereotype conducive behavior.” Even when we are determined to maintain our diet, we are still subtly undermined by the choices and habits of everyone else.

This research builds on a 2010 paper by Northwestern psychologists that demonstrated that people anchored their own portion sizes to the portions around them. If we’re surrounded by people eating a supersized Big Mac meal, then we’re much more likely to do the same.

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.

Are those who we choose to surround ourselves with shaping our own bodies? Do you agree or disagree with this theory, and why?

Would you be willing to change your group of friends if it ultimately meant changing your life/health for the better?

b525's picture
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Wow! I could definitely see how this theory could be true. You see it when they talk about cultural stereotypes. I'm a big fan of the show Biggest Loser and they've had several contestants who are Tongan. They talk a lot about how that culture practically revolves around food and it's almost considered a bad thing to be thin. In my own experience, I have quite a few friends who have recently gotten motivated to get fit and are working out and often doing FB posts about being at the gym or heading out to run or whatever. It's a kick in the behind for me, especially when it's a person who has all my same excuses for not exercising on a given day. So, if peer habits in other areas, such as exercising, can influence people around them, I can certainly see how eating could do the same thing.

I would not be willing to change my friendships over it, but it might be a good thing to keep in mind, to be really vigilant about my own food choices.

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To me it makes total sense.

I would not be willing to lose friendships over it, but I would absolutely take the concept into consideration when making new friends. I think that seeking out people who you would like to emulate, rather than those who make you feel "comfortable" is good for all of us ~ whether that is about weight, religion, education, athleticism etc.

Like attracts like. And to me, this suggests that like also can *create* or at least influence like.

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I agree with you. It's easy for friends and family members to fall into the same habits - good or bad when it comes to food. The studies were interesting.

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Maybe I'm just used to being different, but I don't get it. Just doesn't connect with me. My eating habits -- when they were very unhealthy, or now as I am on a kick to get fit and healthy -- have nothing to do with the habits of people in my life. Most of my friends are pretty healthy and fit, a bunch of them aren't, and that has never really affected me one way or the other in terms of action. (Certainly I can go out with my skinny friends and feel crappy about myself, but I never changed what I was eating because of it.)

I have friends who aren't all that like-minded too....friends I adore but don't want to emulate, too. There is always some quality I admire but it often balances out.

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I can see how this is true. I have a friend I've know for a bit over a year, and her healthy lifestyle has encouraged me to get in shape as well.

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Of course... Especially in familial relationships Wink

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I think it depends on how social eating (and body image?) are for each person if you are simply talking about friendships. For a spouse, I would say it definitely has a big effect since it's a larger effort to eat completely separate meals or eat spinach while your spouse has a bowl of ice cream.

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It makes sense to me. It might not change your behavior permanently for at least for the time spent with them it makes a difference and if you spend a lot of time with a person, I can see it making an impact on your health. If all your friends like to sit around watching movies and eating chips, you probably aren't going to suggest going for a hike. You're probably going to sit down and eat with them. The opposite holds true as well. Any time spent with my ultra fit, spinach eating friends will be "healthy time".

As you move toward either end of the health spectrum, you probably spend less time with people on the other side.

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Makes sense to me. I am not overweight by any means, but I am not as in shape as my close group of friends that have been participating in triathlons for the last few years while I was pregnant and then dealing with 4 kids. I like working out, but working out and getting the opportunity to spend time with them has been a huge motivation to get in better shape.