The Importance of Friendship

When Harvard University social scientist Nicholas Christakis and University of California, San Diego professor James Fowler published their groundbreaking study about the contagion of obesity in 2007, the duo was particularly amused by the difference between how American and European headline writers framed the findings. The paper, published in The New England Journal of Medicine to much fanfare, revealed that weight gain could spread like a cold or flu, “infecting” friends and family out to three degrees of separation. In other words, if your friend’s friend’s friend gains weight, it increases your risk of getting fat—and the closer the degree of separation between you and the person beefing up, the more likely you’ll pack on some pounds as well. “American headline writers all said, ‘Are you gaining weight? Blame your fat friends,’ ” Christakis says. “The Europeans asked, ‘If your friends are gaining weight, are you to blame?’"
The American viewpoint tends toward individualism and self-focus. We are, after all, a nation in which calling a politician a socialist is akin to calling him a child molester. But over the past few years, with the publication of their research and, last fall, of their mind-blowing book, Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives, Christakis and Fowler have been methodically turning American narcissism on its head, showing that everything from whether you vote, marry, divorce, have kids, smoke, gain weight, donate money, become depressed or happy or violent or lonely is consciously—and subconsciously—influenced by your social circle. “The arguments in our book give a whack to free will,” Christakis says. And, the authors write, “Recognition of this loss of self-direction can be shocking.”
However, in this loss there’s a gain: We may be under the sway of others, but they are also under our sway. We have real power to change the lives of thousands of people, considering that our capacity for persuasion generally extends to three degrees, and that psychologist Stanley Milgram posited in the 1960s that the whole world is, on average, separated by only six degrees. It’s pretty heady stuff: When you smile at a neighbor or donate money to UNICEF, for example, your action travels like a wave, washing over thousands of other people, nudging them toward happiness and charity.
Based on Christakis and Fowler’s research, here are some ideas for magnifying and maximizing your ability to pay it forward:
1. Have a Party
People who are “central” to their social networks not only themselves have a lot of friends, but their friends also have more friends. And the more central your position in your social network, the better a vector you are for ideas, viruses, and habits. So the center is a bad place to be if swine flu is going around, but a great place to be if happiness or money is in the air. Christakis and Fowler call it the “centrality premium.” Assuming your goal is to pass around the good stuff rather than syphilis or suicidal ideation, your best bet is to maintain your current relationships while making new friends as well, allowing your influence to stretch as far as possible. (Also, bonus mitzvah: You could even make a match. In a study of American married couples, more than two thirds were introduced by a friend or family member.)
2. Lose Weight
Since Christakis and Fowler published their study showing that obesity was socially transmissible among members of the famous Framingham Heart Study (it wasn’t just that birds of a feather flock together: People were actually making one another gain—and, sometimes, lose—weight), the finding has been confirmed in multiple other populations. So how do people infect each other with fat? One way is imitation. Brain scans show that when you watch someone else eat or run, your brain activity is the same as if you were eating or running yourself, priming you to do the same things. And people in experiments seated next to robust eaters will eat more than those seated next to light eaters. Social norms also play a role: If your friend gains weight, you might become less motivated to go to the gym because your friend’s example showed you that weight gain isn’t the end of the world. She’s heavier but still the same person you know and love. And now that 66 percent of the American population is overweight or obese, that’s a pretty well-established social norm.
Happily, this effect could be turned on its head if people worked to establish an opposite social norm—weight loss can spread just as easily as weight gain if you seed your network with fat-fighting habits. In Christakis and Fowler’s book, they suggest starting a running club containing friends of friends so that you’re surrounding yourself and your closest contacts with exercisers (and remember, when people see you run, it makes their brains think about running too). You can also make healthier food choices and eat with greater restraint. If you take a pass on the fries and eat more vegetables, your pals are more likely to make the same choices. And then, once you reach a healthier weight, you might shift the norms in your group.
If you’re thinking that sounds like a lot of work and maybe it would just be easier to ditch friends who gain weight to prevent them from corrupting you, Christakis says he and Fowler actually looked into this as a diet method and found that it didn’t work. People who cut ties with a fat friend didn’t lose weight, possibly because the toll of losing a friend counteracted weight-loss efforts.