Similar friends may spread healthy behaviors
December 2nd, 2011
06:00 PM ET

Similar friends may spread healthy behaviors

Who you know influences how you behave, a growing body of research is showing.

Networks of people who know each other can spread the good (happiness) and the bad (obesity, STDs and loneliness).

But it's not just any social network that propagates behaviors and diseases. New research published in the journal Science suggests that having social network contacts of similar gender, weight and body-mass index could help people pick up on healthy behaviors.

The study did not conclude which of these factors is most important, but that will be the subject of follow-up work, says Damon Centola, study author who is a researcher at the Massachusetts Institute of Technology.  It also does not prove that the network caused behavior adoption, but puts forth questions for further study.

Researchers recruited 710 participants from online fitness programs. They were all randomly assigned to work with volunteers in social networking communities.  However, some participants were assigned to so-called "clustered communities," where they were connected to 6 heath buddies, who shared similar body mass index, gender and age.  Other trial participants were assigned to "non-clustered communities," which meant they were connected randomly with participants, with whom they didn't necessarily share any traits.

Each participant got a personalized "health dashboard" showing his or her own health behaviors and those adopted by health buddies.

The study set up the situation where participants had to decide whether to adopt (or agree to use) an online diet diary.  A notification from the dashboard would tell participants if their health buddies had adopted the behavior.

In each network, participants received a notification that a person in their network with above-average fitness, high exercise minutes and low BMI had chosen to use the diary. In reality, researchers sent out that notification to see how the behavior would spread.

Researchers found that three times more participants in clustered social networks adopted healthy behaviors from the diary than their counterparts in the unstructured networks did.

Relative to their study population sizes, a greater percentage of obese participants chose to adopt the diet diary in the clustered networks compared to non-obese volunteers. And not a single obese participant in the unstructured networks signed up for the diary. Generally speaking, the clustered networks greatly increased the likelihood of adopting the diary, especially among the less physically fit volunteers, according to the study.

How does this happen? Researchers looked at the data again in terms of who got exposed to the diary via notifications from others in the group. Once an obese person adopted the behavior, clustered networks allowed other obese individuals greater exposure. Scientists conclude that being in these similar clusters gave obese people more access to the behavior and increased their chance of adopting it.

"Our findings suggest that obese individuals may be more dependent than healthier individuals on the compositions of their social networks for making decisions about adopting health behaviors," Centola wrote in the study.

It remains an open question as to why this was the case among obese individuals, Centola told CNN.

"It was a way of clearly identifying how one feature of social structure could affect behavior," he said. "In terms of more substantive implications, there is more work to do."

This line of research suggests that policy makers might benefit from designing online social networks, and arranging the connections between people to reach certain goals, Marco J. van der Leij wrote in an accompanying Perspective article in Science.

soundoff (24 Responses)
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    December 2, 2011 at 19:19 | Report abuse | Reply
  2. FlopFlipper

    What are these "healthy behaviors" of which you speak?

    December 2, 2011 at 19:37 | Report abuse | Reply
  3. Billy

    My overweight friend says he doesn't feel comfortable going to the ice cream shop with me. He has no problem doing this with another overweight friend.

    December 2, 2011 at 19:49 | Report abuse | Reply
  4. Bert Bigdongle

    Pic would be better if they were naked.

    December 2, 2011 at 20:03 | Report abuse | Reply
    • Kellina O.

      Of course you don't know their ages do you? But that doesn't matter, you're jacking off in your mom's basement.

      December 2, 2011 at 21:14 | Report abuse |
    • Berts Mom


      December 2, 2011 at 22:16 | Report abuse |
    • Bert's Dad

      Don't pressure the boy, Margaret!!!

      December 2, 2011 at 22:57 | Report abuse |
  5. DA

    So we're supposed to select our friends based on body-mass index... Nice criterion. They can be jerks, cheat, steal, rape, murder, no matter, as long as they're not overweight. Now I've seen it all.

    December 2, 2011 at 20:07 | Report abuse | Reply
    • Nina

      Totally agree with you!! I've met a group of people(all friends) – all same size, but their behaviors are questionable. Rude, mean, no personalities... You might say "birds of a feather flock together."

      December 3, 2011 at 15:31 | Report abuse |
  6. Bob

    The brunette is cute. Just saying.

    December 2, 2011 at 21:32 | Report abuse | Reply
    • BCuro

      Yep. Those 2 friends can come play at my house any time they want.

      December 3, 2011 at 08:59 | Report abuse |
  7. Marnie

    Let's talk about the science – how are their findings anything other than classic conditioning? these weight loss groups all saw duplicate messages of an original notification due to being interconnected (5 people email the same story to you, makes it seem more powerful). Local phenomenon. Why are we surprised to be more easily conditioned by those we resemble (physically here, but can extend to mentally & spiritually)? In this case it was positive influence, but it can easily be negative – environment selects.

    December 2, 2011 at 21:46 | Report abuse | Reply
  8. MaximEyes

    Bob is totally right. I didn't even read this story. Both girls are hotties but the brunette is a breezy!

    December 2, 2011 at 21:53 | Report abuse | Reply
  9. ShowerFriends

    I do believe after this helpful workout they'll to shower off.

    December 2, 2011 at 23:03 | Report abuse | Reply
  10. jane

    These comments miss the point. The key finding is that obese people respond more strongly to being part of a social network. I'm a thin person who exercises and eats right(it's easy. I like in NYC) twice I've dated men who struggle with their weight. When we're dating, they get healthy, lose weight. When we're not, they go right back up. People who over eat are like people who struggle with alcohol; it's complicated and compulsive. Having someone close to them with good behavior seems to be an enormous help.

    December 3, 2011 at 02:32 | Report abuse | Reply
  11. sam

    drunks hang with drunks

    December 3, 2011 at 03:35 | Report abuse | Reply
  12. patsythomasz

    Reality TV can make it seem very difficult by over-dramatizing the time and energy needed to make a saving for you and your family, i always use websites like "Get Official Samples" to find free products and coupons

    December 3, 2011 at 05:17 | Report abuse | Reply
  13. cocdoc

    Hot Hot Hot

    December 3, 2011 at 09:00 | Report abuse | Reply
  14. tamara reina

    Let's hope our weight stay healthy boy those genes like my body

    December 4, 2011 at 09:27 | Report abuse | Reply
  15. santosh (bihar)

    i am too fat and drink a tine in a week. How can i be a slim& thin boy.

    January 11, 2012 at 20:42 | Report abuse | Reply
    • Aswathy

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      April 8, 2012 at 14:29 | Report abuse |
  16. Samuel Bogale Calgary Alberta

    Interesting article – I enjoyed reading!

    January 19, 2012 at 14:49 | Report abuse | Reply
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    January 28, 2021 at 22:27 | Report abuse | Reply
  18. Shantel Gloff


    March 6, 2021 at 15:10 | Report abuse | Reply

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