December 2nd, 2011
06:00 PM ET
Who you know influences how you behave, a growing body of research is showing.
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.
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Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.