Study of the Day: Among Groups of Friends, Obesity Is Contagious

More

When it comes to obesity and related behaviors, new research suggests that what you weigh is in part influenced by who your friends are.

obesity header.jpgglennharper/Flickr

PROBLEM: Other research has observed that obese students tend to run in the same social circles. Is this just a case of like attracting like, or might there be social influences at play?

METHODOLOGY: David Shoham and a team of researchers at Loyola University revisited the National Longitudinal Study of Adolescent Health from the mid-1990s, applying a sophisticated form of statistical analysis to data collected from students at two large high schools. Taking into account the adolescents' body mass index (BMI), time spent in front of television and computer screens, and participation in active sports, they isolated social influence from factors like homophily (the tendency to bond with people similar to oneself) and shared environmental influences and measured its influence on obesity and related behaviors.

RESULTS: Students who were borderline overweight were 40 percent more likely to decrease their BMI over the course of the school year if they reported having lean friends, while similar students were 56 percent more likely to show an increase in BMI if their friends were obese. In one of the schools, social influence was shown to affect screen time, and in both schools it affected the playing of active sports. Homophily, on the other hand, was not correlated with screen time in either school, although it was linked to the playing of active sports in one.

CONCLUSION: Social influence, along with homophily, plays a significant role in weight loss and weight gain.

IMPLICATION: While Shoham points out several limitations of the study -- the data is self-reported, and it comes from the dark ages before online social networking -- this new emphasis on social influence indicates that weight-loss strategies may need to look beyond the individual. It also underscores the importance of prevention: students showed a greater tendency to gain weight among obese friends than to lose weight among thin friends. While there's a lot that needs clarifying about how social influence actually functions in this context, these findings suggest that its power can be harnessed in efforts to combat obesity.

SOURCE: The full study, "An Actor-Based Model of Social Network Influence on Adolescent Body Size, Screen Time, and Playing Sports," is published in the journal PLoS-ONE.


Jump to comments
Presented by

Lindsay Abrams is an assistant editor at Salon and a former writer and producer for The Atlantic's Health Channel.

Get Today's Top Stories in Your Inbox (preview)

A Fascinating Short Film About the Multiverse

If life is a series of infinite possibilities, what does it mean to be alive?


Elsewhere on the web

Join the Discussion

After you comment, click Post. If you’re not already logged in you will be asked to log in or register. blog comments powered by Disqus

Video

The Death of Film

You'll never hear the whirring sound of a projector again.

Video

How to Hunt With Poison Darts

A Borneo hunter explains one of his tribe's oldest customs: the art of the blowpipe

Video

A Delightful, Pixar-Inspired Cartoon

An action figure and his reluctant sidekick trek across a kitchen in search of treasure.

Video

I Am an Undocumented Immigrant

"I look like a typical young American."

Video

Why Did I Study Physics?

Using hand-drawn cartoons to explain an academic passion

Writers

Up
Down

More in Health

Just In