You will be fat if friends in your social network are fat. Really?
It seems anecdotal - either completely obvious or an urban myth, but Nicholas Christakis and James Fowler show this in their study, "The Spread of Obesity in a Large Social Network over 32 Years", published in this week's New England Medical Journal (NEJM).
The authors used data from the Framington Heart cohort to quantify what many people take as a given, that people who associate with fat people are more likely to be fat, as Christakis explains in this video from Harvard's Office of Public Affairs. According to their research, obesity spreads via social clusters that extend to three degrees of separation. Subjects who had a close friend who became obese within a particular time interval increase their own chances of becoming obese by 57%. An obese spouse would increase their chances of becoming obese by 37%, and an obese sibling would increase their chance of obesity by 40%.
The authors document "a higher order effect", "a spreading process through the network", or "a cascade", whereby the fat begets fat, or as Christakis put it, "like an epidemic, a real epidemic". This study acknowledges genes but targets environmental factors too. For instance, they found found that mere proximity doesn't necessarily influence obesity. If your next door neighbor is obese, this won't influence your own chances of obesity, and thus they say, "local" environment doesn't matter.
"Our findings that the weight gain of immediate neighbors did not affect the chance of weight gain in egos [primary subjects] and that geographic distance did not modify the effect for other types of alters (e.g., friends or siblings) helps rule out common exposure to local environmental factors as an explanation for our observations."
But what might "local" environmental factors of obesity be? Intuitively, we surmise there's nothing unique about Framingham or Massachusetts, obesity-wise. That is there's no rural diet these days that differs significantly from the the urban diet, no Southern diet radically different from a Northern Yankee diet. Sure maybe you can find grits more easily in the South, but local traditions have usually been replaced by global alternatives.
The old-fashioned soda-fountain has been replaced by McDonald's. Fast-food habits aren't local, nor are habits of allaying thirst with Coca-Cola. Watching TV for 4 hours a day isn't a local habit. Nor is the propensity to drive endlessly around parking lots vying for a parking space less than fifteen paces from the mall entrance.
These not-so-local habits make the jobs of photographers tasked with capturing footage for the ubiquitous evening news about alarming obesity trends easier every day. It is a "real epidemic", but how far does the language of disease get us? Sure it may be interesting to acknowledge that friends and family influence your perception of acceptable weight, as well as what you eat, your religious preferences, voting habits and almost all other choices or beliefs. But does this add meaning to the dilemma or is it just comfort food?
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In the end, the authors predict that people get fat together, therefore they'll get thin together, although in the study, there was a (to be expected) preponderance of weight gain. A seemingly obvious solution is to unfriend your fat friends, but the authors say no, no, no! -- don't "get rid of" any friends, since research "suggests" friends are good. What to do then, with this health fad, this obesity meme? As we all know, change is the tough part. We've already tried various flawed experiments to clamp down on the trend.
Cristakis concludes in his video that "interventions that target groups of individuals rather than sole isolated individuals are likely to be more effective". Aha! Like so many CDC recommendations? Trans-fat legislation? We'll institute more gym. Not possible? Cristakis manages to cover all bets with his third point, "to the extent that prevention or treatment of weight gain in one person works, you're more likely to contribute to avoidance of weight gain in others."(Image source: http://commons.wikimedia.org/wiki/Image:Soda_jerk_NYWTS.jpg)
Related posts at Acronym Required:
Common Sense Food in Schools
"Why So Fat? It's Systemwide",
"Childhood Obesity, The American Way"
"Survey Says: Pop's Out Drugs are In"
"News of Lightweight Study: 'Obese Should Walk Slowly'"
"Coke: Teaching the World to Sing"