Tuesday, September 20, 2011

Obesity Contagion? Debunked Again.

Another critique recently came out of the now-famous (and infamously irritating) obesity-is-contagious study, which was all the rage in the media a few years ago. This research was published despite the common sense notion that homophily or the tendency for people to associate with people like themselves, was both a more obvious and rational explanation for why people in the social networks of fat people might also be fat. (For example, I share 90 friends with Marilyn Wann on Facebook--fat people and fat activist folks are literally my largest social network.) 

The first critique, in 2008, used the homophily argument. And there have been others. It seems there is a mass of work building which debunks the obesity-is-contagious silliness. The latest critique looks at the statistics and statistical models used by the the researchers. According to Indiana University Math Professor Russel Lyons':
"The problem is that their methods were deeply flawed from bottom to top: The models used to analyze the sparse data contradict the data and the conclusions, and the method used to estimate the dubious models does not apply," he said. "The statistical significance tests that were applied to the questionable estimates do not show the differences they have proposed."
There are a couple notable items in the article I link to above, which speak to the state of science and health research in particular. First, one of the obesity-is-contagious researchers had a profit motive:

"Christakis built on his research to form a company, MedNetworks, which proposes to help pharmaceutical companies get doctors to prescribe more of their drugs"
As if doctors didn't already have enough pressure from pharmaceutical companies on prescribing medicine. Maybe they should do a study on that sort of contagion

Second, Lyons' experience makes it clear that--although it's sometimes easy to publish crap research like the obesity-is-contagious study--publishing critiques of popular and widely celebrated research, if that research supports the status quo and the fat panic paradigm, can be quite difficult to publish. According to the article,

"Both of the leading, prestigious journals that published research by Christakis and Fowler -- the New England Journal of Medicine and BMJ (formerly British Medical Journal) -- rejected Lyons' critique, the first declining to give a reason and the second saying the work would be better placed in a specialist journal. Rejections then came from three other leading journals on the grounds that they had not published the original research. A statistics review journal rejected Lyons' paper on the basis that the original research of Christakis and Fowler was itself not sufficiently important."
 What does Christakis have to say about it all? According to the New York Times article, he doesn't say he was wrong but skirts the issue by chalking it all up to the scientific process.

"“This is how science proceeds,” he said. “We came up with a fact that no one ever thought about before. We published our methods. We published our data. We said, ‘Look, we think this is important. You should help us figure out how to do this better.’ ”
He's not wrong, exactly. The point is to do science, duplicate it, test it, critique it, make it better and do it better. Though he kind of leaves out the critique part, and his words leave me with the sense that he thinks people should be helping him better prove obesity contagion rather than proving him wrong.

I'll leave you with a quote, which I think is apt:
"I know that most men, including those at ease with problems of the greatest complexity, can seldom accept even the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have delighted in explaining to colleagues, which they have proudly taught to others, and which they have woven, thread by thread, into the fabric of their lives." -Tolstoy


  1. Are you on my facebook? :P You're completely right- us fatties just like to hang out ;-) I add people whom I have things in common with. by the logic of this study atheism, veganism, and feminism would also be contagious. That's the problem when you do research to find *your* answer rather than an objective one.

  2. Heather, I don't think I'm on your Facebook, but I wouldn't doubt we have similar friends!

    This idea of social contagion is really popular with folks who study networks, but to dub it "contagion" contributes to the pervasive problem of medicalization. "Do you suffer from inadequate eyelashes? Try Latisse!" What these people were hoping for, obviously, was to not only frame body weight as somehow transmissible, but also to use that as a vehicle to sell medication. Medicalization is never an innocent act, at least that I have seen.

  3. Heather's on my FB page, y'all should link-up! Woo!