A recent story in the Irish Independent says that "if you want to stay thin, don't choose fat friends".
Apparently researchers have found that obesity is socially contagious - it spreads from person to person within the same social group.
A study of 12,000 people whose height and weight were measured repeatedly over 32 years has revealed that when one person gained weight those around them tended to gain weight, too.
Nicholas Christakis, professor of healthcare policy at Harvard Medical School and co-author of the study, said: "What appears to be happening is that a person becoming obese most likely causes a change of norms about what counts as an appropriate body size. "People come to think that it is OK to be bigger since those around them are bigger, and this sensibility spreads."
This is an angle on the issue of obesity that might interest those in the qualitative lab at Geary, and I think Michael will be interested in this research too.
Unexpectedly, the greatest quantifiable effect on the likelihood of individual obesity did not come members of the same family (who shared the same genes) or household, but from friends.
This seems to be provide evidence for a mechanism where peer effects influence health behaviour, without the nuance about how family backround can affect peer choice, as mentioned at the end of the previous post.
2 comments:
Very interesting stuff- check out the video on the Time magazine website- Obesity is contagious. It's interesting to see the way obesity is portrayed as a "multi-centric epidemic with many people influencing one another". The language and presentation is similar to that which I have seen used previously in the case of HIV. The picture in the indo with the man with his face in a kebab which could be laced with serious opiates by the look in his eyes is typical of the promotion of the obesity- gluttony stereotype. This study is incredibly interesting but I don't know why they are using this contagion angle as it is clearly promoting anti-fat bias.
I think the patterns are a result of the friends we choose as many of the 'clusters' seem to be due to the formation of new ties. What may be likely is that people select their friends based on similar lifestyles and over time physiological mechanisms such as those implicated in metabolism, change as a function of age and cause obesity in those who cluster together due to their choice of sedentary leisure activities. These people may also be most likely to experience the effects of larger standard portion sizes and increased fat content in meats. My own very basic analysis of sports interests of people on the social networking site bebo showed that there was a decline in similarity as you move to more distant connections (friend of a friend and so on) indicating that friends will cluster based on factors surrounding active or passive interests. I think this is a fertile ground for further analyses and incorporating aspects such as the extent or frequency of connection between people may help demonstrate this effect.
A process which may partially explain genuine co-influence is the
convergence theory of emotion which shows how emotional experience tend to increase in similarity between college roommates over time. Importantly evidence in emotional convergence theory suggests that over time those of lower status come closer in emotion to close friends of higher status but the effect does not work in the opposite direction. In regard to obesity we can infer that an indication of higher status may predict the direction of effects.
The finding from the study in question that "if your friend had not named you as a mutual friend, and you became obese, it would have no significant impact on your friend's weight" may tie in with this finding in that the individual who does not name you as a friend may be likely to be of a higher status and thus is not influenced by your behaviour.
This is similar to the debate in the alcohol research as to who is causing peer-to-peer drinking effects. A similar network analysis to this one, taken over time could yield some interesting results.
Michael,
I would be interested in reading about your analysis of sports interests of people on the social networking site bebo, and especially how you went about it. If you have a paper, or any document on it, I'd be interested in having a look at it.
The convergence theory of emotion is also interesting. I'd always thought that a peer with a depressive tendency would make an individual more depressed, but apparently not, if I read correctly.
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