Is Obesity Contagious?

Science News reports that a 2005 study of obese and normal-weighted people found that “30% of the obese group showed signs of previous adenovirus-36 infection, while only 11 percent of the lean group did”. Recent research showed that the virus induces long-term changes in how stem cells develop, causing some that were slated to form bone cells to turn into fat cells instead. Researchers are quick to point out that you shouldn’t avoid fat people for fear of infection because the infectious phase only lasts a few weeks, and would have ended long before obesity set in.

I am pleasantly surprised though that the media hasn’t latched onto this as a convenient explanation of the obesity epidemic of the past 30 years. There is an overwhelming avalanche of data that supports the argument that obesity in most cases comes from a combination of eating the wrong foods, eating too much of it, and not exercising enough. Yes, there is a genetic component that predisposes some people more than others, but like the viral explanation, genetics is not determinant but rather it’s just one factor.*

It turns out though that there is a major infectious component to obesity: it spreads through social networks via the mind. The July 26 issue of the New England Journal of Medicine documents findings that between two people who consider each other friends, if one of them becomes obese, the other’s chances of also becoming obese increase by 171%. The effect occurs whether you live next door to each other or 500 miles apart, so the viral explanation seems unlikely to account for the contagion. Also, neighbors who don’t consider themselves friends, and friends (and siblings) of opposite sex don’t affect one another. Same-sex friendship seems to be the only factor in social contagion of obesity. And lest you think it’s a matter of selecting friends who look like you (i.e. correlation vs causation), they controlled for that too.

Turns out obesity is a powerful meme, which suggests that it’s not enough to target individuals if you want combat the epidemic effectively. On a cultural level there must be acknowledgment of the social component to obesity, and there must be campaigns to immunize our vast social network against its spread. The way you stop bad memes from propagating is by a combination of centralized propaganda (i.e. traditional media blitz) and deeper one-on-one communication between individuals (i.e. create a virulent anti-obesity meme).

Spread the word.


* Similarly, there are people who for various reasons can eat all the wrong foods or ridiculously large quantities and not gain weight. Some of the mitigating factors are genetics, adenovirus-36, the amount of exercise one gets, and the total diet one eats (e.g. acidic foods can slow digestion of simple carbs making them less likely to trigger insulin resistance, a major contributor to obesity). For anyone who wants to learn about how to eat healthy and enjoy your food as much or more than you do now, I highly recommend checking out Dr. Ann’s website and book.

  • The “viral hypothesis” is provocative but should not serve as a distraction from the forces that have already been scientifically substantiated to be driving the obesity epidemic. This gargantuan public health debacle can be largely attributed to the simple interaction of a toxic and highly permissible food environment (that is completely at odds with our ancient, hard-wired instincts to eat when food is available) with a culture where movement is no longer required for basic survival.

    This reality is further exacerbated by relentless cradle-to-grave marketing of highly obesigenic fare like fast food. I single out fast food because it is the “perfect embodiment” of virtually every single feature that science has shown increases caloric intake – namely it’s low in fiber, big in portions, high glycemic, high caloric density makeup. It’s also cheap, convenient and everywhere. And just when it looked like things were improving, McDonalds is “reintroducing” its super size menu albeit with more “socially” acceptable names (McDonalds suddenly removed the super size option a few years back after the release of Morgan Spurlock’s “Super Size Me” documentary). The new options include the 42 ounce Hugo soft drink (400 calories) and the 1/3 pound Angus burger weighing in at 820 calories and 43 grams of fat if you add the bacon. If you include a large fry, you can get a 1700 calorie meal which is just a bit below what the average American should be consuming over the course of an entire day. Given the fact that consuming a surplus of a mere 100 calories a day translates to 10 pounds of weight gain yearly, it’s a wonder we are not worse off.

    We all need to be more vigilant in voting with our knives and our forks. Personally, I take it one step further and vote with my feet by never stepping foot in traditional fast food outlets.

  • Pingback: Food for Thought (or thought for food?) « Envelop()

  • Pingback: Behavior and Emotions as Virus « Complex Adaptive Systems()