Fat Is Contagious!

I don't even have it in me to do a full-on rant about a new claim that obesity can be transmitted through social networks, which was apparently published in the New England Journal of Medicine today. Earlier, someone sent me a copy of the entire article -- which does not seem to be available on the NEJM website, but presumably will be at some point -- and these were my gut impressions:

1) Geographical distance did not decrease the risk of "social" obesity here. That point is made over and over. Which means they are claiming that by TALKING TO EACH OTHER -- not living with each other or eating together or exercising together -- people are making each other fat.

For this to be plausible, you need to accept a few things:

A) Geographically distant friends and relations spend enough time talking about their weight to produce this effect.

Does that seem even remotely realistic to you? When I call my far-away friends, fat or thin, I ask about their lives and families, not their bodies.

B) There is an identifiable set of behaviors that reliably leads to obesity, which can be discussed and encouraged over the phone or by written correspondence.

Presumably, they think that's eating too much and not exercising enough. Problem is, as we've discussed before, it's just as hard (i.e., near impossible) to make naturally thin people permanently fat as it is to make naturally fat people permanently thin. So even if people could talk their friends into chronically eating too much and exercising too little -- which, come on, people -- the results would almost certainly not last any longer than the results of the typical "successful" diet. Unless that person was already predisposed to being fat and started out below her natural set point -- maybe because of, um, dieting. Hmmm....

C) People are more likely to take one geographically distant friend's word for it that engaging in [undefined set of behaviors that ostensibly lead to obesity] will be more personally rewarding to them than conforming to the OVERWHELMING insistence from the larger culture and, most likely, their local environments (in which their bodies are actually seen and judged) that fat is bad and dieting is good.

Can anyone seriously believe all three of those things?

2) Obesity, according to this study, is more socially transmissible from one man to another than one woman to another.

Does this jibe with other research that suggests women are much more invested in social networks, more communicative with their friends about personal issues and, not for nuthin', more susceptible to mirroring their friends' eating behaviors when they do eat together?

3) If they're going to include siblings in their results, they REALLY better have completely ruled out any genetic component to fat, which they clearly haven't.

The fact that they would include people with genetic overlap in a study that purports to be all about social factors strikes me as utterly absurd -- I think it's more than fair to ask why they included that group at all. Because their results were statistically insignificant without it, perhaps?

4) As I understand it, spouses did not "affect" each other as strongly as even geographically distant friends.

This goes back to point 1. Are we really meant to believe that people in one of the most intimate possible relationships, who communicate daily, eat together, and share umpteen "lifestyle" factors, are less likely to "transmit" obesity to one another than friends who live on opposite coasts? What is it that makes you fat, then? If we believe it's diet and exercise, how is it conceivable that people who live together do not affect each other's diet and exercise habits as strongly as pals who rarely see each other? And regardless of what they're claiming the direct cause of obesity is here, do we really believe that people are more susceptible to the opinions of distant friends than their own spouses?

5) All of this is based on data from the Framingham Heart Study. (That link is to several excellent articles by Sandy Szwarc that reference this study.)

It's well worth mentioning that that study demonstrated, among other things, that there's no clear link between longevity and BMI, that among non-smokers, obesity was correlated with greater longevity, and that the largest single determinant of longevity was... drumroll... genes.

So basically, they took a study that showed obesity's no big deal and turned it into a study that shows obesity is CONTAGIOUS!!!

*headdesk*

6) They repeat yet again that obesity is increasing like crazy, it's out of control, blah dee blah. They don't cite the statistics, which are far less alarming than the myth that we're all blowing up like balloons. (One oft-neglected point: we're also getting taller.) The discussion of "Claim 1" in this paper (PDF) breaks down why they're freaking out over nothing (emphasis mine):

The claim that we are seeing an "epidemic" of overweight and obesity implies an exponential pattern of growth typical of epidemics. The available data do not support this claim. Instead, what we have seen, in the US, is a relatively modest rightward skewing of average weight on the distribution curve, with people of lower weights gaining little or no weight, and the majority of people gaining ~3-5 kg more than they did a generation ago. The average American's weight gain can be explained by 10 extra calories a day, or the equivalent of a Big Mac once every two months. Exercise equivalents would be a few minutes of walking every day. This is hardly the orgy of fast food binging and inactivity widely thought to be to blame for the supposed fat explosion.

While there has been significant weight gain among the heaviest individuals, the vast majority of people in the "overweight" and "obese" categories are now at weight levels that are only slightly higher than those they or their predecessors were maintaining a generation ago. In other words we are seeing subtle shifts, rather than an alarming epidemic. Biologist Jeffrey Friedman offers this analogy: "Imagine that the average IQ was 100, and that five percent of the population had an IQ of 140 and were considered to be geniuses. Now let's say education improves and the average IQ increases to 107 and 10% of the population has an IQ of >140. You could present the data in two ways. You could say that the average IQ is up 7 points or you could say that because of improved education the number of geniuses has doubled."

So the whole premise that justified this review of another study's data -- that we, as a country, are SO MUCH FATTER than we used to be -- is basically horseshit. There's that.

Finally, it sounds like what they're really afraid of is people telling their friends it's okay not to diet. If that's what's actually happening here? I hope it becomes a goddamned epidemic.

(Cross-posted to Shapely Prose.)