A Few More Observations on the Fat Friends Study

It wasn’t a bad dream. Last week the global press was actually debating whether it’s ok to associate with fat people based on a study, which was published (and heavily promoted) by the New England Journal of Medicine. For those of you with the good sense not to follow this kind of news, the report purported to show that obesity spread from friend to friend by fat friends changing each other’s norms of what weights are “acceptable.”

Sandy Scwarcz and Kate Harding, among others, did a beautiful job of debunking this study’s conclusions from different perspectives (the former from a sciency perspective, the latter from a position of pure common sense).

So it’s been said, and said better. But I want to add just a few more things I’ve noticed about what’s wrong with this study. There are so damn many things wrong, that it’s easy to miss a few.

Friends and Relatives

First, you couldn’t have picked a group of “friends” that were more likely to be genetically related if you made a concerted effort. Both the subjects and their “friends” were all children of the original Framingham Heart Study cohort, so their parents were all living in Framingham, Massachusetts sixty years ago. The “friendships” analyzed were narrowed to people who a) this group listed as contacts, b) were also in the Framingham heart study, and c) were not first degree relatives.

In other words, these “friends” were very likely to be second and third degree relatives – cousins, aunts and uncles – and my guess would be that the more likely they are to list each other as mutual contacts, the more likely they were to be related.

Genetics Doesn’t Work that Way. Really.

The researchers wave away the general possibility that genetic similarities could have influenced their results by making a fundamentally wrong assumption: that genetics is a single, static effect. Which is why they believe that adjusting for initial weight excludes the possibility of genetic similarity as a factor in weight change as the decades go by.

I can’t emphasize enough how critical that assumption is to their entire analysis. And how wrong it is. Different genetic effects influencing weight kick in at different points over the lifespan from infancy to old age. So, for example, two relatives with totally different BMIs in young adulthood could share genes that make them both prone to gain weight or distribute it in a certain way in middle age or prone towards frailty in old age.

So that’s a simply wrong understanding of the genetics of weight regulation that underlies their entire analysis (and has a lot to do with their not being obesity researchers).

An elaborate hypothesis covers a multitude of evils

The other obvious problem, which Kate Harding and Sandy zero in on, is that their complicated data analysis spat out downright bizarro results:

  1. At the start of the study, having a fat friend actually reduced your chances of being obese (They call it the “Laurel and Hardy effect”).  In fact only weight change, and not fatness or thinness per se, had any positive association between “friends.” (To discover this interesting detail you had to look in a supplementary appendix which needed to be downloaded separately). 
  2. People who listed each other as contacts (defined by the authors as “mutual friends”) were more likely than any other relationship to have a correlated weight change. But only among men.  Female friends didn’t have a significant impact on each other’s weight change.
  3. Opposite sex friends and opposite sex siblings didn’t have a significant impact on each other’s weight change.
  4. Same-sex siblings, spouses and nonmutal friends all seemed to have some impact on each other’s weight change but the difference in impact between these groups doesn’t appear to be significant.
  5. Neighbors don’t impact each others’ weight change.
  6. Geographic distance has no importance. So the impact is the same if your “friend” lives with you, next door, or 3000 miles away. So apparently eating meals together or sharing recreation have no influence on weight change.

It’s a mess. My first impression – and I think the impression of common sense — is that all this is an artifact of the methodology (which is researchese for “you did it wrong.”)

Instead, what the authors did was come up with a flexibly vague, elaborate and speculative hypothesis to try and explain each of the details of the mess.

Here’s how it goes: apparently friends in 1971 had different-sized friends because fat friends like to be with thin friends, and vice versa. This changed in the intervening years because: “Whereas obesity has been stigmatized in the past, attitudes may be changing.” One of their two citations for that unlikely assertion? An article on the size acceptance movement. No, I’m not kidding.

So apparently over the next thirty years as one man falls prey to the nefarious influence of NAAFA (in Framingham Massachusetts, where I happen to know nobody’s ever heard of NAAFA – it ain’t no Northampton)….other male friends say to themselves “hey, I guess it’s OK to be fat.”

Opposite sex friends and siblings are immune to each others’ influence because they don’t see each other as role models. Apparently female friends don’t either. Spouses and siblings take fewer cues from each other than friends do. Shared behavior or shared environment have no role whatsoever because…well they just don’t.

It’s a lot to swallow. Or, Occam’s razor: They did it wrong.

Because It’s Just Not Directionality if it’s Not Significant

The authors make a LOT of the “directionality” of the effect, claiming friends who list you as their friend are less likely to impact your weight than friends whom you list. In other words, you’re more likely to take cues from people you think of as friends than people who think of you as a friend.

That direcionality, they argue, rules out the possibility of confounding variables, and is pretty much the sum total of their justification for arguing that this is about influencing attitudes, and has nothing to do with genetics or anything else.

And that would be interesting. If the “directionality” were statistically significant. But it’s not. The researchers don’t actually admit this, but you can basically eyeball it just by looking at the overlapping confidence intervals for the two types of friendships.

It’s hard to imagine that the entire thesis of an article in a peer-reviewed medical journal is based upon a result that is statistically meaningless. But that appears to be the case.

10 Responses to “A Few More Observations on the Fat Friends Study”

  1. Meowser Says:

    Great work, Fu. Yeah, NAAFA claims tons (pun absolutely intended) of the male population in Framingham, doesn’t it? Talk about grasping for straws. (OK, I promise I’ll stop with the bad puns).

  2. bstu Says:

    Its amazing how these studies always find the time to explain away inconvenient results but never even ponder for a moment alternate explanations for the results they were looking for. I guess since they were looking for it, obviously it doesn’t need to be explained away. Science is all about finding the result you intended to, after all, as opposed to discovering the result that exists.

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  4. Laura Says:

    There is no doubt that if you are thin and start hanging with overweight friends, this will have an impact on your life. You will be treated worse, because most heavy women are viewed as not caring about themselves and most are so depressed that they don’t take the extra time to care. I’m thin and well aware of who allow into my life and how it relates to me. I dislike blaming others, but heavy friends tend to eat more, more often and do less physical activity. Just be aware of the people in your life. Fat or thin, they are making an impact on you and your life.

  5. vesta44 Says:

    Laura – Just because fat women are viewed as not caring about themselves doesn’t mean it’s true. I happen to be a fat women who cares very much about myself. Don’t buy into the stereotypes that fat women are slobs, overeat, and don’t exercise. It’s not necessarily so, and even if it is, no one died and made you the boss of the universe to have the right to judge them. Placing the blame on fat women for your prejudices does a disservice to you and to the fat women that you refuse to have as friends. Studies have shown that fat people don’t generally eat any more than thinner people, so saying they eat more is an excuse to exclude them from your life. I’m not saying you have to have to have fat friends, but you’re going to miss out on meeting some fabulous people if you base your friendships on looks. I had a friend who was a multiple personality and had tons of problems because of that (and she was fat too). I could have excluded her from my group of friends just because her problems could have caused me a lot of problems, but I didn’t (and I’m so glad I was open to the friendship she offered, she ended up being my best friend, and when she died, it devastated me). We had a lot of difficulties in our friendship, when through a lot of hell together, and she had a tremendous impact on my life (good and bad). But I’ll tell you what, I wouldn’t have missed any of it for all the money in the world. I’m a smarter, wiser person for having known her.
    There is no way to know ahead of time how a person’s friendship is going to impact your life, and it doesn’t matter what the person looks like, you still aren’t going to know all the ways they will affect you. Shutting yourself off to those experiences can stunt your growth, mentally, emotionally, spiritually, etc.

  6. Meowser Says:

    Thank you, Vesta, your response was a lot classier than mine would have been. “I can’t hang out with X type of person because people will think I’m X type of person too” is a kind of reductionist thinking best left behind by the time you turn 13. Even if I was thin, I still wouldn’t be neurologically typical; does that mean NT people should avoid me like the plague because they will be tainted by association with the neuroatypical? Unfortunately, many people would say “yes,” but that’s no excuse for continuing to perpetuate it.

  7. wriggles Says:

    I couldn’t care less whether fat people eat more or less on average than anyone else. If you are stupid enough to believe that the content of one’s character is in inverse proportion to their weight, that says more about the state you’re in.

  8. Lexie Says:

    I saw the news report that stated that fat friends will make you fat. Geez, way to make fat people even MORE unpopular. And… if you haven’t noticed, it’s kind of a no brainer. Hanging out with alcoholics may result in you drinking more. Hanging out with drug users may result in drug use. Duh! Thank you news for this wonderful discovery! What a great way for people to blame their weight gain on someone else. “O my God, I gained five pounds. It’s all Lexie’s fault! She’s so fat!” Why can’t people just take some responsibility for themselves?!
    I wrote a letter to my local news station on this in fact. And here it is:
    Dear Fox News,
    I am an 18 year old girl who is overweight and heard Thursday, July 26 on your 6 am news that obesity is contagious. This may be a study but I would like to know how insensitive you have to be to report such a thing! This is no less than another form of prejudice, just like racism and sexism and every other kind of nasty thing that hurts good people and the public. Does this report not apply to anyone and any vice? If someone has an anorexic friend (which is quite similar to obesity mind you, it is not the opposite that people believe) would he or she not be more at risk for becoming anorexic? Or if someone had a friend who was an alcoholic or a drug user? And don’t you believe that people are the writers of their own fate- if a healthy person becomes overweight, it is not their overweight friend’s fault, it is their own. I’m sure there are a lot of social and “health” reports that you do not air because they maybe offensive- I am announcing to you that I have been offended. Reports like this put people at risk- young children are struggling with their self image and the image of “perfection” and news like this brings their attention even more than it already is to being what the media portrays as “perfect” and fitting in which could lead to eating disorders. Don’t you think it’s already hard for someone like me to make good friends? To feel comfortable in social settings? Thank you for now turning the public’s attention back to people like me, good people who happen to be overweight- you seem to do this quite often. It’s hard enough to be a kid, it’s harder to be different!
    What good came out of reporting such a study? How does this help anyone? Should people limit their time with overweight people like they limit their time on the computer or watching TV? Wouldn’t a study on the effects of computer addiction because it, all-in-all, would effect more people (from the addict to the friends and family of those), be more useful to the public? What does this report do but make us as a society more self-conscious and narrow-minded?
    Ironically, when I heard this news report I had just gotten home from an hour at the gym. Just because people are obese does not mean they are always eating and this never seems to be pointed out, it seems that the general consensus is that if you’re fat all you do is eat.
    Please show the same sensitivity to ALL people- people of race, religion, sex, orientation, and even weight. We are humans, like you; we are not just fat.

    They never responded.

  9. Wednesday Round Up #26 « Neuroanthropology Says:

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