July 26, 2007

Obesity is "Socially Contagious"

So this study of obesity and social networks is pretty darn intriguing. Cranky Fitness will no doubt be among many other blogs writing about it today--but if Crabby can't the be first, at least she can be the silliest! Anyway, here's the bottom line: if your friends are starting to pack on the pounds, watch out--you may catch "obesity" from them.

Seems unlikely, doesn't it? But the effects of social networks, especially same-sex friendships, were extremely powerful when it came to subsequent weight gain (or, more optimistically, weight loss).

The actual journal article cited above is somewhat impenetrable, though it is has really cool charts, and diagrams of social networks that make them look like creepy organisms that could infect and kill you. So go there for hard core analysis.

Crabby is no scientist, but it looked like these guys thought things through pretty well, and controlled for factors like people's possible tendency to choose friends of their own size, or quit smoking at the same time.

However, for the less hard core, there's a watered down USA Today version that's much easier to follow.

Anyway, the clever researchers, James Fowler from UCSD (go Tritons!) and Nicholas Christakis from some medical school or other in Boston, took a fresh look at the Framington Heart Study data. Framington is that ginormous study that's been going on forever (well, 32 years). From that they could look at both social networks and weight gain (or loss), and here are some of their findings:

A person's chances of becoming obese increased by 37% if a spouse became obese.

The chances of becoming obese increased by 40% if a sibling became obese.

They increased by 57% a friend became obese. And the mutuality of the friendship made a difference: between mutual friends, one friend's obesity increased the other's risk by a whopping 171%.

No effects were seen between neighbors.

And those of the same sex had a greater influence on each other.

Christakis explained that "at the heart of the matter is the sharing of acceptable norms for weight, not just sharing the same eating-and-exercise habits... If someone you care about gains weight, your notion of an acceptable body size may change. You may decide it's OK to go up a couple of sizes."

But here's the icky part of this whole thing--the conclusions some people are drawing. According to the USA Today article, an obesity researcher at Baylor advises: "if you are trying to lose or control your weight, pick your friends carefully. You may not want to be around people who are gaining weight or who are too heavy."

Now that's just not nice.

Crabby suggests that instead of being a total jerk and cutting your overweight friends loose, that you simply use your brain. Make an effort to realize the impact their weight may be having on you, and don't use their larger size as an excuse for an extra slice of pizza or a "Baconator" with a large order of fries.

And you could also perhaps realize that your own efforts to eat healthy foods in reasonable portions, as well as your commitment to exercise, might be helping your less health-minded friends! Crabby prefers this approach to fleeing in terror from your friends lest they infect you with Contagious Obesity.

So what do you all think? Are your fat friends making you fatter? Are your skinny friends making you skinnier? Or are you impervious to the effects of your social network?


  1. When I first heard of this, I thought that it does make sense in some ways, but then I read the overflow information, such as what you point out about choosing your friends more carefully. Uh. No.

    I am encouraged when I look at my 18-yr-old daughter and her friends. We have some quite thin and petite (naturally, not disorder induced) girls, we have some girls with curves, and we have some girls who may be considered a bit on the heavy side but what is encouraging to me is that they all seem very comfortable in their bodies. That's what we need. Strong, confident women.

  2. It's a very interesting study, no doubt, and seems pretty rigorous. In the social circle with whom Hubby & I spend most of our time, everyone is generally normal weight. I have one friend who is obese. She has been generally supportive through my weight loss journey lo these past 7 years, but it hasn't seemed to affect her much one way or another. She is the manager of a Lane Bryant store and seems to enjoy introducing me with "Can you believe she & I used to be the same size?!"

    I think other studies have found we tend to eat more when we eat with others, so this may be a good reminder to watch portions especially carefully when we're with our heavier friends.

  3. I just read this and sent it to a (skinny) friend of mine with all my comments on it. I was largely wondering if I need to spend more time with my skinny friends, or something.

    And then honestly, it's confusing because I've very, very short (4'11") and was basically built to be very small (until I doubled my body weight through the evils of medications and the like and then lost a lot) But I often think my friends are all much smaller than me, yet they wear bigger sizes, which they think makes them fatter than me. And when it all comes down to it, that while I do wear about a size 6, I'm obese and need lose about 40 pounds to be a healthy weight. So that's kind of crazy.

    Really I think most of my friends are about "average". Not super skinny but not obese. (and in my mind smaller than me). My younger brother has always been the really skinny one in the family, if only he were female, maybe I'd lose some weight? ha ha.

  4. Well, it's harder for me to eat well when I go out with my friends who are larger than me as they don't really eat healthy. Example- went out with my thin brother (matabolism of a methed up roadrunner) and his wife (who is ~300lbs) for a walk last night. On their whim, we stopped for ice cream and I had some even though I'd just eaten...they called it a "treat", and as I had run that morning I said OK. It was yummy - don't get me wrong.
    But I've seen what being married to my brother does for you...his wife eats a lot, and with noone to call you or slow down it doesn't help. She's been trying to loose weight for ages...I really think portions can be a problem with no "normal" reference for comparison. If my partner and close friends all ate badly and didn't exercise I'd have a lot more problem sticking to healthy life...I like food too much and have problems with portion size. It'd be so hard to work out and not get anywhere healthwise being around people who unconsciously sabotaged their friends.

    I think if you like yourself and are comfortable in your own skin that is a start. As long as your companions don't make you feel bad or crave food by eating stuff you like that is really bad for you in front of you when you're trying to diet. For a foodie like me it's like smoking in front of someone who is trying to quit...

  5. "But all my friends are doing it!"

    Please. Enough is enough. I agree, to a degree, the people you have in your life do influence your health in subtle ways. But if you are properly grounded within yourself you'll be who you are and take care of yourself. Frankly, the obese friends business is just a happy excuse.

  6. Marijke,
    That's great news about your daughter and her friends. Sounds so healthy! I'm with you: lets encourage more strong confident women.

    Eh... not so much,
    That's great that your friend is so supportive of your journey even though she's not on it herself.

    I tend to eat more in social situations--I'm usually way ahead of my heavier friends in having seconds. I'm probably a bad influence on THEM, even though I eat much more reasonably at home. Good thing I don't get out much!

    Hi Meg,
    Maybe it's just my imagination, but I think it would be a little harder to stay slim if you're short--just because it seems like with a smaller frame you'd need slightly fewer calories, on average, and your portions might then need to be slightly smaller. And yet we all look around us to see what a 'normal' portion size is.

    But this is a screwball theory I just made up. I'd be curious to see what other short people might think about calories/portion sizes being affected.

    Hi geosomin,
    Interesting about your sister in law--I'm sure she knows intellectually that she doesn't have the metabolism to get away with what your brother does, but it must be hard not to feel "entitled" to a treat if he's having one. Good thing you have a healthy partner and friends--I think it really does make a difference.

  7. Sorry I missed you, leah!

    Good point about needing to be your own person and not look to others.

    But I think it's interesting how much of this may be subconscious rather than conscious. I don't think people are necessarily making conscious decisions to mirror their heavier friends, they're just doing it. So even studies like this may be a bit helpful in calling peoples attention to the choices they don't even realize they're making.

  8. Oh geez, that was probably to be expected, but I've just finished blogging about that as well! XD

    So, well... There is *some* truth to the fact that we have to bear the impact on our acquaintances, and I agree that the study itself is interesting, but seriously, I consider that poop-propaganda more than anything else. And all the more if the only 'good' advice to get out of it is "pick your friends carefully, avoid the fatties". I don't know yet if I need to throw a barf party or not, but this is just dumb.

    As for my own reaction to my friends' behaviours: I know obese, overweight and thin people overall, and I still consider that it's my body, my choice, my decision about what to put in my mouth. What, my *skinny* male friend likes eating at McDonald's, does it mean I have to ditch him as well because his bad habit is gonna rub off me?

    Yeah, barf party time, it is.

  9. Really, it's probably a lot like any group having a similar thing that binds them. But anyway, :-) what I really wanted to say was while on my daily 7 mile run today along a country road through the woods, I was 'meditating', suddenly I hear a HUGE crash as a tree fell off to the side of the road. Maybe I didn't solve the old philosophical riddle but it sure scared the heck out of me! I did, as I've now named, a quick 'crab' step to the side!!
    Thank you for listening :-)

  10. Heh, you know, there may be actually something to this... I have a dear and very petite friend in another state who told me recently that she had put on almost 10 lbs. (that's a lot when you're barely 5'). Maybe it's because I'm putting on the pregger weight?

    Although, my best friend who lives here told me she's happy because she hasn't gained any weight since I've been pregnant. But maybe she has been making more of a conscientious effort.

    So... not only should you avoid overweight people but also pregnant people, hehehe. ;)

  11. well, i guess us fatties just need to stick together. i can understand how difficult it is to loose weight when you have no support system, but to blame your weight on you friends is nothing but an easy out. we need to learn to take responsibility for our weight, actions, and everything else that we are and do. crabby thanks for your humor on the subject.

  12. I agree with this study in that who you hang around with affects your weight. Picking your friends based on that is totally ridiculous, though!

    I have two example of how this study is true. I will piggy back on Lisa's pregnancy theory. When I was pregnant my husband gained about 25 pounds. We BOTH ate ice cream every day. Not such a great choice for him! Haha!

    On the other side of the coin, I have a thin, health concious friend that I always make better choices when I eat with her. This weekend she came to visit and I figure I lost a couple of pounds which is the norm when I visit her. (Maybe I should just move in for a while!)

    As I was typing this I also thought of how I eat when my father is around. He is unhappy with my weight. He is thin, but apparently accomplishes it with portion control, not necessarily healthy choices. I eat whatever I feel like when I am with him, and would probably gain weight if I lived with him.

    Hmm. Interesting!

  13. Who steps on the scale with their socks on?

    I spent part of high school at a boarding school away from home and I must've gained 18 or so pounds in the first couple of months. All of my chums did too though so it just felt relative. Plus, we were all out in the middle of nowhere with barely any media access. What's thin when everyone around you gets bigger too? It wasn't til I went home for the holidays that I realized I had (ahem) packed on a few.

    As for this:
    "If you are trying to lose or control your weight, pick your friends carefully. You may not want to be around people who are gaining weight or who are too heavy." Well, that's just sad.

    And I can't tell if I want to go barf after seeing the "Baconator" or go to Wendy's for lunch.

  14. Eating has always been a social activity for humans, and people have always preferred to make friends with those who have similar interests.

    So if your interests gravitate toward cooking and knitting, you'll make friends with people who spend a lot of time sitting, and who will share their brownie recipes with you.

    If your big interest is running marathons, your friends will be inspiring you with stories of their weekly run mileage and what fruit you should eat to get maximum antioxidants.

    In either scenario, you'll end up being more like your friends than not. So while this study is nice, it doesn't say much that a person can't figure out from just living life.

    The real question I have is how I can get a large grant to study something similarly intuitive, like how workers who leave comments on blogs during work hours often end up taking work home at the end of the day. ;-)

  15. Kery,
    Diet Blog has it too--I guess this study just caught everyone's eye.

    And as to the suggestion we ditch our overweight friends, I'm with you: barf party!

    Dr. J, you crack me up. (And if I tried to meditate while running I'd probably run smack into trees, but your meditation seems to be of the powerful sort that allows you to fell them with only your mind!). And yeah, to solve that old question you would have had to have not been there in the first place, in which case...oh hell, never mind.

    Hi Lisa,
    That's interesting to see the phenomenon play out in pregnancy too. And you're right, let's hope people aren't dumb enough to try to ditch their pregnant friends too, yikes.

    Hi miss Martha!
    I agree, everyone should take responsibility for their own eating habits. And actually, the heavy people I know often tend to eat less than I do, at least when we go out to eat. They're actually a good influence on me.

    Wow, interesting observations. I think making this stuff conscious, rather than unconscious, is half the battle.

    And with your knee & mobility problems of late, it must be extra hard to balance the calories/exercise. I'd think the last thing you'd need is someone eating unhealthy food around you at the same time they're disapproving of your weight. Will be interesting see if your patterns around Dad might change at all now that you're conscious of them.

    Back in a bit...

  16. Katieo,
    The socks--you're right! And I had a similar experience when I went off to college--gained a bunch of weight because I did what everyone else was doing and feasted on junk food. You really do look to what others are doing I think. And your Baconator comment totally had me laughing--I have that same reaction sometimes to absurd fast food monstrosities--half appalled, and half tempted.

    Bunnygirl, I agree it all sounds like common sense--but I was surprised at how strong the influence was. I have this illusion that I'm my own person, but who knows how much I'm being influenced by my friends? And I'm totally convinced you could get a grant for that study--made me laugh but its so true.

    And to all: Will be out for much of the rest of the day but will be checking back this evening. May not respond to everything but as usual, will totally enjoy reading all that you might have to say!

  17. Not that I'm neurotic or anything - but do any of you think Crabby did a runner as she saw me approaching her blog? I don't have any socially contagious diseases. Honest!

  18. Crabby, having not quite left the building yet...

    Sniff sniff... is that the smell of cream-filled apple donuts? Must check back. Ah, look what Dawn left unguarded! Snarf snarf snarf... yum.

    Now must really go attend to errands!

  19. I just posted a related post on my new blog! http://steppin-up.blogspot.com (my name links to my other blog - any ideas how to post with a name linked to my new blog?)

    I agree with what a lot of you have said - friends can impact what you eat, but to choose your friends based on that is just ridiculous.

    I've noticed this happen to me - I rarely eat fast food, but when I started kickball, every week after the game, I would go for pizza with friends because that's where they wanted to go (and it was cheap). I've also noticed that if my friends are eating healthy, it's easier for me, especially if there's a dinner party of some kind.

    But I'm not going to stop associating with people because they're larger, whether or not they make good food choices. Seriously. I'm not friends with them because of what they look like or what they eat, I'm friends with them because they're cool people and I like hanging out with them.

  20. Pick your friends carefully? Ew. That's all I have to say.

    Well, that and go Ags! Or mustangs, or cows, or whatever the heck we were supposed to be.

  21. It's an interesting study, but it's still not clear to me how the fatty field extends to people who are hundreds of miles away. When I chat with people who are far away, I don't usually discuss eating or weight or exercise(except when I talk to my mother, but that's a different story) and I've been surprised in the past when I see someone in person and realize their size has changed. Maybe it's because people with an active lifestyle are more likely to be friends with others who have an active lifestyle?

    Anyway, it makes me kind of sick to my stomach when I read the "don't be friends with fat people" spin I've seen in the news. I'm by far the largest in my social group and there have been times when we are out that I'm self-conscious about my weight. The last thing I need is to feel like I'm contaminating them somehow.

  22. Actually looking at the study, it really surprised me that a "mutual friend" had a much greater impact that a spouse (see Figure 4), since spouses presumably spend more time eating and socializing together (or maybe that's a bad assumption). Anyway, something that doesn't seem to be making the news reports is that the effect is much greater between male friends than female friends. From the report:

    "Among friends of the same sex, a man had a 100% (95% CI, 26 to 197) increase in the chance of becoming obese if his male friend became obese, whereas the female-to-female spread of obesity was not significant (38% increased chance; 95% CI, –39 to 161)."

    It seems like bad reporting to focus on the overall percentage of participants who are affected when there is such a big discrepancy between the effect on men and women.

  23. "use your brain" - why would we want to do that? That would MAKE SENSE, Crabby! ;)

  24. So, my dear crabby friend are you trying to tell me that I am supposed to make healthy eating choices when I am dining with my dad even those he is ordering eggs bacon and sausage and just looked sideways at me because I am thicker than the last time he saw me!?!?! Argh!!!

    This is so totally not fair!!!! wwaaaahhhh!

  25. Hi Crabby!
    What a lucky chance finding you thru Blogs by Women Bloggers! Your blog is terrific -- I'll be back to read more. This is so up my fat alley!
    Great blog!

  26. Hi Everybody--sorry to be Slacky on comments tonight. And what a night I picked to go AWOL.

    Great comments--and Lethological Reader has a new blog! Peggy has a great analysis of the research including the bit about gender influence on the friendship factor that I totally missed; Sara, a star blogger from Marks Daily Apple and Healthbolt shows up to say hi; Norabarnacle reveals she doesn't know who her University Mascot is (I had to google mine, actually, 'cause I couldn't remember it and what the hell is a Triton anyway?); Holly has a Painful yet Amusing Epiphany involving bacon and eggs, and we welcome great new reader Lara into the craziness that is Cranky Fitness! Lara seems to have a formidable feline support system over at her blog, so hopefully she doesn't scare too easily and won't run away when she discovers what a bunch of loons we are sometimes.

    Night all!

  27. Hmm, I don't know about the the shorter people needing smaller portions or not. I really was naturally slim (much the way my very tall brother still is) and then I had some major weight issues because of the meds I was on for my mental illness. So I went from being a healthy 102 to a very obese 210 in two years or so (most of it being put on within the first year). And that's really what screwed things up. I had to have corrrective jaw surgery last October and was wired shut for a month and my jaw didn't heal right so my food intake decreased and I stopped taking all my medications because I had to have liquified versions that were making me puke... So I lost 60 pounds. And now it's all stopped and stuck here.

    I really wish I did know, because I have a very big appetite. Then again during some of my skinny time I was bulimic (I was big into ballet at the time) so binging became like a norm for me. I really don't know.

    The skinny friend I shared the article with (as mentioned in my first comment) is not much taller than I am. But then I guess she eats as healthy as she can with a busy job (as a pastor) and wit two young sons. Somehow she keeps it off (I hope that means she's actually finding time to eat?).

    So it's a mystery but if you do further this genius theory and some researcher picks up on... they can use me ffor their experiments since now I'm interested and need to lose some weight. My body was made to be very small. I have very small feet and hands and teeth and even small veins. I suppose that only offsets my much too big middle section even more. I do think the weight thing is even harder when you're really short. But anyway, I should be sleeping...

  28. I have no friends.

    I hang with Sadie, who Karen refers to as my sister, although we are not blood related. Sadie is quite tall and thin, like a supermodel. Furthermore, like many in that industry, she is also bulimic and barfs all over the house. I'm not exactly sure why she does this. It's not like she wears clothes and has to fit into a size two cotail dress. She has no friends to impress, either.

    I would describe myself as volumptuous and short. In my experience, Sadie's behavior does not effect me and my sense of body image or worth. I am fabulous and brilliant. Sadie is a dullard who happens to be thin. End of story.

    I discussed this with Karen and she saw more legitimacy for humans. According to her, if your friends are drinking and eating and having a good time on the town, you are probably right there with them. If your friends are at the gym using the elliptical machine, you probably are as well.

    Evidently you people put a lot of stock in your buddies. Must be nice to be allowed out of the house to pick them!


  29. Thanks Meg! And yikes, jaw surgery sounds like an unpleasant way to lose weight.

    Penelope, we truly needed a feline perspective here. As usual, cats show themselves to be much more independent and admirable creatures than us sheep-like humans who are so easily influenced by others.

  30. I don't know about my friends making me fat, but my family certainly doesn't help my healthy eating strategy any. My son only eats potatoes, corn and beef. My husband has the metabolism of the Olympic swimmer he used to be, so sugar is no enemy to him and my daughter is 10 with a 10-year-old's metabolism. My struggle is that I usually make them dinner and then I make my own.

    At least if I go out to eat with my friends, we all order different stuff and it isn't such a big deal.

  31. Hi SmartCookie,
    Boy, I'd struggle with that too. I think trying to eat appropriately for my metabolism would make me feel completely martyred if I had to watch every one else eating the fun stuff all the time.

  32. I have company almost every weekend and consistenly gain weight over those two day, and lose it through the week when I'm on my own. It's absolutely the company I keep...

    and the food choices I make...

    and the lazier walks...

    and the lack of willpower...


    ok, maybe it's me. :)

  33. Hilary,
    Very funny! (And I say go ahead and blame the friends anyway).

    Great blog you have there over at The Smitten Image--thanks so much for stopping by!

  34. Sure..why don't we just round up all the "fat" kids and adults and isolate them even more by locking them up so we don't "catch it" They have a hard enough time with society accepting them and usually don't have more than a couple friends any way and are ignored a lot even by adults..so who would miss them? /rolls her eyes

  35. Anonymous,
    I know, isn't it stupid? Hard to believe "experts" would tell people to shun their overweight friends.

  36. I know this is a few days old, but I haven't had my fill of ranting about the "don't be friend with fat people" spin yet. Sometimes I wonder if the "expert" doctors who come up with interpretations like that deliberately say stupid things just so they'll get quoted in the newspaper. More stigma around body weight isn't going to help anyone's weight. Interesting study, though, as far as making creative use of the Framingham data.

  37. ^ Oops. I was going for "More stigma around body weight isn't going to help anyone's health" and missed.

  38. Hi JaneDoe4,
    I think you may be on to something--perhaps these stupid expert quotes are just to make people mad and get more attention? (Like the woman who said microwave ovens cause obesity?) Because why else would you say something so offensive and dumb?

    And your observation about stigma actually made sense both ways.

    And one more thing (because you sound sort of science-y the way you talk about Framingham), have you noticed that it seems like a lot more "studies" these days seem to be reviews of data from previous studies? Don't know if the computer programs are getting more sophisticated or if they're just running out of money to find fresh populations.

    Anyway, thanks so much for stopping by!


    Just think, in 20 years this will have become part of standard "knowledge". To refute this, school children will have to watch a video where the fat high school kid tells another kid "You can't catch fat from sitting next to me or drinking my chocolate milk!"

    You know, like the AIDS movie everyone had to watch in school? You know? Huh? Oh. No, maybe it was just my school. Nebermind.


Thanks for commenting, Cranky Fitness readers are the BEST!

Subscribe to comments via RSS

(Note: Older Comment Threads Are Moderated)