Intention vs. Reality: Why BMI Is Not Just a Tool

The new year is upon us. Last night, many people drank to excess, placed too much significance on where their lips were as the clock struck midnight, and woke up with their heads feeling like some epic battlefield of yore. Some of those same people, along with countless others, are at this moment shaking off the hangover and proceeding to attempt weight loss under such euphemisms as “getting healthy,” “getting fit,” “eating right,” or “taking better care of myself” (and overcrowding my gym for a month or so before they give up and go away until next year).

This will be all mine again soon enough.
This will be all mine again soon enough.

Yesterday, a piece was published on CSI’s page that addressed the concerns some have regarding BMI. While there are many issues with the way in which the piece addresses anti-BMI arguments, what stood out to me were some assertions about BMI and its uses that rang entirely false: namely, the notion that BMI is just a tool and is never used in unscientific, reductive ways by the medical community and world population at large.

The issue at hand is that BMI is not the simple calculating tool that some scientists and doctors think it is. BMI is often used as a weapon by which to shame, judge, and oversimplify people’s health and wellness.

suggesting that the measure [BMI] is a “demoralizing standard by which to judge a woman’s health” is bizarre: The BMI is not a “standard [of] health” (for men or women); it is a measure of adiposity (fatness). Though there is a strong positive correlation between excess weight and poor health, it is quite possible to be overweight (or even obese) and healthy. Thus the suggestion that the BMI is a measure of health is patently false.

The suggestion that BMI isn’t used to judge women’s (and men’s) health is what’s bizarre. Some health insurance companies charge people with higher BMIs more regardless of any other factors. A hospital in Texas precluded people from being hired based on BMI and no other measure of health, as does Weight Watchers. This is based on the belief that BMI is a sound single measure of health, one that clearly exists regardless of its falseness.

To use myself as an example, my health insurance is through Kaiser Permanente. Every time I go to the doctor, I’m “diagnosed” anew with obesity based on my BMI, as the printout I am handed at the end of my visit plainly states. This is true regardless of why I actually am making the doctor’s appointment in question.


It doesn’t matter if I’ve lost weight (I actually lost 10 lbs. between the visits documented above), begun eating better or exercising more, showed better numbers in terms of my pulse or blood pressure, or otherwise been told by my doctor that I’m doing well and should continue to do as I am: I am “diagnosed” with obesity every. single. time. and instructed to eat better and exercise more, even if I already had been. As per KP’s system, my health is very clearly being reduced to my BMI in relation to the BMI chart standards, no exceptions or circumstances considered.

Many of the BMI critics’ complaints are straw man arguments stemming from a fundamental misunderstanding of what the BMI is and what it claims to do. It is not a tool used by the patriarchic medical establishment for oppressing women, nor pressuring them to conform to impossible standards of beauty. It is instead a generally useful, accurate guide to helping average men and women determine their weight status

The misunderstanding here is not on the part of critics of BMI, but in those who defend BMI on the grounds that it is merely a guide or a tool. Most people understand that shaming others based merely on perceived fatness is a weak argument and so turn to BMI to gild their shaming with science. Check the comments on any article or picture involving a woman who doesn’t conform to the beauty norms of society: show a little tummy or arm fat (i.e. a lack of Photoshop) and suddenly, the entire world is convinced that your BMI is too high and you’re going to die of teh fatness because science. When body-shamers know that they can cite BMI as a medical fact, they can pretend that their offense at someone’s “rolls” or “jiggling” has nothing to do with aesthetic preference and/or social conditioning regarding attractiveness.


Laypeople judging perfect strangers online aside, my doctors in the past have been very good about reminding me that my BMI is too high in a way that was counterproductive. As a chubby teen highly aware of the fact that she was not at all thin, I had a doctor (whom I later fired when I realized that I could do so) who compared her weight and BMI to mine in her efforts to remind me that I was fat. In other words, a medical doctor used BMI to shame me — something that, ironically enough, fed the very depression that whetted my appetite for comforting sugar, fat, and salt.

To be clear, a doctor telling a patient that she ought to eat more fruits and vegetables and to exercise more is not body-shaming in and of itself. Indeed, if we were to glance at the statistics in terms of the average American’s diet and fitness levels, we could easily conclude that most doctors should be making such recommendations to most of their patients regardless of BMI. On the other hand, a doctor saying, “Look at me, I’m 45 and have had two children yet my BMI is just 25. You’re young; there’s no reason for your BMI to be so high” is certainly shaming; replace “low BMI” and “high BMI” with “skinny” and “fat” and it’s clear what is being said here.

It isn’t the fault of the tool itself that it used so crudely and wrongly, of course, but denying that such uses occur helps to bring no one around to its value, let alone encourage anyone to adopt healthier habits — and isn’t that the goal here? If tools are to be judged only on the intentions of their creators and/or their strict definitions, then the guillotine’s bloody reputation is unfair (it was only intended to kill real criminals and in a more humane way than by hanging), the Hitachi is a back-massager being cruelly misused by perverts worldwide, and Lifehacker, that well-known abuser of binder clips, shouldn’t exist.

Even as a simple tool, BMI isn’t cut-and-dried, set-in-stone medical science, especially with regards to assessing the health of a single person. As Dr. Steven Novella says in a comment on the very piece quoted in Bashing the BMI:

BMI is useful in the aggregate, but not applied to individuals, where other factors need to be considered, and other measures are far more accurate. […] We need more data to sort this out.

The discussion about and research into BMI and for what it is and isn’t useful, then, is far from over.

To deny that BMI is used in the way that it actually is in society is to ignore reality in favor of a hypothetical universe where nothing signifies anything other than what is in its stated definition. There is such a thing as connotation above and beyond denotation. In a culture where thinness is considered the epitome of beauty, health, and even moral character, where discrimination is rampant against the not-thin (especially women), BMI cannot so handily be divorced from its actual uses.

Heina Dadabhoy

Heina Dadabhoy [hee-na dad-uh-boy] spent her childhood as a practicing Muslim who never in her right mind would have believed that she would grow up to be an atheist feminist secular humanist, or, in other words, a Skepchick. She has been an active participant in atheist organizations and events in and around Orange County, CA since 2007. She is currently writing A Skeptic's Guide to Islam. You can follow her on Facebook, Twitter, or Google+.

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  1. Excellent article.

    How nice it would be for this to find it’s way into the mass media and get out to people.

    But no, the public wants to listen to what Dr. Oz has to say. Grrr.

  2. I was looking into additional life insurance (just to pay off the mortgage in case one of us dies) and disability (ditto, but for a case of morbidity instead) and to cover my husband for a mere $250,000 it was going to cost TEN TIMES what it would cost someone who DIDN’T have his BMI. They didn’t want to know ANY other of his health indicators. He has absurdly low cholesterol levels, always, without meds, he just sheds cholesterol. His blood pressure is consistently perfect and has always been. He exercises on a bike twice a day for about half an hour a time. He has NEVER smoked. He has maybe one glass of wine a year. His comparative risks for various conditions is very low. His family are long-lived. There’s no cancer or heart disease in his family. And all they cared about is that he’s overweight, and THAT justifies charging him ten times the amount someone with a BMI in the low 30s who smokes and drinks and never exercises with a family history of heart disease would be charged.

  3. I hate the BMI system, I love using Wii Fit but I hate that it uses BMI to harass me. I feel better, at a certain weight, because I’m usually eating right, and exercising more. So when I see that number and I feel good, I have to content with the Wii harassing me to gain weight. Of course that’s one of my complaints with the game (I love the activities, hate the harassment). I also used to hide behind BMI, my BMI always fell in the normal range when I checked it. So I was able to tell myself that I really didn’t have an eating disorder. I had to be “underweight” to have a problem. The fact that I just didn’t eat several meals a day, didn’t matter, I wasn’t “underweight.”

  4. BMI can’t even tell the difference between muscle and fat. LeBron freaking James is apparently in worse physical shape than I am.

  5. I thought BMI wasn’t even created by a doctor? From all I’ve heard about it, it’s a completely BS measure anyway, because it doesn’t take into account your body makeup. There are olympic athletes who are “obese” by the BMI scale, because they have so much muscle and the scale doesn’t take that into account at all. If it is a tool, it’s a pretty damn inaccurate one, and one that is in most ways unhelpful.

  6. As a public health nutrition student, I thought I would add in my opinion about the BMI. I personally like the BMI as a measure of how healthy someone’s body weight is. I find that when the media talks about body weight, there is no middle ground between dangerouly skinny and dangerously fat. The BMI offers a “healthy weight range” in between the the emotive “fat” and “skinny”. It is a shame that a hight BMI is used to make people feel ashamed of their weight. At least people with a BMI in the healthy range can be spared fat- or thin-bashing. While we would not see someone with a BMI of 23 on the catwalk (i.e. not meeting some people’s standards of “beauty”), they can at least know that they are not overweight. This is one advantage of BMI.

    Now to the nutrition stuff. BMI is a simple measure of weight compared to height. It has a limitation that people with a high muscle mass may be considered obese despite being very healthy. This does not apply to the >95% of the population that is not very muscly. For most people, BMI can give a good indication of health risk. It can be measured on a daily basis with inexpensive technology that is found in almost everyone’s homes. Other measures of health that are more accurate, such as a health checkup by a doctor, blood lipids, blood pressure, may give a more accurate measure of health, however at a much higher cost and inconvenience.

    On a side note, the BMI was developed by a mathematician and not “a doctor,” however is this relevant? It has been subsequently researched by and is used by many, many doctors.

    1. Do you honestly think fat people don’t know they are fat, and that they need a number to tell them that they are fat? A number that most people don’t even really understand and which gets misused constantly?

      ‘Cuz I’m thinkin’ most fat people know they are fat.

      “BMI can give a good indication of health risk.”

      it can give you an indication of sorts of health risk(s) … maybe. But GOOD? Perhaps combined with other factors, but on its own it’s really freakin’ useless for individuals. Fat people know they are fat. What one needs to know is whether they are healthy/can be healthier. And BMI can’t tell you that.

  7. “— something that, ironically enough, fed the very depression that whetted my appetite for comforting sugar, fat, and salt.”

    This is clearly an unbalanced diet. Alcohol is missing!

    (Seriously I relate all to well to this whole thing)

  8. The thing that bugs me about BMI is that you have to plug your height and weight into a calculation, get a number out and then compare that number to a chart. How, exactly, is this an improvement over the old height/weight charts that used the same data but didn’t require a calculator or computer?

  9. Heina > “The suggestion that BMI isn’t used to judge women’s (and men’s) health is what’s bizarre. Some health insurance companies charge people with higher BMIs more regardless of any other factors”

    That’s what happens when health care is handled by for-profit, insurance companies.

    Switching to a single-payer, public, national health-care system à la VA Health Care would make things a lot easier. But it’s as likely to happen in the near future as switching to the metric system :-/

  10. What I don’t like about the Wii Fit is that BMI is the primary indicator they give you — and hit you constantly with the obese/over-weight/etc label. I know I’m obese, I don’t need to be reminded of it every time I use it (heck, theoretically, that’s why I got it in the first place).

    My solution was to tell the Wii that I’m 7 feet tall. Then (a) my Mii is skinnier, and (b) the reported BMI is my weight/10. That makes it easier for me to pay attention to my weight, which is what I really cared about.

  11. Wouldn’t a chest to waist ratio be a more meaningful measurement?

    For example a man with a 44 inch chest and 32 inch waist wouldn’t be punished for having a large upper body compared to his waist. Of course what the cutoff number for a “good” ratio is would have to be determined and would be different depending on whether the person is male or female.

  12. Isn’t another problem with BMI that it would work poorly for the very tall or short?
    BMI divides the mass of the person by the *square* of the height, but if you have two people with different heights but everything in the same proportion the mass would go up as the *cube* of the height.
    Was the originator of BMI just ignorant or is there some obscure reason that might make using the square a valid thing to do?

  13. What a great article. The charts image! Seriously, everything gets attributed to obesity?! I’m just imagining how ridiculous that actually is. Sinus infection: obesity. Requesting birth control: obesity. It’s no wonder that some people are drawn to alternative medicine. Add to this the fact that some docs are simply jerks. (I once fired an OB for condescending to me about my infertility.)

    It seems to me that there is something inherent in the culture or the perceptions of power in (some/many?) doctor/patient interactions surrounding emotionally fraught topics like obesity, or childbirth, or vaccination that negatively impacts patient uptake and adherence. Focusing on BMI to the exclusion of other indicators of health is a good example of this. Every time I talk to someone about why they reject “Western medicine,” why they don’t vaccinate their kids or why they’re into whatever alternative SCAM they’re into, they always mention an unyielding doctor who either was condescending, or treated them badly, or “yelled at” them.

    So what would be a better way for doctors to talk to a patient about the positive health outcomes of lowering BMI (or weight, or whatever other measures)? Or to get people to vaccinate? Just to shift the framing slightly? If the goal is to improve people’s health, shaming is probably not the most effective approach.

    Also, how do doctors talk to each other about their own obesity? Do they? Does a doctor put the big red obesity stamp on the chart of a patient who is another medical doctor? Does the doctor status protect them from some of the societal bigotry? [/rambling]

    1. What I’d really like to see is doctors encouraging people to have healthy habits without framing it as a “you’re fat” issue. Really, people can be just as healthy with a few extra pounds as long as they’re eating better and moving more. Instead of dangling weight loss as if it were some kind of reward for healthier habits, perhaps recommend healthier habits as goals in themselves and if weight loss happens, so be it?

      Unlike what every person offering their expert anecdotal opinions on every thread about weight ever thinks, healthy habits don’t automatically lead to thinness (especially for women, as we generally lose weight faster than men do as well as hold ourselves up and/or are held up to higher standards of thinness than men are). It is very discouraging for the overweight to adopt healthy habits only to find that it take a lot of time and effort to lose weight.

      Come to think of it, this might be worth a post in and of itself.

      1. Yes, it certainly is worth a post in and on itself.
        I can’t wait to read it.
        I lost 80 kilos in the last year (I will spare you the anecdotes :-) ). Change of habits, endurance and a lot of patience, that’s what’s needed. There are no quick solutions.

  14. My biggest problems with BMI is that every time I see a doctor, they tell me my BMI means I’m morbidly obese like this is new information. I mean, no, really? I’m fat? I hadn’t noticed that I’d been shopping in the plus size section for the past decade! Silly me.

    Not to mention the fact that then they give me “helpful” suggestions like to cut out red meat or stop drinking soda, when I eat red meat about twice a year and pretty much only ever drink plain water. But I’m fat! Clearly that means I’m just lying about the fact that I’m mostly a vegetarian, hate soda, and rarely drink.

    I once actually kept a calorie log for a doctor, brought it in, and was promptly told I made the whole thing up, because obviously that wasn’t what I was actually eating. Because my BMI is 43, so clearly, all I eat is ding-dongs and potato chips.


    1. Yup. I had to fire a doctor because she kept telling me I needed to cut out soda.

      I told her, “I drink soda like twice a year, mostly I drink water or coffee.”

      She nodded, then kept going on about how much weight I’d lose if I quit drinking all that soda.

  15. A couple of months ago there was an excellent 3-part documentary “The men who made us fat” on BBC 2. The slender presenter/documentary maker had a perfectly healthy BMI. But when he had a scan it was revealed that he had 8 kilos of “inner” fat. His kidneys and liver were swimming in fat, which was cause for concern. Despite a perfect BMI he was in danger of getting the same problems that visibly obese people are likely to face. Diabetes, high blood pressure etc.
    BMI can be a relatively good indicator, but no more than that.

  16. The problem with BMI is it only works well in one direction, ie “if you are overweight, your BMI will be high”. It doesn’t work well in the opposite direction – if your BMI is high, it can be because of muscle mass. Also, I remember seeing many articles (notably one from io9) indicating that healthy habits are a much better path than losing weight. (ie if you eat vegetables, exercise regularly, etc, you’re better off than the average weight people who were “blessed with skinny genes” and never exercise or eat healthy)

    But as Michael Moore pointed out so aptly in a facebook status a few days ago, “It’s all a scam and it conspires to keep you miserable. If it says “low-fat” or “sugar-free” or “just 100 calories!” throw it out. Remember, one of the main tenets of capitalism is to have the consumer filled with fear, insecurity, envy and unhappiness so that we can spend, spend, spend our way out of it and, dammit, just feel better for a little while. But we don’t, do we? The path to happiness – and deep down, we all know this — is created by love, and being kind to oneself, sharing a sense of community with others, becoming a participant instead of a spectator, and being in motion.”

    The weight loss industry wouldn’t be the behemoth it is without all the fat shaming that happens now would it?

  17. I have an anecdote that may get at deeply-rooted biases. Around the time the Dr. Novella article published, I was attending a public lecture series at a teaching hospital. Before the obesity lecture, I interviewed a couple of 4th year medical students. One of the questions I asked was about the percentage of overweight/obesity among doctors vs. the general population, and if it’s lower among docs, why is that?

    I recall that their impressions were that overweight and particularly obesity is much lower among doctors, and they attributed this in part to education and having access to and deep understanding of the medical literature. They can cite statistics to their patients, but patients may or may not really understand in the way that doctors do.(I wonder if all patients are too ignorant to understand or if it’s just the fat ones.)

    They did think that doctors’ socioeconomic status contributes to access to a healthier diet, although I think the lecturer himself disagreed with this meme.

    The comment that really stuck with me, though went something like this, “There are hardly any overweight/obese docs here because doctors who choose to practice in Colorado are drawn here because they are athletic and active and prioritize outdoor activities like hiking and biking and skiing.” Interestingly, a few of the lecturers (from memory, roughly 25%) themselves were clearly overweight if not obese (I can’t tell by looking). Maybe they got a pass because they were men? Or because they were doctors?

    1. I hate them – I hate them all.

      Your anecdote confirms my experience that around 4th year they all change from reasonable human beings into jerks, almost overnight.

      1. Interesting theory. I thought it happened middle of third year, after the surgery rotation. ;)

  18. I have what might be considered a interesting perspective on this BMI Huha.
    I am a Soldier in the United States Army, into my first year of service. I work out 5 times a week in military PT. I have always passed every PT test, last time with a score of 164… That means I maxed my Sit ups 75 in 2 minutes… I performed 32 sit ups and ran a two mile in about 18:30. Not bad for an asthmatic 34 year old!
    But I’m Over Weight. Thankfully the Military has the good since to actually take out a tape measure and make a rudimentary estimation of my actual % body fat. Because of that and only because of that, I remain happily in the Military.
    But every time I see a doctor the first and last thing I hear about is how I need to diet. With out a care that my Percent Body fat is in range for military standards, with out a question as to my physical performance and often without addressing my true medical concerns.
    I’ve been on a diet since a year before I joined the Army, and will likely remain on a diet until the day I leave. I will never “make Weight”. I have no intention of making weight. When I was in my twenties I decided that I was going to work out and diet until I reached a “Healthy BMI”. I worked out for 2-4 hours every night, and 5 hours on Friday, watched every single calorie and after months, of work and obsession that bordered on disorder I reached my goal.
    I started to live a “normal life” at my Healthy weight and instantly gained back 10 lbs. And for what?
    I wasn’t prettier, I wasn’t healthier, I wasn’t that much stronger… I was lonely, obsessed, depressed, and utterly disappointed.
    This isn’t about health, or physical performance… this isn’t about strength or endurance… this isn’t even a measure of ascetic beauty. What is this thing measuring?
    This is just like every other box society tries to stuff it’s members into. The straight box, the gay box, the feminist box, the army box, the BMI box.

    I’m an human being, I don’t fit in a box.

  19. Great post. Not only is there good, large cohort studies that show little to no morbidity to being overweight or even mildly obese, but I know of a local hospital that will not let pregnant women over a certain BMI deliver there at all. BMI is used for scaremongering, and much of it is not evidence based.

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