Why BMI is Bullshit

Oh, the magic “BMI 19.”

“Get to a BMI 19 and you’ll be healthy,” they tell us.

Bullshit. Utter crap. Hear me out…

Body Mass Index (BMI) is a very basic, and arguably erroneous, way to estimate the amount of fat that a person has on their body based on their height and weight.

Even the bloke who invented BMI (Adolphe Quetelet who published his “Quetelet Index” in 1832) said that it should not be used as a measure of fat on a person’s body. It is nonsensical in a scientific sense, as it makes no allowance for the relative proportions of a person’s muscle, bone, and fat. And guess who is responsible for turning the Quetelet Index into “Body Mass Index?” None other than our old pal Ancel Keys, whom I have a love-hate relationship with, as although Keys is responsible for the misguided war on fat (for which I will always be cross with him), he also did the Minnesota Starvation Study.

Okay, back to the present. Ironically, although the CDC uses BMI as a measure of health, the CDC’s own data show that BMI measures are inaccurate at determining … well, just about anything really. You can be the exact same height and BMI as someone else and have very different bodies. Oh, and not to mention that very same data shows that nearly half of the people classified as “obese” by the BMI standard were perfectly metabolically healthy, actually. That’s because the human body is an organism not a fucking math equation.

It’s all rather embarrassing now really. Most medical practitioners seem to know deep down that BMI isn’t really a reliable indication of health, yet they still pull out that dumb chart and trace lines along it. It’s like a fly that won’t go away no matter how many times you bang your head against the wall.

The reason I get riled up about this is because something that absolutely should not be used as a measure of health is the most commonly bloody used measure of health for people in recovery from life-threatening restrictive eating disorders. Again and again and again. It’s like using leeches to treat a fever — might have seemed like a good idea before we knew better, but now we know better. I imagine that if your doctor started trying to put leeches on you every time you got a fever you’d run a mile. (I actually don’t know very much at all about leech therapy, so I shouldn’t judge. Apologies to any leeches who are actually wonderful healers.)

It’s hard enough to convince people with eating disorders that they are in a state of malnutrition as it is. The last thing you need is a stupid chart on the doctors office wall telling you that you are healthy when your mental state is a shit show because your body is in malnutrition and one part of your brain is desperately telling you to eat and the other part is screaming at you not to. Oh, how wonderful that a little chart on the wall that was thought up by someone a couple centuries ago on a whim knows more about your body than your actual body does. Never mind that your hair is falling out. Never mind that you think about food the whole time. Never mind that you are in a constant state of anxiety. Never mind that your heart rate is still dangerously slow. No, the chart says you are okay, so you must be okay.

Bollocks. Utter bollocks.

In the video below I explain why a BMI of 19 does not equal nutritional rehabilitation for every person who has a restrictive eating disorder. I don’t even yell. But I feel like yelling about this all the time because it is so ludicrously stupid that anyone would ever have thought that was the case. Let alone that many people still do think that it is the case — people with degrees at that! I mean, I didn’t even go to around 80 percent of my lectures at university, yet even I can look at a standard distribution graph and see the problem with recommending that everyone should be at a weight that is below that of the general population.

It’s like treating anorexia with anorexia. Here, put on some weight, but let’s try and control how much weight you put on and when, because wouldn’t it be the end of the world if you actually put on enough weight to be anything other than underweight … 

So for those of you who don’t like to watch videos, here is my explanation:

BMI ranges (underweight, healthy, overweight etc) are based on a bell curve of the population. So, even if we were to use BMI as a indicator of nutritional rehabilitation (which we should not) why the heck are we being told that everyone is “healthy” at a BMI of 19, when a BMI of 19 is below the average for the human population? BMI 19 has just got its foot in the door of the “healthy” range. It hasn’t even taken its coat off yet. It could visit the loo and come out underweight.

When we assume that BMI 19 is “recovered,” we are assuming that every person in recovery would be a person with a naturally low bodyweight once recovered. There’s a nice chuck of misinformation that doesn’t recognize that eating disorders affect people in all sizes of body.

As I explained in last weeks post, if your natural, unsuppressed bodyweight is a BMI of 26, and you are only nutritionally rehabilitated to a BMI of 23, then you are suppressing your bodyweight and you are underweight. If you stopped at a BMI of 19, then you are very underweight!

Mental state is what indicates your nutritional rehabilitation status. Not your weight. And not some BMI pie in the sky.

Do you know what makes me really proud of people through? The emails I get from people in recovery telling me that although their doctor has told them that they are recovered, they know that they are not, and that they are going to push on challenging restriction and allow that higher, unsuppressed bodyweight and see what happens. Because they know that they know better. They know that they are not “okay” and they know that they can’t settle for a half life. And that is amazing, because everyone deserves full recovery.

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What do you think?

  1. Thank You Tabitha! I do not bug you anymore. I have started to do major changes in my life. Lower level-movements are most difficult to eliminate, but I do my best, I have to. I do know, that I am not healty yet, far from it. Say doctors whatever about graphs. “I don`t want to just stay alive, I want to LIVE”

  2. Hallelujah to you for posting this. BMI is bullshit to say the least and it is very dangerous to use as the only tool measuring one’s overall health. The human body is so complex and no one body is like another. It is especially BS when it comes to eating disorder recovery. I posted this in the past but I will say it again that my daughter needed to gain weight way above the so called suggested BMI. There were times that I was asked to reduce her caloric intake (for fear of what I am not sure) but I found that as soon as I did that–the eating disorder got stronger and wanted to restrict even more. So, I had to keep her intake higher -not just for her body but also for her mind.
    Hospital treatment programs do use BMI to facilitate eating disorder recovery but I feel that we do a huge disservice to the patient when we consider this to be the only measuring tool. for health.

  3. I absolutely HATE it when doctors recommend people with Anorexia to stop at a certain weight. I had literally only gained 3-4 pounds in my recovery when my dietitian told me to stop- and I had lost over 40 pounds to begin with! Plus I was still growing, so I should have gained something more like 45-50 pounds! I am still seething at that woman. She set me back in recovery for at least 2 months because she convinced me that a BMI of 17.5 was healthy, because ‘you’re only a teenager’! And, to think, she told me herself that she ‘used to have anorexia’!

    If I hadn’t discovered your blog, Tabitha, I doubt I’d be any further along in recovery than when I weighed a BMI of 17.5 and was eating barely 1,600 calories a day. I cannot thank you enough for all that you’ve done. You allowed me to recover, you gave me that little shove I needed to push me along in my recovery. I can only say ‘thank you’. 🙂

  4. I’m crying, just thank you so much. I’m large and muscular- a powerful tall person and to be told over and over to lose weight till I’m 145lbs…it almost killed me. I went to the doctor and they told me I’m still too fat and “What are we going to do about your weight problem”.

    Hair was gone from my head, had a furry chin a dwarven princess would be proud of, nails split down to my cuticles, tongue so dry I couldn’t taste anything- but no, couldn’t have anorexia because my BMI was too high. I had lost 80lbs in five months, but they didn’t care. The doctor told me ‘keep doing whatever you’re doing because it’s working’.

    On what planet was this working- because it wasn’t Earth..

    I’m recovering now, I’m eating and scared but I’m going to make it. I’m going to make it, and I’ll be strong. Thank you so, so, SO much for writing this. Thank you.

  5. Hi Tabitha,
    I am a 40 year old married mother of two boys, aged 9 and 11. I recently stopped working to devote more time to recovery. I have been anorexic
    (off and on) for the past 30 years. I’ve been seeing a therapist since this past July, and have chosen to go “medication-free’. I am currently in the
    re-feeding stage of recovery, and have gained 4 pounds. I am not severely underweight, so my medical doctor advised me to gain another 10 pounds. I could go on for days with how much you are helping me, but will simply say the following: your wisdom is SAVING MY LIFE.
    I listen to your podcasts everyday. I am forever grateful to you! _Tina

  6. This. So much this! I’m at a point where I can finally say I’m extremely fortunate that my treatment team thinks BMI is shit. I never made it under 19. That was, of course, ED’s goal. My body on the other hand gave out at 19.22. I’m not being overly dramatic when I say I think my goal weight would’ve killed me. I read so many horror stories of people that have been kicked out of treatment once they hit 19 because the insurance companies think that’s what recovered is. And I’ve talked to people who clearly are still deeply entrenched in their eating disorder but think they’re recovered because they’re not clinically underweight. It took me ages to realize that my eating disorder was serious enough to warrant treatment (and this didn’t happen until quite a ways in), and if my team went by BMI I wouldn’t be getting the help that I desperately need.

  7. Im currently in a tricky spot. I went from BMI 42 to BMI 17.5 with my eating disorder. I put myself into recovery after family made comments on my ‘too skinny’ body and talking to my GP who also commented that my weight was ‘getting too low and maybe you should stop counting calories?’ (despite my GO being supportive of my initial weight loss..), and regained to about BMI 24 (EXTREME hunger eating set in after force feeding myself for a couple of weeks, I just couldn’t stop myself when it hit me) over about 6 months before I completely freaked out (because I was ‘getting fat again’ and therefore obviously eating too much) and relapsed. It took my anxiety therapist to tell my GP that I needed to be referred to the eating disorder clinic. He did that, I was diagnosed with Atypical Anorexia Nervosa.

    Unfortunately I’ve been on a waiting list after the initial assessment sessions where I was diagnosed. I am losing again and am BMI 21ish. I’m so hungry, I am so hungry, but I do not feel ‘sick enough’ to recover. I do not even feel like I am eating little enough to warrant being so hungry, and to daydream about eating as much food as I do daydream about. But at the same time, I am certainly not as hungry as I was when i was 17.5… so that also makes me think that I’m NOT actually hungry, I’m just greedy and looking to make myself fat. Looking for permission to be greedy and fat. And I am a bad person for that. I don’t think fat is bad in general, but I feel I personally do not deserve to be fat – I’m not good enough a person to let myself. I don’t know how else to put that into words.

    If I eat, as much as I wish, I will get fat again and I am absolutely terrified of that. But.. whats the point of eating more, if I am still hungry? I feel like… say they give me a meal plan that might still leave me hungry. If I’m going to be hungry anyway, I may as well carry on restricting, and at least eventually be thin to show for my hunger? What’s the point of eating more, getting fatter, but still being this hungry and feeling so unwell?

    I have no idea what my new therapist will say, I will be seeing them for the first time next week.

    I honestly just want someone to help me make everything okay, and make all this go away… but I have no idea what it all ‘going away’ looks like.