I wanted to email my doctor about this. There doesn’t seem to be a way to do that, so it’s going on my blog instead.
I went into my yearly checkup1 with more paperwork than usual. The past year included a strange medical episode that turned out to be nothing, which meant I arrived with a full panel of blood work and a recent cardiologist visit, testing included.
The blood work was perfect. Blood pressure, perfect. The cardiologist rated my fitness as “good.”
My doctor looked at all of that and told me I might want to consider losing some weight. My BMI is 30.6, he said. A little high.
Nothing attached to it. No specific concern, no plan. Just the number.
I was expecting it. He gave me the same advice at my last checkup, when I weighed 6kg less. I gave up on losing weight for the sake of losing weight a long time ago and I haven’t stepped on a scale in years.
So this time I was ready to say something.
The interaction
I asked whether we were still doing BMI, like its obsolescence was a foregone conclusion.
He seemed genuinely surprised, and asked why we wouldn’t be. I said I thought we’d decided it was racist, sexist, and not very useful.
The “racist” part is what got him. As far as I could tell, he didn’t think I was serious.
I shrugged. He explained that BMI is still required for certain things, filling out forms related to surgery, that sort of thing. Then he offered Sylvester Stallone: a guy with five percent body fat is going to have a high BMI too. I asked whether we should be measuring body fat percentage instead.
That’s about where it ended. I’m going off memory, so don’t hold him to any of that wording.
I regret it a bit
I was medium rude.
Worse, I wasn’t prepared to back up my own scuttlebutt. I walked in with a strong opinion assembled entirely out of things I’d absorbed somewhere, which is a habit of mine. I synthesize facts as true based on vibes alone2.
So I went and read a bunch of medical journal articles, mostly to find out whether I’d been talking out of my ass.
Partly, it turns out.
“Not very useful”: confirmed
The best thing I found was Obesity in adults: a clinical practice guideline (pdf) published by CMAJ. It’s written for Canadian primary care providers.
Although BMI is widely used to assess and classify obesity (adiposity), it is not an accurate tool for identifying adiposity-related complications.
The guideline also spends real time on weight bias. The recommendations for managing obesity in adults open with several points telling the health care professional to examine their own biases. Not somewhere in the middle. First!
To be clear about what this document is: it treats obesity as a chronic disease and it recommends managing it. I’m not citing it to argue that weight doesn’t matter, because I don’t think that. What it backs up is the narrower thing I was getting at in the room, which is that BMI can’t tell you whether mine is a problem.
“Racist”: kinda, yeah
Small disclaimer upfront: I don’t think my doctor is racist, and none of this is meant to suggest it.
In 2023 the American Medical Association adopted a new policy on the use of BMI3. The policy itself doesn’t use the word racist. It says BMI is an imperfect measure that shouldn’t be used on its own, and it says why:
BMI cutoffs are based primarily on data collected from previous generations of non-Hispanic white populations and does not consider a person’s gender or ethnicity.
That’s a real limitation, and it has consequences. Different populations carry fat differently and develop disease at different BMIs.
The word itself turns up in the AMA’s own journal. In July 2023 the AMA Journal of Ethics published Sabrina Strings’ How the Use of BMI Fetishizes White Embodiment and Racializes Fat Phobia.
So the vibe I walked in with wasn’t coming from nowhere. But I hadn’t read any of this ahead of time, which is sloppy and sort of an immature way to walk into a meeting with another adult who is a professional in this field.
That article is where the history gets ugly. And it’s the type of ugly history progressive society has been distancing itself from, more and more every year. To the point where we actively replace bad ideas and conventions with new ones4.
Where the number came from
Adolphe Quetelet worked out the formula that would become BMI in the 19th century off a sample of 24 men and 24 women. He was a statistician describing population averages. He wasn’t building a clinical tool for individuals.
Strings’ argument is that fat phobia was racialized well before it was ever medicalized.
Fear of fatness did not begin as a medical concern. In fact, it took off in the mid-18th century. At that time, several race scientists began arguing that being “too fat” was bad specifically because it had been linked to women of color.
Ancel Keys is the one who changed that. He spent about twenty years arguing that the accepted measure of the day, weight against height, was no good. In 1972 he published a study of 7,424 men across five countries concluding that Quetelet’s formula was the best of the available options, and he gave it the name we use now.
Strings’ account of Keys includes some things he allegedly said about fat people in front of friends that are hard to read as clinical judgment.
Keys…was interested in the question of fatness for reasons outside of health. Keys allegedly described obesity in the presence of his friends as “disgusting,” “a health hazard,” and “ethically repugnant.”
He also claimed that “very fat” people were “clumsy and prone to accidents,” although the evidence to support this claim, too, is lacking…Keys’ concerns about fatness were shot through with white aesthetic priorities.
If you’re even vaguely aware of the concept of eugenics, a measurement-based ideal should get an automatic 🚩 from you.
The history matters because it explains the shape of the thing. It was built to describe the average white European man of the 1830s. What it displaced was the life insurance industry’s ideal weight tables (based on the average policy holder at MetLife5 so also mainly white). It was only in the 1970s that BMI was handed to physicians as a description of everyone.
“Sexist”: not exactly
This one is indirect. From what I read, the ideas that led to BMI weren’t uniquely sexist for their time, which isn’t much of a defence.
And again, Quetelet’s 48 people were half women, for whatever that’s worth.
The AMA quote above mentions that the cutoffs don’t account for gender. So it’s there, it’s just not as pronounced as I thought.
What I actually wanted
I’m not owed a clean bill of health. If there’s a reason to think my weight is going to hurt me, I want to hear it, and I’ll take it seriously.
What I got was a number. It came without a reason, without a measurement that says anything about my health specifically, and without anything that I could do next. I brought great blood work, a cardiologist’s assessment and a fitness rating of “good” but 30.6 outranked all of it.
I got the sense that my doctor almost felt compelled to mention it. Like he couldn’t let me go without a recommendation. Which is what it is, I suppose.
- Which I schedule approximately every 3 years. ↩︎
- Honestly, I feel like I get it mostly right, most of the time. ↩︎
- Use of BMI alone is an imperfect clinical measure ↩︎
- The albeit less consequential, master vs main branch renaming of 2020 is the same sort of vibe in my mind. I like to support progressive vibes. ↩︎
- Yeah, the insurance company. ↩︎
