Fundamentals: Why BMI is BS

Welcome to the first post in the Fundamentals series, and I guess the first real post of Can I Have Another Snack? I wanted to create a library of posts that covered essential topics in the anti-diet parenting cannon. If we’re going to be hanging out here loads (which we are, right?), I think it’s important that we have a shared understanding and common language for discussing foundational topics. I’m calling this series Fundamentals. And you can find this column by clicking the tab at the top of my Substack page.

Let’s start with the Body Mass Index, or BMI - something that we have all felt personally attacked by, and most likely, have a pretty complex relationship with.

For decades, the BMI has been used as the universal standard for measuring ‘health’ (another complex topic I’ll write about soon). It’s pretty much a given that whenever you visit your doctor or go for any kind of health check-up, they will ask you to step on the scale, and ask you how tall you are. These two metrics are then plugged into an equation - weight in kgs divided by height in metres^2. This generates a number that then goes onto determine your ‘health’ status, the medical options that are available to you, and - I cannot stress this bit enough - how much of an asshole your doctor is likely to be to you.

So what exactly is BMI measuring? Where did it come from? Why is it so ubiquitous? And why is it total bullshit on every conceivable level?

Let’s start with some history. You might be tempted to think that the BMI was created by a physician, or at the very least, a biomedical researcher. Maybe an epidemiologist or someone with a background in public health. Any of those professions might make some kinda sense. But nope, it was a Math Guy. Don’t get me wrong Math Guys are great (I think I might be married to one?). But they frankly don’t know shit about shit (outside of numbers, duh).

OK so our Math Guy is called Lambert Adolphe Jacques Quetelet - a statistician and astronomer. Circa 1835 Ol’ Lambo set out on a quest to quantify the characteristics of what he called l’homme moyen. The average man. He measured different physical attributes of conscripted Scottish Highlanders (trust me, a very average dude), such as chest size. He then, in a completely illogical lateral move, attempted to quantify ‘moral’ attributes, such as suicide, crime, madness, and most bizarrely of all, aptitude at poetry.

Starting from this super solid basis, he then went on to measure the weights and heights of the aforementioned average Scottish dude, and threw some French guys in the mix, because why not? What he found, unsurprisingly, was a normal distribution, which, when plotted on a chart, takes the form of a symmetrical bell shape. Just like a bell, there is a cluster of weights around the centre indicating that is the average (mean) weight in that sample. And there are people who lie either side of the average weight, who fall somewhere along the domed part of the bell, indicating that there are people whose weight is simply higher or lower than the average.* So far, no big surprises - just good old-fashioned body diversity

*I ran this explanation past my Math Guy. It checks out.

But here’s the plot twist. Instead of labeling the ‘average’ weight as ‘average weight of a group of very average white bois’, Lambo called it the ‘ideal’ weight, and therefore anything above or below this ideal, became ‘undesirable’.

So let’s recap - a dude with questionable assumptions, made an equation based on a completely unrepresentative sample of young, white men, to capture the characteristics of that sample, which now gets used as a measure of individual health. For everyone. And also this highly sophisticated piece of medical technology is around 200 years old. Great start.

As we’ve discussed, Lambo was a mathematician. But his side-hustle was eugenics. Lambo is not a Good Guy. And his work became the basis of a lot of other Not Good Guys to justify systematic violence and dehumanisation of anyone who did not fit the ‘ideal’ that they had conveniently created in their own image. Essentially, anyone who is not a thin, white, hetero, cis-man.

BMI was a deliberate attempt to exclude and people of colour, especially Black people. From its inception, the game was rigged.

In Belly Of The Beast: The Politics of Anti-Fatness as Anti-Blackness, Da’Shaun Harrison breaks this down further:

‘From the moment white Europeans saw fat Africans, the science that followed was intended to always separate them from the rest. In this way, the BMI - created to maintain whiteness as superior - was always going to harm the Black fat and it is for this reason that Black people make up over half of the fat population and why Black people also have more “health risks” than their white counterparts.’

In the same time frame as Lambo was conceiving l’homme moyen, his contemporaries in the scientific community were contriving hierarchies of humans based on their alleged ‘civility’ or how ‘evolved’ they were; a ‘cataloging’ of humans which has contributed to the racialisation of groups and served as the rationale and justification for eugenics. It provided a ‘scientific’ basis for the subjugation of people of colour, disabled people, and anyone else who ‘deviated’ from conservative and puritanical Christian values. And, as you’ve probably guessed by now, the folks responsible for creating these categories were predominantly white men, of northern European descent - including Charles Darwin). These guys put themselves on the top rung of the ‘Ladder of Cultural Evolution’ - a theory devised by ringleader Lewis Henry Morgan that was accepted as scientific at the time. It posited that there was ‘a natural hierarchy between cultures that supported racial prejudice and subjugation of the perceived lesser peoples’. According to Morgan there were three distinct categories of human. Him and his mates belonged to the ‘civilised’ group. People who came from countries that were considered ‘semi-civilised’ were categorised as ‘barbaric’. The last group, ‘savages’ included Africans and other indigenous peoples, who, as Harrison points out, were often heavier than their European counterparts. The classification of these peoples as ‘savage’ codified fatness as primitive and ‘uncivilized’.