Breaking down BMI

When you have your first prenatal appointment, there are certain lifestyle changes your provider will recommend – stop drinking, take a prenatal vitamin, and maybe, for those in bigger bodies, start to track your weight gain.

But what if you found out that BMI is not a useful indicator of your health? BMI is actually a deeply flawed calculation that was only intended to be used for populations, not for individuals.

Let’s break down the fraught history behind BMI.

BMI: The backstory

BMI (first called the Quetelet Index) was invented by a Belgian mathematician (you read that right, not a doctor) named Lambert Adolphe Jacques Quetelet in the early 19th century. He set out to find the “average man” by studying the height and weight of (mostly) European men. His work excluded women and people of color. 

BMI, a calculation of weight (in kilograms) divided by height in (meters squared), was later picked up by health insurers and medical providers in the U.S. They used various BMI categories (underweight, normal weight, overweight, obese, and morbidly obese) to determine insurability and individual health. 

Is this starting to raise some red flags for you?

OK, but does it work?

The short answer is no, it does not work and there are a few reasons why.

1. BMI was originally created to indicate population health, not to determine individual health.

Quetelet was a statistician. His intention was to collect large amounts of data to uncover population-level trends, not to assess an individual’s health or risk factors. 

2. These categories are problematic for individuals who were left out of the original studies

Given the fact that so many groups were excluded from the development of BMI in the first place, it doesn’t make much sense to apply it to them retrospectively. Further, BMI suggests that there is an ideal height/weight ratio. This is simply not true.

3. BMI equates muscle, fat, and bone

The body is made up of (among other things): bones, muscles, and fat. BMI groups all these categories together into one, treating bone, muscle, and fat the same. Not only that, but which out of these three parts of the body weighs the most? Bone. The least? Fat.

So is there a better way to calculate health?

There are alternative calculations of health informed by weight, but the issue at play here goes far beyond the biased history of BMI or its misguided application to individuals, because even weight itself is not a strong indicator of health. Research has shown that simply changing one’s body weight is not a reliable measure of improvement in one’s health. 

If you’re looking to feel stronger and healthier, there are things you can do, like starting a health promoting behavior. 

Here are a few examples of health promoting behaviors

  • Setting a goal to drink more water
  • Figuring out what type of exercise you enjoy and doing it consistently
  • Finding a mindfulness practice that helps you tune into your inner needs
  • Intuitive eating: listening to your body’s requests for nourishing food

Setting goals like these – that are based on how you feel, how your body functions, and what you personally need to be living in a healthier body – is more reliably associated with improvement in overall health. 

Providers that rely too heavily on BMI might be missing the whole picture of your health. If you’re concerned that your provider isn’t understanding the whole picture of your health, seek out a HAES (Health At Every Size) aligned healthcare provider. There are therapists, body image coaches, doctors, nurses, and dietitians who are all trained in HEAS. You deserve to feel seen and cared for by your provider, regardless of your BMI or the size of your body. 

Reviewed by the Ovia Health Clinical Team

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