Debunking Myths: BMI


Please note that this content may be triggering for you, especially when dealing or having dealt with an eating disorder. If so, you may want to skip this post 💕.

If you have read my post “Debunking Myths: Metabolism” you know that I have been recently upset about some new called “science” that has been floating around the internet as of late. There is still a lot of very outdated information floating around that has long been overhauled by science. Unfortunately, some of these outdated myths still hold fair and square… I have decided that as long as not enough people write about it, little will change. So, in our second post, we are covering the very prominent topic of BMI. Unfortunately, this is still a crucial tool used in today’s medical world.

What is the BMI?

The Body Mass Index puts in correlation a person’s weight in kilograms to their squared height in meters. Based on the number that provides the outcome, there are four categories a person can fall into. Underweight, healthy weight, overweight, and obese. This formula has been used for over 100 years and was originally derived by a Belgian astronomer in 1830. 

Man sitting in front of a screen with stock indices
Photo by Chris Liverani on Unsplash

Around 1900, the BMI became an indicator for life expectancy and was used to accumulate life insurance data. Tall people statistically had a lower death rate than short people with the same ratio due. This is due to the difference in height not being accounted for. It was also recognized that bone mass (whether someone was built in a broader way or more narrowly) was not considered. In order to mitigate these challenges, the height was squared so that the body mass distribution appeared to average itself out across its height.

Why is the BMI considered important?

The BMI, to this day, is a measure widely used as a risk indicator for the prevalence of health issues. It is used to calculate life insurance rates and largely determines public health policies. Despite its old age and flaws, it is an accepted metric. At the very least, my general practitioner has quoted it back to me multiple times.

Why is the BMI potentially outdated? 

There are several points that, unfortunately, this simple calculation does not take into account.

It is a Statistical Measurement

First off, let us not forget that the BMI is, primarily, a statistical measurement in order to create a uniform code when it comes to height vs. body mass. With that statistical measurement also comes that the mean (ca. 50%) are concentrated around a “healthy” weight area. By default, this means that ca. 50% will always fall into other categories (for example, the obese category). This distribution factor is a known problem of the BMI (and has been for decades), and is – statistically – completely expected. 

Skeleton with veins drawn onto it
Photo by John Jackson on Unsplash

Lean Muscle vs. Body Fat

The second, very important, factor is that the BMI does not take into account lean muscle vs. body fat. Essentially, two people could weigh the same but their bodies could be looking completely different. A person who has a “normal” BMI is clearly seen as “healthy”. A person who is obese is seen as “unhealthy”. Studies have shown that this metric does not universally apply to everyone. In fact, there are a lot of times where the statistic gets it wrong. When applying additional measures, such as cardiometabolic ones it completely tore the picture apart and established that a lot of people in the “normal” BMI category were actually not at all that healthy (by the standard that was assessed). Additionally, the BMI does not take into account the location of body fat. Fat accumulating in the upper part of the body carries significantly more risks for the development of Western diseases than in the lower body.

Female jumping over a cliff
Photo by Sammie Chaffin on Unsplash

Does Not Take Into Account a Person’s Health History

Just like predicting mortality rates, the BMI also does not take into account a person’s health history, mental illness, pre-existing conditions, smoking, alcohol abuse, or similar. All of those can strongly influence a person’s mortality and how healthy (or not healthy) they truly are. 

Different kinds of oranges on a cutting board
Photo by Edgar Castrejon on Unsplash

What Does All Of This Mean?

There are a few really good takeaways from this deep-dive into the BMI:

  • The BMI is primarily used in order to provide a statistic and should not be a universal measure for “health”
  • There are some indications that the higher your BMI, your risk for common Western diseases, including type 2 diabetes is increased. BUT this measurement is not the end-all and be-all and I wanted to send this post out to you as a reminder
  • You are so much more than your body weight divided by your height squared. And there are certainly a lot of other indicators and factors that can likely assess your health more accurately (blood work, for example)

If anything, I wanted to show you that everything needs to be put into context and albeit widely adapted this tool is not the end-all and be all of your health. Everything has to be put into context and the BMI is, unfortunately, one that oftentimes is not used in that same context of a holistic picture.

The beautiful cover photo is by Samuel Regan-Asante on Unsplash.

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