People Are Just Figuring Out How BMI Was Originally Calculated

BMI may claim to be a health indicator, but it's more like "Bogus Measurements Incorporated" when it comes to accurately assessing many people’s wellbeing.
Body mass index (BMI) has long been used by the medical profession as a way to determine whether you are healthy, and although simple to work out, it also comes with a long list of negatives. How BMI was originally created may come as a shock to some people.

Back in the 1800s, there was once a mathematician (not a physician) called Adolphe Quetelet. His aim was to define the characteristics of a “normal man”, so as you would imagine he collected data on white Belgian men’s heights and weights at different ages and used this to come up with a calculation that ended up being called the Quetelet Index – it was eventually renamed BMI years later. Simply put, a BMI score is worked out by taking a person’s height and dividing it by their weight.

There are many flaws with this calculation that are causing scientists to reevaluate it. Firstly, it was designed with Belgians in mind so it may not be straightforward to apply to other populations. Secondly, it does not discriminate between fat and muscle. Someone with an athletic muscular build could be labeled as "unhealthy" despite having limited subcutaneous fat. Thirdly, it was created on calculations made from men's data, and no woman was included in the original equations.

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Despite all of this, medical professionals are still using BMI as a measure of "fatness", where a BMI between 18.5 and 24.9 is classed as "healthy", and anything outside this range is not.

It is even being used to put a cap on eligibility for surgery and treatments. Some plastic surgeons decline to operate on people over a certain BMI. In some places, there is even a cap on fertility treatments. For example, one of the symptoms for polycystic ovary syndrome (a very common cause of infertility) is weight gain; but despite this, in most places in the UK there is an NHS cap of a BMI of 30 for anyone wanting to undergo IVF treatment. This forces many to go through expensive private treatment where the cap is a bit more lenient.

So how did we even end up using traditional BMI as a health measurement?

It was in the 1940s when the vice president of Metropolitan Life Insurance used the BMI to develop tables that helped predict the death rate of obese policyholders, and therefore any resulting insurance payouts. Due to the ease of use of the metric, health policymakers soon took up the scale as a way to have a rough guide to someone’s health status.

Luckily, times are beginning to change. The World Health Organization has suggested different cut-off points for Asian populations due differences in obesity-related health risks in these groups. The BMJ has also proposed that BMI alone should not be used to assess patients' weights.

There are also new BMI calculations being proposed. One such calculation is called the biological BMI, from scientists from the Institute for Systems Biology. The study is based on multiomic profiling of blood samples from 1,000 individuals. Machine learning tools are used to generate the molecular score.

“Biological BMI is a multi-dimensional molecular measure of BMI calculated from blood measurements of proteins, metabolites or clinical labs. It is a more comprehensive and accurate measure of metabolic health compared to the traditional BMI measure, which only considers height and weight. Unlike traditional BMI, biological BMI can identify misclassified individuals with a normal weight but disrupted metabolic health, who may not be currently monitored or treated,” first author of the paper Dr Kengo Watanabe told Technology Networks.

There is still a long way to go in BMI research. But, hopefully, in the future, the traditional BMI will scrapped and more accurate scores will be implemented.

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