Questioning the BMI
The BMI (body mass index) is a formula designed by Lambert Adolphe Jacques Quetelet, a Belgian astronomer, mathematician, statistician and sociologist. It was designed to ascertain whether one is ‘underweight’, a ‘normal weight’, ‘overweight’ or ‘obese’. This can help to indicate their risk of heart disease, cancer or diabetes (type 2) and advise the government as to the general state of the public, so they know where to allocate resources. However, upon researching, I have uncovered several worrying flaws in the system.
The BMI works by dividing a person’s weight by their height to the power of two (kg/m2). This works as a blanket way to compare how much weight a body carries in relation to its vertical size. The commonly accepted boundaries are:
[if !supportLists]* [endif] >18.49 - underweight
[if !supportLists]* [endif]18.50-24.99 - healthy/normal
[if !supportLists]* [endif]25.00-29.99 - overweight
[if !supportLists]* [endif]< 30 - obese
The first potential flaw arises from the fact that the system was devised in the 1830s. While the fact that it has been in use for over 100 years could be used as an argument for the strength of the index, surely it must be asked how well such an old system can really fit into a 21st Century society? When Quetelet devised it, there were no electronic devices or calculators so it had to be very simple. Now there is no need for such simplicity; furthermore such simplicity may be resulting in an inefficiency that negates the point of the system.
Most obvious is the fact that the BMI does not take muscle into account, merely a vague overall weight. It is proven that bone, for example, commonly makes up 15% of a person’s weight. Should this not be excluded from the calculation? There is also evidence that muscle is roughly 18% more dense (so weighs more) than fat, but this is not taken into account. A common example is someone of a fairly healthy, active lifestyle whose weight largely comprises of muscle. The BMI has been known to determine such a person ‘overweight’ or even ‘obese’, while it is possible for someone that does little to no exercise to have a lower BMI reading.
Through assigning a blanket scale to all, the BMI also discriminates against age. It’s designer, Quetelet, conceded himself in 1842 that to be healthy a baby’s breadth should be more in comparison to its height than later in life, with weight in relation to height cubed, not squared. The BMI does not allow for this. Not only this, what about the other end of the age range? The large majority of the elderly population are ‘overweight’, but simultaneously advised against or prevented from carrying out most weight loss strategies like running. As of July 2017, 18% of the UK population is over 65, so why do we still employ a system that does not fit at least this 18% of our population?
The BMI is a poor fit in many other ways. For example, the difference between men and women’s bodies. For 2-4% of men’s body weight to be fat is considered healthy, with 25% considered obese. In women these figures are much higher: 10-13% means healthy and over 32% means obese. If it is acknowledged that men and women’s bodies are different so why do we hold them to the same scale? A final example is the failure to take into account the location of the fat. Cholesterol and fat around internal organs typically means increased risk of heart disease and metabolic disorders. However, fat around the thighs and hips is considered less dangerous, meaning that someone with life threatening but minimal fat around their liver or kidneys could be classified as ‘healthy’ by the BMI and fail to receive the help they need. Similarly, someone with high amounts of harmless fat around the thighs could be labelled overweight, while less at risk.
All this scope for inaccuracy has caused some shocking figures. Research published in 2016 labelled 75 million Americans misclassified. Cardiometabolic tests proved 54 million of those classed by the BMI as ‘overweight’ or ‘obese’ were in fact perfectly healthy, and that 21 million of those classed as healthy were living unhealthy lives. So our system cannot even do its job. I would also like to take issue with the system as a whole. We reduce lifestyles to a numerical value, but no single number can capture the complexity of our bodies and associated health issues. While I agree that the BMI or a similar figure could be useful for giving an overall idea of health, the figure could be undisclosed outside the government and accepted as approximate. It could be used purely for population studies, for example. Currently, it is used to summarise someone’s entire medical situation even though it is often inaccurate. Many large employers use it as a measure of how healthily someone is living and even refuse to grant health insurance assistance to those with a sufficiently high BMI measurement. Should a flawed system be able to influence someone’s access to human rights?
Furthermore, the BMI is at the root of much of the fatphobia and discrimination that affects millions across the world. Those who are visibly ‘overweight’ are commonly denied jobs or simply assumed to be unintelligent, and these negative ways in which they are treated come from the government. The BMI promotes the idea that small bodies = health, which is a greatly dangerous, not to mention deeply flawed ideology. According to the World Health Organisation, the percentage of the world’s 18+ population that is overweight or obese is as high as 52. Surely there is no way our bodies should all be within one narrow range if so many are failing to be ‘healthy’? As proven, this fixation with one body type has led to a so-called health system that is shockingly unreliable. It is time to revise this system. It is time to accept that bodies do not fit one type, and that numbers will never sufficiently encapsulate the beauty and complexity of the human form.