• Rosie Tatham

Goodbye, BMI: the damaging health measurement that needs put to rest.


Illustrations by Megan Le Brocq


Medicine and healthcare are undeniably a key part of society, yet there are inherent flaws within our system that have been accepted for far too long. A simplistic mathematical calculation, the Body Mass Index (BMI), is used as a legitimate medical tool to diagnose, explain, and disregard people’s health. However, it is now time that this stops.

Weight/Height2 (the formula for the BMI) has become the global standard to diagnose obesity, mental health disorders such as anorexia nervosa, and assess risks of cancer or cardiovascular diseases. It’s simple and cheap, making it an easy tool for doctors to use. However, its simplicity is also why it’s inadequate in diagnosing these complex diseases— it solely relies on weight and height, rather than the multitude of other factors that indicate health. Additionally, it is haunted by a questionable history which further reinforces the need to revolutionise how we assess health.

In the 1830s, Lambert Quetelet, a mathematician, sociologist and astronomer (notably not a doctor) produced the BMI formula. He did not derive this equation to be used for individual medical purposes, but instead intended to measure what he perceived as the ‘average man’ (l’homme moyen). He focused his findings on Caucasian men alone and the averages that he calculated were branded as the ‘ideal’— any deviation from this was regarded as a ‘deformity or disease’. Despite the clear racist and sexist roots of this formula, the social and technological advancements of the last century have been dismissed for the sake of simplicity.

The BMI continues to be used incessantly with minimal adaptations, leaving our medical system biased against anyone who isn’t a Caucasian man. This indiscriminately affects women and ethnic minorities— their health problems are disregarded by being flippantly told to ‘just lose weight’ as their BMI is ‘too high’. The reverse is just as problematic, with people being denied treatments for mental illnesses such as anorexia nervosa— their BMI measurement not being considered ‘low enough’.

You will probably have seen the BMI chart plastered on the walls of GPs across the country. The strictly coloured number boundaries dictate the care you can receive if you attend the GP for a health problem. If you have a mental illness, such as an eating disorder, a BMI of under 17.5 is medically considered a ‘symptom’ of the illness and criteria for accessing NHS psychological treatment. Only 6% of people with eating disorders are underweight, therefore, continuing to use the BMI for diagnosis means thousands of people are not receiving adequate treatment. Individuals not believing they are ‘thin enough’ and therefore ‘sick enough’ for treatment is a common symptom of an eating disorder. Hence, being told they do not fit the ‘criteria’ through the BMI’s arbitrary scale only exacerbates these dysmorphic body images. Using a calculation of the body to ‘diagnose’ a disorder of the mind completely invalidates it and demonstrates the detrimental consequences that a lack a lack of funding and teaching of medical professionals about the nature of mental health can have. Moreover, the recent legal requirement of calories on menus (a whole other article in itself!) will only exacerbate disordered eating behaviour, contributing to this massive problem.

Not only is the BMI’s history and simplicity grounds enough for it to be invalidated, it is also medically nonsensical. The BMI uses just height and weight, not accounting for pretty much every other factor that determines health— genetics, hormone differences, sex, race, bone density, muscle percentage, fat distribution and more. It ignores hormonal and genetic differences between the sexes – healthy women should have 10-13% body fat compared with men who should have 2-4%. Additionally, muscle is denser than fat, therefore someone with high muscle mass will show a similar BMI to someone who is overweight. Although, on a population level a high BMI does correlate with a risk of diabetes and cancer, all of the other factors are ignored, and the cause is automatically placed on weight. This perpetuates societal fatphobia, blaming every health problem on being above the ‘normal’ BMI. As a Biomedical sciences student, we are constantly taught that correlation does not mean causation, however, when it comes to our health system, it seems they are falsely believing that correlation does in-fact mean causation, dismissing better alternatives. Evidently, weight is an illogical metric, yet it is placed at the centre of campaigns such as the UK government’s ‘Better Health’, which emphasises lowering your BMI as the way to achieve ‘perfect’ health. It is also used to define obesity in America, enhancing the fear mongering narrative around their ‘obesity epidemic’.


We are now 200 years on from the BMI’s invention and have the technology and resources to use much better alternatives. Blood tests, MRI scans and X-rays are just a few examples of extremely accurate tools that can be used to discover and diagnose health problems. However, these resources aren’t as simple or cheap as the BMI, which is how healthcare providers justify its use. This may also explain why there are no efforts to create new strategies. Fundamentally, any method, even other imperfect ones such as waist-to-hip ratio or waist-to-height ratio are more effective than the BMI.

The BMI indicates nothing more than a tiny fraction of the population’s height and weight from 200 years ago. Until this archaic calculation stops being used, millions of people will continue to be medically discriminated, neglected, and side-lined.


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