Many of us are likely familiar with the term BMI, which stands for Body Mass Index. The Body Mass Index is a method of measuring adiposity – it is a simple calculation that takes an individuals’ height and weight and plugs it into an equation, assigning them into a category based on this number – underweight, normal weight, overweight, obese, and morbidly obese. BMI is (unfortunately) common practice in primary care clinics and doctors offices, and is even introduced in high school health classes (incredibly problematic when we think about the risks of disordered eating in this population – added fuel to the fire).
But as we’ll dive into in this article, BMI was never designed to be used at an individual level, is unable to account for other body composition and lifestyle factors, and is particularly harmful and inaccurate for anyone who isn’t a white male.
Because the truth is, BMI is lazy medicine at best and harmful at worst. Most people in healthcare acknowledge some of the limitations of using BMI, but fail to see just how impractical and harmful it can be.
A Brief History on the Origins of BMI
The Body Mass Index was invented by Adolphe Quetelet, a Belgian mathematician, statistician and astronomer. Read: not a doctor or professional at all interested in health! The origins of BMI came from Quetelet’s work in trying to statistically define the characteristics of the “average man” – an attempt to categorize populations, not individuals. It’s important to note that this doesn’t refer to average in the sense that we might use today (i.e. mediocre) as is illustrated in this quote from Quetelet:
“If the average man were completely determined, we might consider him as the type of perfection; and everything differing from his proportion or condition, would constitute deformity or disease…or monstrosity.”
– Adolphe Quetelet, A Treatise on Man and the development of his aptitudes
Yikes. So really, he was attempting to evaluate the anthropometric measurements of the “ideal man”, and determine how much variation from this ideal existed in the population of that time. BMI was initially called “Quetelet’s Index”, and Adolphe Quetelet developed his formula for this index (weight/height2) by exclusively studying French & Scottish participants (read: white Western European males). Again I want to emphasize that this model was designed for statistical modelling and was not intended by its creator to be used on individuals! In fact, it wasn’t even designed to measure health in any capacity, but rather an objective way of relating height and weight in populations, and fitting this data onto a bell curve.
Moving forward through history, Quetelet’s Index seemed to be lost until it resurfaced in the research of Ancel Keys in 1972. Keys renamed the formula to Body Mass Index, as we know it today. Shortly after this, in part thanks to insurance companies adopting weight classifications for determining life insurance policies, BMI became widely used by healthcare professionals at an individual level. The BMI ranges have been tightened since the 70s, resulting in more and more people being “classified” as overweight or obese.
I would highly recommend that you click through and read this article that dives deeper into the origin story of BMI and a description of the social context to help you better understand its problematic use today.
4 Reasons Using BMI for Individuals is Problematic:
#1 It forces all individuals to conform to Euro-centric standards.
Given what you just learned about the origins of BMI, and the fact that its entire premise was based on the study of white European males, can you see how this measure attempts to whittle down body diversity into a one size fits all algorithm?
Science has repeatedly demonstrated that this measure built by a white man and designed to categorize white men is inaccurate for individuals who are anything but that. For example, research has shown sex-based differences in the relationship between body fat and BMI, meaning that we need to consider body composition differences between males and females rather than applying one equation to all!
For People of Colour, the widespread use of BMI may lead to misdiagnosis or mistreatment. Research has shown that BMI overestimates fatness and health risks for Black people, while on the other hand, BMI may underestimate health risks for Asian communities.
#2 BMI doesn’t distinguish between different types of body mass.
Calculating an individuals’ BMI tells you nothing about their distribution of fat mass, lean muscle mass, bone density, and tissue. So for many people, this measure is (even more) wildly inaccurate. For example, athletes who often have higher amounts of lean muscle, are often classified as having a higher BMI. Individuals who have a larger frame, or higher bone density (a good thing!), can often be classified as having a higher BMI.
#3 BMI has played a role in pathologizing body sizes.
The BMI cut-offs have played a large role in pathologizing bodies and assigning disease (i.e. obesity) to body sizes that naturally exist, even when individuals are engaging in health promoting behaviours (moving their bodies regularly and eating healthy). Bodies exist in a wide range of shapes and sizes, and rather than celebrating that diversity and focusing on care for each and every body, the widespread use of BMI plays a role in institutional policies that results in weight stigma and the harm associated with this.
#4 BMI ignores health promoting behaviours.
Even some of the biggest proponents of using BMI can admit some of its limitations (as discussed in point #1). So why is it still used? The argument is often that it is a simple, quick, and inexpensive method of measurement in a doctors office. But you know what else is quick and simple? Asking someone about their fruit & vegetable intake, movement patterns, alcohol & smoking history. These are just a few health promoting behaviours that can tell us so much more about a person’s overall health. Because weight isn’t a behaviour. Imagine how different a doctor visit might look if this was the focus versus an arbitrary mathematical calculation that is inherently flawed and wasn’t designed to be used for individuals and doesn’t account for genetic diversity?!
If you’ve been told flippantly to lose weight, without a thought given to your lifestyle or behaviours, I am deeply sorry. By equating weight with health, we take the focus away from engaging with and encouraging health promoting behaviours, which we know promote long term health. This unfair conclusion fuels weight stigma, which research has shown can lead a person to engage in more negative health behaviours such as fad dieting and weight cycling, and do far more harm for their long term health! This is why in my practice, I take a weight-inclusive approach. I am far more concerned about your health behaviours – your sleep, stress, nutrition, and movement – than I am about a number on the scale or a BMI category.
Looking to read more about the BMI and different (read: better) ways of measuring health? My friend and fellow dietitian Emma did a wonderful 3 part series on this: check it out here, here, and here!
References:
Angela Lemond:,Why BMI Is Flawed and the History Behind How the Scale Came to Define Obesity. Retrieved from https://www.everydayhealth.com/diet-nutrition/bmi/bmi-flaws-history-other-ways-measure-body-weight/
Frank Q. Nuttall, Body Mass Index: Obesity, BMI, and Health: A Critical Review. Nutrition Today. 2015; 50(3):117-128. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4890841/pdf/nt-50-117.pdf
Garabed Eknoyan, Adolphe Quetelet (1796–1874)—the average man and indices of obesity, Nephrology Dialysis Transplantation, Volume 23, Issue 1, January 2008, Pages 47–51, https://doi.org/10.1093/ndt/gfm517
Sylvia R. Karasu, Adolphe Quetelet and the Evolution of the Body Mass Index (BMI). Retrieved from https://www.psychologytoday.com/us/blog/the-gravity-weight/201603/adolphe-quetelet-and-the-evolution-body-mass-index-bmi
Leave a Reply