The Simple Truth About BMI

Everyone has heard of BMI before, short for Body Mass Index. It is a tool that is used all around the world to classify people into "healthy", under, or overweight based solely on height and weight. However, several factors such as age, sex, and body type are not taken into account when assessing someone’s health using the BMI tool. Where does this term come from and why was it invented?

BMI is derived from a simple math formula. It was devised in the 1830s by Lambert Adolphe Jacques Quetelet, a Belgian astronomer, mathematician, statistician and sociologist. Notable is that Quetelet was nowhere near a medical doctor. During his work, Quetelet developed a passion for probability calculus that he applied to study human physical characteristics. He was best known for his sociological work aimed at identifying the characteristics of l’homme moyen, meaning "the average man" in French. This "average man" was Quetelet’s representation of a social ideal, an ideal Quetelet believed was the mathematical mean of a population.

His desire to quantify this social ideal prompted Quetelet to study human growth in the context of populations. These studies led him to conclude that other than the spurts of growth after birth and during puberty, "the weight increases as the square of the height". In formula, this is BMI =weight (kg) / height 2. The equation was known as the Quetelet Index until it was named Body Mass Index in 1972 by Ancel Keys, an American physiologist who studied the impact of diet on health.

A very important aspect in the invention of the BMI is the time frame in which it took place. Quetelet’s studies were published during the early 19th century, a time when there were no computers, electronic devices, or calculators that could accurately assess or examine the human body like we can do with the technology of today. He developed a system based on a simple math formula, while we now know that no number can ever capture the complexity of our bodies and associated health issues!

Not to mention, the 1800s were also a boom time for racist science. Quetelet’s studies were based solely on the size and measurements of French and Scottish men, meaning people of color, immigrants, poor people, and disabled people were not taken into account. Not to mention, zero women were part of this study! That is, the Index was devised exclusively by and for white Western European men.

By the turn of the next century, the BMI system quickly gained popularity as a tool to assess whether people are over, under, or healthy weight. Even today, BMI is used as a means to determine overall health, which is flabbergasting considering so many factors aren’t taken into account! Think about muscle-fat-ratio, bone density, body type, sex, and age. Furthermore, bodies recovering from illnesses such as eating disorders or injuries often require a (sometimes temporary) higher body fat percentage than prior to ensure proper healing. The science has disproved many common myths about size, health, and weight loss for years, so why are we so obsessed about our place on a BMI chart?

Like any other historic tool, BMI is a product of its social context. With all the technological advances made in just the last couple of decades, is it not questionable that medical professionals use something as simple as a math formula to determine whether someone is "healthy" or not? Patients with a history of eating disorders are being told they are ‘recovered’ because they have reached a "healthy" BMI. But what about the mental aspect? What about the absence of menstruation (in women) or the mental hunger indicating the body (still) feels restricted? Back in the 1800s, BMI was created solely because there was no better alternative.

Now there are so many different measurement tools, you can get a pretty good image of someone’s well-being when put together. From a quick blood draw, doctors can notice any deficiencies or surpluses in the body and even how well certain organs are functioning! More often than not, however (assuming you have no chronic illness), the best "markers" of health are as simple as observing the way you are treating your body and listening to its signals. What are your eating and drinking habits like? How often do you get outside and move your body in a way that brings you joy? Are you getting enough sleep? Although it almost seems "too simple" to ask yourself these questions, it often is "that simple"! It’s no coincidence obesity and eating disorders were almost inexistent before we even knew about calories or diets. We seemed to do better when we knew less! 

In our current day and age, with all the fad diets, health claims, and chemically ridden additives added to our food, it can be hard to stay true to yourself our bodies. However, crunching numbers into calorie counters, ‘how much to eat in a day’ calculators, or pinpointing your place on a BMI chart will never even get you close to doing so. We have overcomplicated how to respond to something as simple as the presence of a hunger cue, which, from a biological standpoint, can create confusion for the body and end up in health complications that could have easily been avoided. As hard as it is to silence the "noise" the health industry has created and compare yourself to the millions of models and influencers on the internet (photos which are often FAKE!), one of the most important markers of health (and often very reliable!) is the way you feel; in every sense of the word!