Why the Body Mass Index (BMI) tells us nothing about health. An exposé.
*Trigger Warning: this blog post discusses weight and body changes, which may be triggering for some readers.
You’ve probably heard all about the BMI – the calculation that supposedly tells us if we are “healthy” or not.
But did you know the formula was never even meant to be used to assess an individual’s health?
The BMI was developed in the early 19th century by a mathematician (note: not a physician). He created the formula as a quick and easy way to measure the average weight of a population. He, himself explicitly stated the BMI is “inappropriate for individual evaluation” and it was designed only for the purposes of statistics, not to measure an individual’s health.
The formula was developed based on the measurements of French and Scottish male participants. In other words, it was created exclusively by and for white Western European men. It doesn’t consider a multitude of factors, and therefore, can’t be considered a good indicator of health. Even those who support the use of BMI admit that it has its problems…
So, why is the BMI not a good indicator of health?
It does not distinguish between different types of body mass
The BMI is based on two factors – height and weight. It does not distinguish between muscle mass, fat mass or bone density. A great example is in athletes. Using the BMI calculation alone, many athletes such as footballers would be classified into a higher BMI category because of their greater muscle mass, even though they may be considered healthy and physically fit.
It does not consider genetics
As we mentioned before, the BMI formula was created based on French and Scottish male participants. It doesn’t account for differences in ethnic and racial groups, age, gender or ability. For example, women need more fat on their body than men to support hormonal health and fertility.
It does not consider health behaviours like nutrition and movement
The BMI calculation simply doesn’t give us enough information to determine someone’s health. Time and time again the research shows us that health behaviours, regardless of weight or BMI, improves the health of individuals. Things like how we move and fuel our bodies, manage stress and what our sleeping habits are like.
A ‘normal’ BMI doesn’t necessarily mean someone is healthy and an ‘overweight’ BMI doesn’t mean someone is unhealthy. Our health simply cannot be defined by a number – it includes various other aspects than just what we look like or how we fit into an arbitrary category.
So, what are some better indicators of health?
- What are my sleeping habits like?
- How do I manage stress?
- Do I participate in movement I enjoy?
- Am I fuelling my body with satisfying and nourishing foods?
- Do I practise positive self-care habits?
Put simply, the BMI (a.k.a. Bullsh*t Measurement Indicator) tells us absolutely nothing about a person’s health. Zilch. Zero. Nada.