Why BMI is irrelevant
What is BMI? Short answer? Irrelevant. Long answer..? Bear with me for a short history lesson. BMI (Body Mass Index) is the measure of your height to weight ratio. It was a mathematical theory invented over two hundred years ago by an academic named Adolphe Quetelet. Quetelet was a mathematician, statistician, sociologist and astronomer. Meaning, he was not in any field that studied the human body or medicine. It was not designed to measure individuals or give specific information about one individual, rather to be used as a tool to measure entire populations and provide statistics about populations. All of this is important, because Quetelet was an academic during the early 19th Century. Racism was blatant at this time and science was no different. Quetelet himself is credited with founding the fields of Positivist Criminology, anthropometry and phrenology. All fields of racist pseudoscience that essentially stem from the belief that people of colour are a ‘subspecies’.
So the fact that even he didn’t design the BMI to be used in the way it is commonly used, says a great deal.
Quetelet designed the BMI based solely on French and Scottish participants, exclusively white men. All of Quetelet’s work on the BMI (then known as l’homme moyen’s weight – the average man), would become the basis for measurements of “ideal” weight, fitness and the justification for eugenics. The practise of sterilisation and ultimately genocide. The ‘breeding out of certain populations’.
Fast forward to the early 20th Century and Quetelet’s theory now known as the Body Mass Index (BMI) becomes a wonderful tool for Health Insurance Companies. Based on nothing but the BMI and a flawed table, Health Insurance Companies began to charge their policyholders fees depending on their body size.
After the Second World War, the medical profession began to discover certain health conditions correlated with higher weight. So the hunt for a better measurement of weight came along. Enter Ancel Keys. Keys is also responsible for the ‘fat graph’. The graph that led the world to fear fat for half a century. Keys conducted a study (again exclusively on men), but this time he included men from the US, Finland, Italy AND Japan and South Africa. Keys again did not intend the BMI to be used on individuals. Like Quetelet, it was intended to be used as a measure of entire populations. Funnily enough, the South African men from the study were found to be ‘not representative of, or applicable to..” in the findings. So although they were included in the study, they were discarded when they were found not to ‘fit the findings’.
However, the BMI continued to be used by medical professionals, health insurance companies and now health and fitness professionals to measure and determine health in individuals. It is even used on children even though children were never intended to be or included in any study. It is used to measure the health of women even though women were never included in any study. And it is used on people from all different ethnicities and backgrounds. Even though many ethnic backgrounds were not included in the studies and where they were, they were discarded due to the fact that they did not fit the findings.
Studies as recent as 2011 found that BMI only accurately diagnoses obesity about 50% of the time. Studies show that those considered to have health risks due to being diagnosed as obese by the BMI standards, particularly those from Black communities are grossly overestimated and grossly underestimated for those from Asian communities. BMI also does not account for body weight/body fat differences relating to gender.
All of this is before we even begin to discuss the fact that BMI does not measure body fat vs muscle. In particular someone who spends a lot of time lifting weights and is very high in muscle mass but is determined to be obese using the BMI. Another reason why it should not be used by fitness professionals.
So where does that leave BMI? I think it’s relatively obvious that BMI has never had a place in mainstream medical, health or fitness fields. Nobody can determine your health based on a mathematical equation. Not even if it includes your weight. I have discussed many times the reasons that as a fitness professional I choose not to weigh or use baseless forms of information collection such as the BMI. But this should give you a real insight into just how irrelevant it is. You should always question any professional who requests you to stand on the scales, measure your BMI or waist to hip ratio. Ask what that information is going to tell them. Is it going to tell them why you have hip pain? Is it going to tell them why you have pain in your abdomen or why you have a persistent cough? When it comes to fitness professionals, many will use the argument that it gives them something to measure results by. My question here is this. Why are your results being measured by your size? And what happens when your BMI goes up because you have gained muscle mass? Or what happens when your number goes down on the scale but returns again (because it always does). How does your size tell them how healthy you are?
Your health is not measured by your size. Your worth is not measured by your size. If you want to measure your results, measure your strength gains in the weights room. Measure your cardiovascular fitness and how easy it is to do 10 burpees or run 3kms or carry 3 loads of washing up and down the stairs.
BMI was never intended to be used as a measure of health for individuals. Not even by the guy who invented it who was a total racist and misogynist. ‘The Average Man’. Remember that next time someone asks you what your BMI is.