Why BMI is flawed — and how to redefine obesity
Why BMI is flawed — and how to redefine obesity
The main diagnostic test for obesity — the body mass index — accounts for only height and weight, leaving out a slew of factors that influence body fat and health.
The main diagnostic test for obesity — the body mass index — accounts for only height and weight, leaving out a slew of factors that influence body fat and health.
BMI isn't really flawed, it's misused.
It wasn't created to be used with individuals. It was created as a statistical tool to compare populations.
It doesn't really work at that either.
You can't use it tell if soccer players are fatter on average than rugby players or if Japanese people are fatter than Samoans. Or even if men are fatter on average than women.
But these are population questions.
I think that's just more examples of it being misused. BMI may be useful to compare populations in certain instances. It has value in being easily calculated based off data that is often easy to obtain. But, there are many situations where it would be inappropriate to use BMI for statistical comparison. That doesn't mean it's entirely useless.
You can use it after controlling for the variables that would otherwise skew it.
Comparing different sports with different muscle requirements, or different genders with different muscle development, would be a wrong use.
Comparing averages of samples of Japanese vs. Samoans, with the same ratio of males vs females, sporty vs non-sporty, and a similar age distribution, would be a viable comparison.
INB4 genetic differences between Japanese vs Samoans:
"Over the period of 1978-2013, in a population of approximately 200,000 Polynesian people, the prevalence of obesity increased from 27.7% to 53.1% in men (2.3% per five years) and 44.4% to 76.7% in women (4.5% per five years)"
BMI is worthless for determining obesity, or fat content in general. My BMI states that I'm obese. I have 13.5% body fat, which is in the athlete range for men. Muscles are heavy.
I'm obese, and I know it. My BMI has been getting better and better as I've been losing weight, but I've been losing muscle at about the same or faster rate, which is causing a lot of problems. My waist-to-height ratio is also hilarious, because as I've been losing weight, most of the fat is concentrated below the waistline, so the ratio is great, but completely useless. I've been more fit at a higher BMI and weight.
Still, recently I got told an even worse formula: "height in cm - 100 - 10%", which would put my "optimum weight" at the top of the "healthy BMI" range... and would make someone 100cm tall into a ghost 🧐
I just use my eyes. I can tell you if you're a fatty, I have a lot of experience from when I used to go bar hopping.