Is BMI Accurate? Why We Use It.
Sometimes I meet people, usually well-intentioned health and fitness professionals, who criticise Sejuta.KG, saying that focusing on losing kilograms and reducing BMI is “out-dated” or “irrelevant”, especially to the health aspirations of men building muscle.
They cite examples such as Dwayne “The Rock” Johnson, who has a BMI of over 30, which would technically put him as obese – now, how can someone like him, at the pinnacle of health and fitness, be considered obese?
At SejutaKG, we do agree that we should never pursue only one health metric and ignore all others, and that includes your BMI. What BMI is trying to get at is a measure of fat as a percentage of your total body composition, but that can be difficult to measure regularly and verify for prize-giving purposes.
Tracking your weight or your BMI, on the other hand is a useful proxy for body fat because it is easy to measure and for most of us it serves well as a tool for checking progress in our efforts. The real challenge is how to translate different health goals and metrics into kilograms gained or lost, if possible.
There is one metric, though, which can work for all of us – your waist measurement. If you take a tailor’s measuring tape (or even one of those free IKEA ones) and measure the circumference around your waist (relaxing your abdomen and circling the tape around your hip bones and belly button) – then divide the result by your height, you will find an even more accurate proxy of your body fat percentage – which is the ratio between your waist to your height.
This ratio is now becoming increasingly accepted as a good indicator of your fat percentage and therefore your risk of early death from obesity-related diseases (because fat tends to collect at our belly for all of us, men or women, young or old, body builders or non-body builders). Doctors and scientists have determined that your goal should be to reach a ratio of 0.5 and below – your waist should, ideally, be less than HALF your height.
Now here is the interesting part. We can also estimate how overweight you are for every cm your waist is above this ratio. Every cm of excess waist length is about 1.1kg of excess weight.
So, for instance, if your height is 170cm, your ideal waist circumference should be 85cm. If your actual waist circumference is 90cm, you have (5cm x 1.1kg) = 5.5kg of weight to lose.
So, even if you are a body building enthusiast – you too can still contribute to our SejutaKG campaign and win some prizes, by losing 5.5kg - and you would definitely be getting healthier too!
In case you’re still not convinced, here are Dwayne Johnson’s vital statistics from publicly available sources: https://starsunfolded.com/dwayne-johnson/
You can see his waist is 89cm and his height is 188cm, giving a waist to height ratio of 0.47.
Yup, The Rock truly is at the pinnacle of health and fitness. We can certainly agree on that, whatever our stance on which health metrics to follow!
Postscript:
So why doesn’t SejutaKG change its name to SejutaCM and measure waists instead? Simple answer: it’s too hard to verify on video. The slightest tension in your tummy can “erase” many cm from the measurement! If we can’t verify properly - we can’t give prizes confidently. So we will stick to KGs.
Sources;
https://www.theguardian.com/.../ensure-waist-size-is-less...
https://theconversation.com/the-mathematics-of-better...
https://starsunfolded.com/dwayne-johnson/