BMI doesn’t measure Body fat content (which you think would be essential), muscle mass, bone density, overall body composition and finally racial and gender differences.
True Story (how this affects you)
Let me tell you another story, this one is a true story and happened to one of my Clients, who we will call Bob.
Bob has on average 1-2 Personal Training sessions with me in Harrogate on a weekly basis and he may go for a run on the weekend. The Business he works for are very generous and care about Bob’s health. Once a year he gets a full body assessment at Nuffield Health Hospital, where they will test his body fat %, core strength, posture, stress and general fitness. On his last visit Bob found that his body fat % had stayed the same as last year (17%) which is a good healthy range. He also found that his body weight had increased by 2kg. Considering his body fat had not fluctuated we can safely say that Bob had increased his lean muscle tissue. Increased muscle tissue means increased metabolic rate! This means, more energy spent at rest and therefore we can chip away the infamous body fat % a lot faster. Happy days!
Bob has Health insurance through his company too! This company rewards good health with cash pay outs, which is awesome, right?
However when Bob received his health checklist, he scrolled through the copious green ticks, non-smoker, blood sugar levels etc and finally came across the final box BMI, with a red cross…
Bob was now 2kg overweight on the BMI scale. This means no cash pay-out… Bob is not rewarded for his well-earned muscle mass but penalized.
So why hasn't this system changed?
"It always seems impossible until it’s done." Nelson Mandela[tweet this].
The HARD truth...
This isn’t new, Health experts will commonly comment “BMI is flawed”. It goes through the cycle of news and then it all goes quiet again. It is a broken system that doctors still use to measure your health. It promotes healthy individuals to lose muscle mass for fear they may be labelled as overweight. Minimal muscle mass in the long term means a slow metabolic rate and eventually fat stores will start to rise. It is extremely hard to get your metabolism burning from a stand still!
Muscle mass weighs more than fat (it is denser, per cubic inch of muscle weighs more than a cubic inch of fat). Therefore, BMI will inevitably class muscular, athletic people as fatter than they really are.
Even using BMI for less active people can be a flawed system. As there is no compensation for difference in height it can skew the results for taller people making them believe they are fatter than they really are, and shorter people appearing thinner on paper than in reality.
Circumference Measurements are a good simple way to measure body fat but it can depend mostly on the individual and their body shape. Using a combination of measuring techniques are the most effective and then taking a calculated reading from all measurements. This can be from skin fold measurements, circumference and body stat machines (although these can be consistent in being inconsistent). This is why an initial consultation with a personal trainer is so important. The trainer can gain a good understanding of a client’s current health and also their needs for training from these measurements.
Historically, BMI was created in the 1830s by Lambert Adolphe Jacques Quetelet (1796-1874), a Belgian mathematician, sociologist, statistician and astronomer. 200 years on with all the technology available to us, why haven’t we come up with something more efficient to be standardised across the medical society?
Sean Baldwin is the founder of Tri Force Training, a Personal Training service in Harrogate.