Time to ditch BMI when tackling obesity?
I doubt the name Adolphe Quetelet means anything to you, it certainly didn’t to me, but in the past he has told me I am overweight. Thanks.
I can’t take this up with him due to the fact he died 143 years ago, aged 77, in 1874.
So, how did this happen? Well, I am being a little facetious, but the Belgian astronomer, mathematician, statistician and social scientist developed what he called ‘Social Physics’, which is now commonly known as the Body Mass Index, or BMI. The term BMI was coined in a journal article in 1972 by Ancel Keys as concerns regarding increasing obesity in prosperous countries developed.
This measure, which many of us will be familiar, uses weight and height to give a numerical value to state if someone is underweight, normal, overweight or obese. Even then, Keys suggested that that while the measure was not fully satisfactory, it was ‘at least as good as any other relative weight index as an indicator of relative obesity’. Despite these early reservations, it is still used as the principle method of diagnosing obesity.
One of the principle concerns with the measure is that it can be very misleading when applied to some individuals. It is particularly inaccurate for people with a high level of fitness or athleticism. For example, due to muscle being denser than fat, muscular people with little body fat can be deemed overweight. BMI only tells a portion of a persons health story, and therefore it is inappropriate to view it in isolation.
One of the other main concerns about using BMI, especially with people that are obese, is that while it may tell health professionals how relatively big someone is, it doesn’t give any indication about what is happening internally. People with a BMI of 30 or over are deemed clinically obese, but could have normal blood pressure, metabolic functions, cholesterol levels and liver function. Conversely, people with BMI’s under 30 could have underlying problems related to their size that are missed due to their BMI.
It is for these reasons that Dr Sharma, an obesity researcher from the university of Alberta in Canada, would like to see a move away from BMI-based diagnosis to one that takes into account an individuals physical, mental and functional aspects. This would include checks for diabetes, problems with joints, social anxiety and depression. This approach is further justified by research in 2010 that followed 11,000 people for up to eight years, which concluded that BMI was not a good measure for the risk of heart attack, stroke or death, with a better measure was found to be the waist-to-height ratio.
The diverse nature of humans is what makes us interesting, but is also what means the application of an arbitrary scale based on height and weight, to ascertain levels of physical health, makes little or no sense. There are many factors that go into a persons well being that the only way to truly tackle any issues is to look at the person as a whole, not a formula, and then take the necessary action.