Body Mass Index (BMI)

With the 2015 Rugby World Cup starting this evening, it might surprise you to find out that the BMI of a lot of the competing athletes would tell us that they are obese. Yet the BMI is still the most popularly used measure to determine whether someone is is healthy or not. Surely we are missing something?

The frequent use of a persons BMI has continued despite numerous criticisms being repeated again and again on all forms of media. And there are plenty of flaws to pick up on. The ones you hear the most are that it is just too simple, it’s inaccurate or that it doesn’t consider all the factors that play a part on our overall fitness level. 

So let’s take a closer look. Firstly, when you are using a measure that uses just two pieces of information you are invariably going to be neglecting a lot. When you are just giving your weight as a whole you aren’t considering what is contributing to that number. Because while fat will be playing a part, so will muscle. So the more muscular someone is, the more likely it is that their BMI will be inaccurate. 

Let’s be honest, while the simplicity of the BMI is a flaw it is also probably the reason why it is so popular. Humans love to be able to just simplify anything down to one number that fits somewhere on a scale and that’s exactly what the BMI does. 

But what else is being neglected? Here are just a few things:

• Age
• Gender
• Amount of physical activity
• Body fat percentage
• Genetics
• Other health conditions

And the list goes on. In reality it is impossible to get to one number that will be able to consider all of those things. So we can’t demand simplicity and expect thoroughness as well. 

I guess we need to think about how often this inaccuracy occurs. Almost all the time for athletes unfortunately. Their comparatively high levels of muscle mass mean that their weight is always going to suggest that they are overweight/obese in terms of their BMI. The fact is that two people who to everybody in the world look completely different could have an identical BMI. You can’t use the number to give you an idea of what the person looks like. An Olympian who stands 6ft tall can have the same BMI as somebody who spends their life sat in front of a television, conducting little/no exercise.

Of course there are alternatives out there. Recently we have seen a lot more people switch to the waist-to-height ratio instead. The problem that a lot of people have with the BMI is, as I mentioned above, that it doesn’t consider what is contributing to a persons weight; be it fat or muscle. So by comparing someone’s height to their waist size instead, you are removing the issue of weight completely. Not only that, you are also getting an idea of the amount of visceral fat that a person has, which can be directly linked to health problems later in life. 

If you don’t like BMI then don’t even bother looking yours up. That’s my advice. Most people will know how healthy they are, assuming you don’t have a condition that hasn’t been diagnosed. You know if you are overweight, you know if you don’t exercise enough and you know if you are eating the wrong sorts of foods. So you don’t need a number to tell you something that you already know.