BMI – we’ve all heard the term before. It stands for Body Mass Index and is what most doctors use to classify healthy body size. Here’s how it works: using just 2 metrics (height and weight) put into a formula (kg/m²) it assigns a number to your body size; then using the criteria below, it determines if you’re at a healthy weight.

<18.49 = underweight

18.5 to 24.99 = normal weight

25 to 29.99 = overweight

>30 = obese

The Good BMI News

It’s been around since 1830 when they were still using abacuses (abaci? – it’s too old for this to be common vernacular), so we’ve got over seven generations of data to work with. 

This is great news when it comes to measuring populations on a grand scale and determining trends overtime. Because of BMI’s simplicity in requiring only those two data points, it’s super simple for healthcare practitioners to capture this data at every appointment. This means the ‘database’ of all BMI measures continues growing at an astounding rate! 

The resulting data is enough to draw real conclusions and make well-informed decisions regarding policy, education, and ‘norms’ for populations. Decision makers can use actual data on which to base their proposed legislation (doesn’t mean they WILL use it, but it’s available), and provide measured deliverables to determine success. 

So, if we’re wanting to generalize across a population, BMI can be a great tool. And to be honest, BMI is the best tool (for now) we have to measure the 7.7 billion – and counting – people in the world.

The Bad BMI News

If you thought there would be more good news than that, I’m sorry to disappoint. From here on out it’s the bad and the ugly.

I’ll begin with the obvious – there are only two metrics taken into consideration. While it’s great for ease of data collection and thus the volume of data, there’s more than one body type among our 7.7 billion residents. 

BMI measure doesn’t take into account gender, age, tissue type, bone density, or anything else… it’s literally 2-dimensional. This leaves much to be desired for determining an individual’s healthy body weight versus a population’s healthy body weight. 

The resulting mis-classification can happen to a lot of people (like ~75 million), leaving some thinking they’re overweight/unhealthier than they actually are; and others thinking they’re healthier than they actually are. 

Another of the bad of BMI is it places ALL the emphasis on weight – we can’t change our height, so to change our BMI we have to alter our weight. This leaves BMI worshipers ignoring a litany of other health factors that should also be taken into consideration. 

For example, not just total weight, but WHERE people carry their weight can have different health implications. Those who carry excess weight around their midsection have been shown to have higher cardiovascular health risk versus those who carry excess weight around their hips and thighs (so go on with ya bad self if you’re rockin those hips!).

The Ugly BMI News

Despite all the above, you shouldn’t just ignore your BMI. While it may not be spot-on for you as an individual, it does give you a guideline of sorts to follow. I certainly don’t mean to use the BMI scale as the end-all be-all of your health measure. Instead, use it to track progress over time in conjunction with regular checkups with your primary care physician.

I’d also like to point out that nowadays with the U.S. obesity epidemic, we don’t need a statistical measure to tell us we’re overweight – most of us know if we’re carrying around some extra pounds. Over 70% of all adults in America over the age of 20 are overweight or obese, so odds are we don’t need to know our BMI to figure out if we’re in the 70% or the 30%.

Not to mention, we can usually FEEL if we’re overweight – our body wasn’t built for the way we live and eat nowadays so it has ways of clueing us in. Do your bones and joints ache? Are you constantly low on energy? Do you have trouble sleeping? All those things can be indicators, we just have to listen.

So while BMI has way more ‘bad’ than ‘good’ (seriously, WAY more bad), the ugly part is that it’s going to stick around for the foreseeable future. And given that we have so many generations of data to work with, we might as well use it to our advantage rather than complain about all the flaws. We can use it for what it is – one tool (of many) that can help us get on the right track. 
If you’re trying to improve your BMI (among other health indicators), grab my workout template – with links to my exercise videos included – to remove the excuse of not knowing what to do each day.

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