Uses of BMI

It seems that no matter what health or fitness website you go on, there will always be a BMI calculator and then some information on the uses of the BMI calculation that it came up with.

I won’t bore you with the entire history of the BMI but just a few key points that are worth going over.

The Body Mass Index (BMI) was originally known as the Quetelet Index and was invented (shockingly) by a guy named Quetelet in 1832.

His goal was to:

describe the standard proportions of the human build—the ratio of weight to height in the average adult.

He did this by:

Using data collected from several hundred countrymen, he found that weight varied not in direct proportion to height (such that, say, people 10 percent taller than average were 10 percent heavier, too) but in proportion to the square of height. (People 10 percent taller than average tended to be about 21 percent heavier.)

The interesting part is that Quetelet didn’t intend for this equation to be used as a way to define obesity or define whether someone was more at risk for obesity related diseases.

Maybe even more importantly, he stressed that information obtained from BMI measurements were more reflective of POPULATIONS and not for individual assessments.

In other words, the way the BMI equation is today is not what it was originally intended to look at.

Presently, it’s almost considered the gold standard in how you are assessed, health-wise.

There’s the added issue that someone with a low body fat but with a lot of lean mass could be considered overweight with following the BMI.

I’ve gone back and forth on what I think about the uses of BMI. Although it’s not being used the way it was originally intended, and it might not be accurate for those with a low body fat percentage, for the most part, I think that it is still an fairly accurate assessment of an individuals “fatness” for 98% of the population.

But, there is a “new” health assessment that is getting some fanfare. It’s called the Weight-to-Height Ratio (WHtR).

To determine your WHtR), you simply take your waist measurement, in inches (at the belly button), and divide it by your height, in inches. The link above will give you a breakdown of what your number means.

The reason this might be a better measure of heart disease risk or other risk factors is because abdomen fat has been found to be more of a predictor of cardiovascular health.

"The size of the hips seems to predict a protective effect. In other words, a big waist with comparably big hips does not appear to be as worrisome as a big waist with small hips," said Dexter Canoy, M.Phil., M.D., Ph.D., a research fellow in epidemiology and public health at the University of Manchester in the United Kingdom.

Although I still think that there are uses of the BMI for assessing overall populations and population trend swifts in how the proportions of our bodies change, I’ll be interested to see if the use of the WHtR will be more widespread in the future as it seems like a fairly good, simple measuring tool and seems to have more of a relationship to determine actual health risks.

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