Body Mass Index - A Way to Measure Weight & Height

The body mass index, more commonly known as the BMI, is a way of measuring a person’s weight in proportion with their height, assigning a statistical number that represents both.  While the BMI in general can be a good way to estimate the average healthy body weight for a person’s height, this is not an exact science and one common misconception is that the BMI is a measurement of body fat, which is not true.  While the BMI is an estimate of healthy body weight for height, it’s not exact at all.  The BMI of a professional bodybuilder, for example, could be high in the “extremely unhealthy” range because of all the extra weight from muscle, but that would not be an accurate description of the bodybuilder’s actual health.

The body mass index is often used in lieu of actual body fat measurements because it is easy to measure and figure out, making it more popular.  The body mass index was first used between 1830 and 1850.  The BMI is figured out by taking the person’s body weight and dividing it by the square of the height.  For weight use kilograms, not pounds, and for height use meters.  So to get the right BMI number you want to take kg/m2.  That measurement will let you figure out your BMI.

The body mass index isn’t perfect, but for average individuals it is often a relatively reliable estimate of where your weight sits health wise.  The BMI measurement became most popular in the 1950s and 1960s when obesity first started to become a serious and common problem in developed Western societies.  The Body Mass Index has come under fire recently, mostly because of its misuse.  While the BMI is a good estimate, it was never intended to be used as iron clad figures, or to be used by doctors for medical diagnosis of health.  A more accurate use of BMI’s purpose is to have it used as a simple easy to estimate means of seeing how physically active or inactive the average individual is as measured by weight in relation to height.

There are several factors that can really through off the accuracy of a BMI report.  Two of the obvious are heavy weight lifting, like bodybuilding, and extreme height.  Because of the simplicity of the math, the taller a person, the more likely the BMI is to be off.  There are several “ranges” that BMI scores fall into.  It’s generally accepted that:

BMI Categories within the healthy range:
Low 18.5-19.8
Med-Lo 19.9-21.1
Medium 21.2-22.4
Med-Hi 22.5-23.7
High 23.8-25.0

Scores under 18 are dangerously underweight, while scores over 25 indicate obesity, and go all the way up to morbidly obese.  These are once again, just general measurements that compare the weight and heights of average individuals, but it’s still a good way to get at least a general idea of how you’re doing in regards to weight and health.