Body Max Index or BMI as it is more commonly called, is a value derived from the mass (weight) and height of an individual (body mass divided by the square of the body height), and is an attempt to calculate the amount of tissue mass (muscle, fat, and bone) in an individual, and then categorize that person as underweight, normal weight, overweight, or obese based on that value.
Using me as an example, (I’m old school so I did it in Imperial measurements), I am currently overweight according to this BMI calculator, with a BMI value of 25.8:
(I’ve embedded a calculator at the end of this post if you’d like to find out your BMI also.)
However, there are criticisms of using the BMI to define obesity in individuals, one of which being that BMI was designed for population studies, not individuals. Let’s check out these charts.
When comparing these women on the chart, you can see their torsos are all shaped differently.
The six body scans in this chart are of men who were all 5 feet 9 inches tall and 172 pounds, with a BMI at 25.4, which technically, could be considered overweight according to the Centers for Disease Control and Prevention (CDC).
These illustrations were created from scans of real people by New York City based startup Body Labs, which creates 3-D body models to help companies create clothing and other wearable products that fit just right. For each person the number labeled V is their body’s volume, or the amount of fluid that would fill a container the same size as their body, in liters. | The New York Times | Credit BodyLabs
So you’re probably wondering how is it they can all look so different even though they all have a similar BMI value?Simple. Muscle and bone are heavier than fat and some people carry more or less weight in their torso or legs. As BMI factors in only height and weight, it fails to incorporate these differences.
As a matter of fact, body fat percentage (BFP) is a more reliable indicator of obesity than BMI: very muscular, lean (low body fat) individuals can be classified as obese using BMI, but are classified as having a normal weight using BFP. An even simpler alternative to the BMI is to define obese individuals as those whose waist circumference is greater than 50% of their height, indicating excess intra-abdominal fat.
Oh well, all is not lost. I redid my calculations in metric, and all of a sudden I was ‘normal’ which just goes to show, not only can’t you rely solely on BMI to calculate your health, but you can’t rely on the calculator itself! 😉
Time for a snack!