What’s wrong with the BMI?

(Body Mass Index)

The BMI was first created in the early 19th Century by a mathematician named Adolphe Quetelet, who believed the average healthy weight for a person increased along with his or her height.

Thus was born the “Quetelet Index,” a basic formula designed to help people of all sizes determine if they were maintaining a healthy weight. With some slight variations and a name change (in 1972) to the “Body Mass Index,” Quetelet’s creation lives on today.

Although the vast majority of people use online BMI calculators, which require you simply to punch in your height and weight to calculate your BMI, the actual formula behind BMI exposes its biggest issue. The BMI formula is as follows:

Weight in Pounds x 703 Heights in Inches2

To spell it out, the BMI formula is your weight in pounds times 703 divided by your height in inches squared.

As you can see, BMI is based on two simple factors—height and weight. It takes no account of body-fat percentage, muscle mass, bone thickness or genetic predisposition to a certain frame.

BMI doesn’t take into account above-average amounts of lean muscle mass. It assumes everyone has the same percentage of lean tissue and fat tissue.  Therein lies the main problem with using BMI for athletes, body builders, or even people with above average musculature, or even genetically heavier frames than average.

However, even though this flaw in the BMI is well recognized, the measurement is still used in practically every doctors’ office to judge you as being overweight. Even worse, it is the measure that is used by many insurance companies to assess how much of a health risk you present!

The fittest, healthiest and leanest athletes, by that manner of thinking, present the greater health risk than a “normal” height/weight person who is unfit and actually carrying a lot more of the high risk tummy fat than the athlete – go figure! BMI does work – for the average person who is not fit, has no muscle tone and who has not done much weight bearing exercise that increases the density and strength of their bones.

What is your BMI? And does it really matter?

If you are an average person, the BMI calculation WILL have some meaning – it is s quick way to tell if your weight is average for your height! However, it cannot tell you if you are overweight, or if you carry weight in less healthy places (such as the visceral fat that makes a tummy pop out), or if you are more muscular than average, or if your bone structure is sturdy or too frail.

If you want to know if you are overweight – look in the mirror! How much does your tummy pop out (remember that some of the highest risk fat deposits are internal – you can’t grab them – but you can’t suck your tummy in to totally avoid looking at them either!)? How much adipose fat can you grab (adipose fat is the subcutaneous fat that you can grab under your skin)? What do you look like?

You tummy should be smaller than your chest, and what you can grab shouldn’t be more than about one centimeter thick (depending upon location and your build). But most of all you can SEE if you are overweight!

More reliable body fat percentage measurements

Skin Fold Calipers

Skin fold calipers measure subcutaneous fat (they cannot measure the visceral fat around your organs). Once you have the “skin fold” (thickness) of fat below the skin, a calculation is performed using population norms for age. As a raw measurement of how much fat is below the skin, skin fold calipers can help you track fat loss. However, due to the calculation of population averages, skin fold caliper methods lose their accuracy if your body type is not “average”.

Underwater Weighing (Hydrostatic Weighing)

You sit in a chair on a pulley system, breath out fully, and get weighed while submersed in a tank of water. The more dense your body, the heavier you are underwater – the more fat your body, the more you float.

You need to be comfortable holding your breath while underwater and not being in total control of when you can come back up! Apart from that, it is a reasonably accurate measurement of lean body mass. Variables include the amount of air left in your lungs (they usually measure your lung capacity and make a good estimation of how much are remains when you exhale fully), and the mathematics used to calculate lean body mass/fat mass.


A DEXA scan is a special type of X-ray that measures complete body make up. DEXA stands for “dual energy X-ray absorptiometry”. It is used to measure bone density, body fat percentage, and exactly what type of fat, and where it is deposited throughout the body.

Cenegenics uses the DEXA to get one of the most complete pictures of your body make up that is available. From here we can give highly accurate (and effective) programs of nutrition, supplementation, medication, exercise regime and general lifestyle guidance, so you can become the healthiest version of yourself. No confusion or guessing!

Find out more about our ELITE HEALTH EVALUATION here.