Monday Myths

Monday Myths – Why BMI Actually Got It All Wrong [3 Reasons Why]

Story Highlights
  • What is BMI?
  • 3 Reasons Why BMI Got it All Wrong
  • ShapeScale Works Where BMI fails

BMI charts are widely used by doctors and insurance companies as a standard determination of overall health. But how accurate is it really? The simple answer is that B.M.I is a flawed measure of health. This article highlight 3 reasons why BMI got it all wrong and how ShapeScale gets it right.

You are all probably familiar with BMI. Those three letters, which stand for body mass index, have become a proxy for whether a person is considered healthy.

What is BMI, exactly?

Part of its appeal is its simplicity of calculation. BMI measures a person’s height in relation to their weight. It is calculated by taking your weight in kilograms and divided by your height in meters squared. If it falls between 18.5 and 24.9, you’re at a healthy weight. Congratulations! Any number below that means you are underweight, and above the range means you are overweight. 30 or greater is clinically obese. Simple maths, right? Well, according to experts, including the person who invented it, BMI is a deeply flawed measure of health.

BMI Chart

BMI Doesn’t Tell You Much About Your State Of Health 

The researchers at UCLA analyzed the link between BMI and health markers like blood pressure and cholesterol levels. The study found that people were incorrectly categorized as obese. More than 30% of those with BMIs in the “normal” range (about 20.7 million people) were, in reality, unhealthy based on other health data. On the other hand, 15% of Americans (about 2 million people) who were classified as having a BMI of 35 or higher were actually healthy.

You might have exactly the same BMI as someone, but your bodies might look nothing alike. This is nicely illustrated in a photo below, published by the New York Times. It compares six people who are all 5-foot-9 and 172 pounds. All of them share the same BMI of 25.4, which is officially considered overweight. However, not a single body look the same. How is it possible that the same BMI can look so different?


We provide 3 key reasons why BMI is an incomplete representation of your health and why you should toss the BMI chart into the trash.

  1. It was never meant for individuals but to assess obesity of the general population
  2. Muscle and bone are denser than fat
  3. Fat Distribution Matters

reasons whybmi got it allwrong

It was never meant for individuals 

The BMI was first introduced in the early 19th century by a Belgian mathematician, Quetelet, who created the formula as a quick and easy way to assess the degree of obesity of the general population. In other words, it is a 200-years-old formula and hence very much outdated. Quetelet, as a statistician and not a doctor, explicitly stated at the time that the index should not be used to indicate the level of fatness in an individual. The formula works fairly accurately for a population study, where errors in large population regress back to the mean. This, however, does not hold on an individual basis. Nobody listened though. Due to its ease of use, this outdated formula becomes the norm for doctors to compare patients and insurance companies to evaluate members.

BMI does not differentiate between athletes and couch potatoes

The reason why the six people with the same BMI on the NYT photo above look completely different is that BMI doesn’t reveal anything about the makeup of your body. The huge failing in the current paradigm of focusing on weight is that BMI does not take body composition into consideration. The biggest downfall is that BMI does not take into account a person’s bone, muscle, or fat proportions. This is critical because muscle is much more dense than fat. Because BMI does not make a distinction between lean muscle and body fat, it fails to differentiate a muscle builder from a couch potato of the same height and weight.

For example, an individual with strong bones, good muscle tone and low fat is likely to have a higher BMI than someone who has a higher fat and lowers muscle tone. This is why athletes and other fit and health-conscious people often find themselves to be mistakenly classified as overweight or even obese even though they are in a better shape than an average person. For example, Tony Romo, an American football quarterback has a BMI of 29 which puts him well into the obese category. Technically “obese” means having an excess of fat. As BMI does not make a distinction between muscle, bone, fat or water, one can conclude it is an absurdly inaccurate measure of one’s fatness.

Fat vs Muscle

Take a look at the above image. As it states, each is an exact replication of 5 pounds of fat and muscle.

BMI Does Not Differentiate Between Apples And Pears

Another important point to consider is body fat distribution around the body. The real problems occur when fat accumulates around the waist. Yet body fat distribution is not under consideration when using BMI.

Body fat distribution varies among people. Some may be apple-shaped and carry most of their excess body fat around their stomach. Whilst others may be pear-shaped with most of their body fat around their hips, bum and thighs.  Studies show that the risk of dying and living with health complications is closely related to where a person carries his or her fat. When excess fat clusters around the midsection, it is more dangerous than when it is widely distributed.


Research published in the Annals of Internal Medicine has found that among adults aged 18 to 90 across the BMI continuum, having an apple shape increased the risk of death, particular death from cardiovascular disease. Interestingly, the study found that at BMI above 30, where obesity begins, both men and women with pear-shaped bodies were less likely to die than those with similar BMI who were apple-shaped.

Essentially, no matter how heavy a person is, the distribution of their body weight is a key predictor of health risk. BMI tells nothing about your body shape, which really makes you question how useful if at all, BMI really is.

It is embarrassing for doctors to be using this simple, outdated formula. Firstly, it was never meant for individuals. It does not make a distinction between body fat and lean muscle, nor does it consider body fat distribution. Overall it is an incomplete representation of one’s health and therefore it should not be used as a diagnostic tool.

Shapescale Is The Solution

Facebook Sharing

ShapeScale is a smart scale. It gives you complete measurements, weight, muscle and fat percentage all in one place. Where conventional scales only tell you your weight, ShapeScale differentiates between body fat and lean muscle. More, ShapeScale will tell you exactly where body fat is distributed using a heat map. ShapeScale does all the measurements for you so you no longer have to measure yourself manually which can be very tedious and prone to human error. Right now ShapeScale makes precise distance measurements up to a tenth of an inch making our product much more accurate than tape measurements.

Shape Index – A New Way To Measure Fat Better

Most importantly, ShapeScale will use the Shape Index which is a better and more reliable predictor of mortality than BMI. Unlike BMI, this new way of measuring body fat takes into consideration where the weight is concentrated. It combines BMI with waist circumference which determines the amount of belly fat a person has. As argued above, abdominal fat is a critical factor to take into consideration as it is linked to a number of health conditions. This makes Shape Index a more reliable predictor of health, as proven by a study published in the Journal of Translational Medicine. 

ShapeScale works where BMI fails

In other words, ShapeScale works in all the areas BMI fails. It does more than that. ShapeScale allows you to measure your fitness progress. While BMI can show some progress if you’re trying to lose weight, it is of very little use if you want to build muscle. You may be working out and eating right, yet you might see the numbers on the scale go up. You even may be moving up the BMI chart as heavier lean muscle replaces fat. This can be very discouraging. ShapeScale, on the other hand, creates a photo-realistic 3D model of you so you can visually track progress and detect changes the naked eye cannot see. Our scale will tell you exactly where your body is changing.

Do not hesitate, join the waitlist for the pre-order to get a true measure of your fitness.

Get the Ultimate Nutrition Guide
Use our free guide to design your very own personalized nutrition plan.
Download e-Book
Get the Ultimate Nutrition Guide
... start working on your unique diet plan.
Download E-Book

Wiktoria Banda

Wiktoria is a content writer and illustrator at Shape.
Get the Ultimate Nutrition Guide
Use our free guide to design your very own personalized nutrition plan.
Download e-Book
Get the Ultimate Nutrition Guide
... start working on your unique diet plan.
Download E-Book