BMI Chart: Why It's A Bad Idea To Trust It

It's incapable of measuring the most important health markers.
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Imagine blindfolding someone who’s never seen you before and then asking them to tell you if you’re too skinny or too fat.

Would you trust their answer?

Probably not.

The BMI Chart, also known as the Body Mass Index Chart, is about as reliable as the aforementioned blind person when it comes to measuring your state of health.

Yet it’s a tool that’s commonly used in North America to determine whether or not a person is obese, proportioned or underweight for their height.

How Does The BMI Chart Work?

<a href="" target="_blank" role="link" rel="nofollow" class=" js-entry-link cet-external-link" data-vars-item-name="Body Mass Index (BMI) Chart" data-vars-item-type="text" data-vars-unit-name="57c0d013e4b0b01630df147a" data-vars-unit-type="buzz_body" data-vars-target-content-id="" data-vars-target-content-type="url" data-vars-type="web_external_link" data-vars-subunit-name="article_body" data-vars-subunit-type="component" data-vars-position-in-subunit="0">Body Mass Index (BMI) Chart</a>
National Heart, Lung, and Blood Institute
Body Mass Index (BMI) Chart

The BMI chart claims to accurately determine the healthy weight of an individual by dividing a person’s height by their weight. This formula calculates what’s called your BMI score, and is then measured on a chart that instantly classifies you as underweight, normal or obese.

Here’s the Body Mass Index formula:

Height in centimeters ÷ Weight in kilograms = BMI

The BMI formula was developed in the 1830s by Lambert Adolphe Jacques Quetelet, a Belgian astronomer, mathematician and sociologist. It was believed to be an accurate measure of body fat percentage because it assumed that for most people, their weight and height correlate with the amount of fat mass they have.

But the BMI chart fails to consider a few crucial points, which are necessary to accurately determine a person’s state of health.

Why The BMI Chart Is Flawed

The BMI Chart's Biggest Flaw: It Doesn't Consider Muscle Mass
The BMI Chart's Biggest Flaw: It Doesn't Consider Muscle Mass

One of the biggest flaws with the BMI chart is that it fails to take muscle mass into consideration.

Instead, the BMI formula calculates a percentage of your body weight which could be muscle or fat. And while excess fat mass is an indicator of obesity and a slow metabolism, lean muscle mass is an indicator of good health and a faster metabolism.

And since both muscle mass and fat weigh roughly the same, there’s no way for the BMI chart to distinguish between the two.

As you can guess, a high BMI doesn’t necessarily mean that you’re overweight or have excess body fat. For example, a bodybuilder who has a low body fat percentage but weighs 200 pounds at 5’9” is still be classified as overweight according to the BMI chart.

The BMI chart doesn’t consider where fat mass is distributed. While visceral, or abdominal fat gain is linked to an increased risk for developing cardiovascular disease and Type 2 diabetes, evenly distributed weight gain is said to be less of a risk for metabolic conditions (1).

And since the BMI chart doesn’t consider where fat mass is concentrated, a person could actually be at risk for heart disease and metabolic conditions associated with obesity, despite having a “healthy” BMI.

And finally, the BMI chart doesn’t look for other important health markers, such as chronic inflammation— which is at the root cause of all illness and disease and contributes to obesity (2).

Interestingly enough, when Quetelet came up with the BMI, it wasn’t meant to measure fat mass. Instead, it was invented to measure the average build of a male in his era (3).

So, if you’ve ever received a seemingly unfair or disappointing BMI score, now you know the truth: the BMI chart is incapable of measuring the most important health markers.

Better Measures of Body Shape

A Better Measure of Body Shape: Your Whole Food Consumption
A Better Measure of Body Shape: Your Whole Food Consumption

Instead, you’re better off measuring your health by paying attention to how many fresh, whole foods you’re eating on a daily basis, if your clothes are fitting comfortably, how much sleep you’re getting each night, and how you’re managing your stress levels.

Unlike the BMI chart, your diet and lifestyle habits never fail to tell the whole story.

Measuring your lean muscle mass percentage can also give a better picture of your current state of health. This is because higher lean muscle mass is linked to a faster metabolism, stronger bone health and a greater caloric expenditure throughout the day ― which results in greater fat loss.

In order to calculate your lean body mass (LBM) percentage, you can use an LMB calculator online.

But first, you’ll need to know your body fat percentage, which can be measured using a skin caliper, found on Amazon for under $5. The LBM calculator will ask you to enter your weight in pounds or kilograms, as well as your body fat percentage, to determine your LBM score.

As suggested above, it’s always best to get a clear picture of your entire body composition, rather than trusting a number that makes a vague statement about your health.