Is BMI accurate? Debunking the myths of one-size-fits-all fitness

Fitness & Sports Health

by Gillian Koskie

Mar 19, 2024

Body mass index, or BMI, has long been used as a metric for assessing wellness and fitness. But many experts are now seeing its limitations, arguing that this calculator is an inaccurate way to measure if someone is healthy or not.

As more and more fitness professionals focus on a holistic approach to weight management, the bottom line is that using BMI as a calculator for wellness doesn’t work and isn't inclusive. Let’s find out more.

How BMI is measured

BMI is used to estimate your body fat based on your height and weight, which can then indicate fitness level and overall health. It’s calculated by dividing weight in kilograms by height in meters squared.

After calculating your BMI, you can correlate your number to the BMI scale to see if you fall in the underweight, normal weight, overweight or obese category.

Why is BMI flawed?

BMI is not considered a trustworthy measure of body fat percentage or fitness level anymore because it only considers height and overall weight, but there are many other variables that make up a person’s weight.

For example, two people could have the same BMI but look different and perform physically at opposite levels. Someone who has a large amount of muscle may weigh the same as someone who is overweight, thus placing them in the same BMI category, which is inaccurate.

BMI and body fat percentage

One of the key issues with the BMI scale is that it doesn’t allow for differentiation between the types of fat:

  • Essential body fat is the minimum amount of fat needed by the body’s various systems to support basic life function.
  • Visceral fat is stored in our abdomen and is what surrounds our vital organs and is necessary for survival.
  • Subcutaneous fat is stored under the skin. Abnormal amounts of subcutaneous fat contribute to obesity, yet the BMI equation does not consider this specification.

There are other factors such as bone density and water retention that also contribute to your weight but do not necessarily mean you are overweight or unhealthy.

What to use instead of BMI

There are other more accurate and specific ways to assess body fat, one of those being the skinfold caliper method. This involves using medical calipers (a measuring tool) to understand the thickness of skinfolds on different parts of your body, including the abdomen and under the arms.

This helps calculate the amount of subcutaneous fat, which is a more accurate correlation to fitness level and overall health compared to the BMI scale.

There are also various fitness assessments a licensed professional can take you through to determine your fitness capacity, such as measuring your overall upper and lower body strength by seeing how much weight you can lift.

The results of the skinfold test and fitness tests can together provide the most accurate and well-rounded insight into your overall health and fitness.

Moving beyond the BMI scale

The fitness industry is evolving away from the idea of having a “perfect body” and toward the idea that fitness is for everyone. If you’ve recently gone to a group exercise class, you may have heard a few phrases such as “listen to your body” or “do what works best for you.”

This is because we are more focused on providing modifications and options to people exercising so that no matter what age, size, gender or fitness level you are, you can find confidence and motivation through moving your body, whatever that looks like for you.

Exercise is no longer a “one-size-fits-all” environment—and that’s a really good thing.

Connect with an expert today to reach your fitness goals.


About the Author

Gillian Koskie is an exercise physiologist at Baylor Scott & White All Saints Medical Center — Fort Worth.

We make it easy.

Healthcare doesn't have to be difficult. We're constantly finding ways to make it easy so that you can get Better and stay that way.

Better tools make it easier

We all have different healthcare needs. Handle them your way with the MyBSWHealth app. Download the app today and take a hands-on approach to your healthcare.

Text Better to 88408