Body Mass Index, or BMI, is one of those health numbers that tends to make people frustrated—especially people who strength train.

If you’ve ever lifted weights consistently, gained muscle, improved your health markers, and still been told that your BMI puts you in the “overweight” or “obese” category, you’re not alone. This comes up often with clients, especially adults who train hard and carry more muscle than the average person.

So what exactly is the Body Mass Index? Find out in the video below, or you can read the accompanying blog post if you don’t feel like sitting and watching.

CHAPTERS:
00:00 Introduction
00:35 What is Body Mass Index?
01:23 Origins of Body Mass Index
05:12 Limitations of Body Mass Index
07:07 Body Mass Index vs. Body Fat Percentage
07:34 Why Do Doctors and Insurance Companies Use Body Mass Index?
08:51 Why Should We Care About Body Mass Index?

Your body mass index, or BMI, is simply a ratio of your body weight to your height squared. In the metric system, it is calculated using your weight in kilograms divided by your height in meters squared. In the imperial system, the equation uses a conversion factor of 703 to adjust for pounds and inches.

That’s it.

BMI is not a direct measurement of body fat. It is not a body composition test. It does not know how much muscle you have, how strong you are, how active you are, or what your blood work looks like. It is just a number based on height and weight.

For adults, height generally stays the same, while weight can change. That means your BMI changes when your body weight changes, but it does not explain why your weight changed.

Did you gain fat? Did you gain muscle? Did you lose muscle? Did you retain water? BMI does not know.

And that is where the problem begins.

Where Did BMI Come From?

The Body Mass Index has a long history, and it was not originally created as a modern medical screening tool.

The concept came from Adolphe Quetelet, a Belgian statistician and sociologist in the 1800s. Quetelet was interested in what he called “social physics,” which was essentially the use of statistical analysis to understand trends in human populations.

That is important.

The Body Mass Index was created from population data. It was not designed to diagnose the health of an individual person. It was never meant to look at one strength-trained adult, one athlete, one parent, one busy professional, or one person walking into a gym in West Hartford and determine whether they were healthy.

It was a broad statistical tool.

Later, in 1972, Ancel Keys helped popularize the term “Body Mass Index.” Keys concluded that BMI was a reasonably useful relative weight index when looking at groups of people. But even then, the key idea was population-level analysis—not individual diagnosis.

That distinction matters.

BMI can be useful when you are looking at large groups. It becomes much less precise when you apply it to one individual person.

Why BMI Frustrates People Who Strength Train

If you strength train, BMI can be misleading.

That is because muscle adds body weight. A person who carries more lean mass may weigh more for their height, which can push their BMI into a higher category—even if their body fat percentage, blood pressure, blood work, fitness level, and lifestyle habits are all healthy.

This is why so many lifters, athletes, former athletes, and strength-focused adults dislike BMI. It can make a strong, capable, healthy person look unhealthy on paper.

For example, someone may be classified as “obese” by BMI while having a healthy body fat percentage and excellent health markers. That does not mean BMI is accurately describing their health. It means BMI is doing what BMI does: comparing height and weight without context.

It does not factor in:

• Muscle mass
• Body fat percentage
• Waist circumference
• Training history
• Cardiorespiratory fitness
• Blood pressure
• Cholesterol
• Glucose markers
• Lifestyle habits
• Injury history
• Strength levels

That is a lot of missing information.

At Viking Athletics in West Hartford, we care much more about the full picture. If someone is getting stronger, building muscle, improving conditioning, moving better, feeling better, and improving their health markers, that matters far more than one isolated number.

Does That Mean BMI Is Useless?

No. BMI is limited, but it is not completely meaningless.

It can still be a useful screening tool. If someone has a high BMI, that may be a reason to look deeper. It may prompt a conversation about body composition, cardiovascular health, nutrition, sleep, blood pressure, or metabolic markers.

The mistake is treating BMI as the whole story.

BMI can tell us, “This person has a higher body weight relative to height.”
It cannot tell us, “This person is healthy or unhealthy.”

That is the difference.

A better approach is to pair BMI with other measurements, such as:

• Body fat percentage
• Waist circumference
• Resting heart rate
• Blood pressure
• Blood work
• Strength levels
• Conditioning capacity
• Daily movement
• Nutrition habits
• Sleep and recovery

For an individual, especially someone who strength trains, body composition is often far more useful than BMI alone.

Why Do Doctors and Insurance Companies Still Use BMI?

The simple answer is that BMI is easy.

It is fast, inexpensive, and requires only height and weight. That makes it convenient for large healthcare systems, insurance companies, and population-level risk assessments.

Insurance companies are in the business of evaluating risk across large groups of people. They rely heavily on statistical models, and BMI fits neatly into that kind of analysis.

But what works for a population does not always work perfectly for a person.

This is why someone can have great blood work, a strong training history, a healthy body fat percentage, and still be penalized by an insurance classification because their BMI is “too high.”

Is that frustrating? Absolutely.

But understanding why BMI is used can help you keep it in perspective.

Why Higher Body Mass Still Matters

Here is the part that strength-trained people sometimes do not want to hear: even if your high BMI comes from muscle, you still need to care about cardiovascular health.

Your heart has to support the body you have.

Whether your body mass comes from muscle, fat, or a combination of both, a larger body places greater demand on the cardiovascular system. This does not mean muscle is bad. It means that if you are carrying a lot of mass, you should not ignore your conditioning.

This is especially important for strength athletes, bodybuilders, powerlifters, and anyone who prioritizes lifting over cardio.

You still need aerobic work.

You still need to train your heart.

You still need to build and maintain cardiovascular fitness.

At Viking Athletics, we believe strength training is essential—but strength should not come at the expense of heart health. The goal is not just to lift more weight. The goal is to build a strong, capable, resilient body that can perform well for years.

That means your training program should include both strength and conditioning.

What Should You Track Instead of BMI Alone?

If you want a clearer picture of your health and progress, do not rely only on BMI. Use it as one data point, not the final verdict.

Better markers to track include:

1. Body Composition

Body composition helps separate lean mass from fat mass. This gives you a better idea of what is actually changing when your weight changes.

2. Waist Measurement

Waist circumference can provide useful information about abdominal fat and health risk.

3. Strength Progress

Are you getting stronger over time? Can you lift, carry, squat, hinge, push, and pull with more control and confidence?

4. Conditioning

Can you recover between sets? Can you walk, hike, row, bike, or climb stairs without feeling completely drained?

5. Blood Work and Blood Pressure

These give insight into what is happening internally and should be discussed with your healthcare provider.

6. How You Feel and Function

Energy, sleep, pain levels, mood, confidence, and daily performance all matter.

The scale and BMI chart are not useless, but they are incomplete.

The Bottom Line on BMI

BMI is not the enemy. It is also not the whole truth.

It is a simple screening tool based on height and weight. It can be useful for looking at trends across populations, but it has major limitations when applied to individuals—especially people who strength train.

If your BMI is high, do not panic. Look deeper.

Ask better questions:

• What is my body fat percentage?
• How is my blood pressure?
• How is my blood work?
• Am I doing enough cardio?
• Am I strong?
• Am I mobile?
• Am I recovering well?
• Am I building a body that supports the life I want?

For strength-trained adults, the goal is not to chase the lowest possible BMI. The goal is to build muscle, reduce unnecessary fat, improve conditioning, protect your heart, and create a body that is strong, healthy, and durable.

If you are in West Hartford, CT and want help building a smarter training program that balances strength, conditioning, and long-term health, Viking Athletics can help.

Ready to Train Smarter?

Book a free No-Sweat Intro at Viking Athletics in West Hartford, CT. We will help you understand where you are now, what numbers actually matter, and how to build a training plan that fits your body, your goals, and your life.