BMI And Health: What Your BMI Actually Tells You
Trigger warning - due to the topic, the ‘O’ words are used.
I do not support the use of these words in healthcare and acknowledge that they can be harmful.
The Body Mass Index, or BMI, is a nutrition concept that we have been taught to accept without questioning.
And in a big way.
BMI is often used to determine if we are healthy or not.
It is used to label bodies with titles like “normal,” “overweight” and “obese.” And may even determine access to certain procedures or surgeries.
But should it have this much power?
Let’s take a closer look together and see what you think.
What is the BMI actually?
The BMI is an equation. It is a person’s weight in kilograms divided by their height in meters squared. It was actually first called the Quetelet Index when Adolphe Quetelet developed the formula in the 1830’s-1850’s.
Quetelet was an astronomer, mathematician, statistician and socialist (aka…not a healthcare provider) and he had a fascination with studying the average man and developed the BMI as a way to discover the socially ideal person.
So the BMI was originally created to study the white European male of the mid 1800s and Quetelet never intended the BMI equation to determine anything medically about anybody…not even the white European male of the 1800s.
Fast forward many, many years, to 1972 when Ancel Keys and others resurfaced this equation and renamed the Quetelet Index the BMI for the purpose of determining relative obesity. Ancel Keys acknowledged that the BMI could be used for population studies, but was not appropriate for individual evaluation.
And to this very day, the BMI has still not been validated as a tool to use for individual assessment.
What does this mean?
Usually when we want a test or equation to help us determine something about someone, we experiment with that test or equation to make sure that most of the time it is telling us the information about the person we want to know.
In other words - does it actually work? Take a test for ADHD for example. We need to know that it is actually correctly diagnosing people for ADHD first. Bob down the street can’t just create 5 questions that he thinks will work and then we all start using that to diagnose our kids. We need to test Bob’s 5 questions first, thoroughly and repeatedly, to see if MOST of the time, Bob’s 5 questions actually result in a true ADHD diagnosis.
The BMI has never been tested and proven to determine the health of an individual person or even the “fatness” of an individual person's body.
BMI has been studied extensively, it is a simple and inexpensive tool to study trends in populations. But that is different from saying that BMI has been validated as an individual health assessment tool.
As a matter of fact, the BMI has been proven to misclassify people as healthy and unhealthy (more studies included below under BMI profiling).
And yet…we use it on the regular in healthcare in the United States for individual health assessment even though more medical communities are acknowledging not only its limitations but also its ability to harm.
Why?
Because it is easy.
I also suspect our continued desire to classify bodies as good or bad also plays a role as well as racism.
But you will most often hear that the ease of using the equation is the reason it continues to be used…even though an easy-to-use tool isn't necessarily an accurate tool for the job we're asking it to do.
The Problem With Using The BMI
There are a couple of problems with using the BMI for individual assessment even above and beyond the fact that it is just often just wrong.
One is what we call BMI profiling.
BMI profiling means that in a healthcare setting someone may be considered healthy because they have a “normal” BMI and that someone is unhealthy because they have BMI that is classified as either “overweight” or “obese.”
The problem here is that people that have BMI’s may be told that they are unhealthy and that may not be true (also here, and here, ), they may be very healthy when looking at other indicators such as lab values, blood pressure, activity level, nutrition, sleep, stress management, and mental health.
Likewise, a person that falls into the “normal” BMI category may be told that they are healthy but they are not based on other indicators as well such as nutrition, activity level, sleep, stress management and mental health. We just assume these things are going well enough because that person is thinner and they miss treatment.
Both scenarios are problematic.
Both body types can be underserved by using the BMI as a health indicator.
Focusing on BMI as a determinant of health can also cause healthcare providers to assume the solution to everything from joint pain to sleep apnea to diabetes can be resolved if someone were to just lose weight.
This can lead to a tunnel vision that can prevent someone at a higher BMI receiving additional recommendations or even diagnostic tests.
There is not one disease that only shows up in people who are fat.
There are other recommendations being made to people with “normal” BMI’s who experience joint pain, sleep apnea and diabetes that aren’t being offered to the patient who “just needs to lose weight?”
Barrier to Healthcare
This also often creates a barrier for individuals when it comes to engaging with healthcare. I can’t tell you how many people have told me that they put off their annual physical or avoid seeing the doctor as much as they can so they don’t have to have “the weight conversation.”
And I get it.
If every visit turns into a conversation about the number on the scale, it can be really hard to feel like your healthcare provider is actually listening to you.
You may have come in because you're exhausted.
Or having trouble sleeping.
Or experiencing back or joint pain.
Or dealing with digestive issues.
Or noticing changes in your blood sugar.
And instead of talking about those things, the conversation becomes:
“You really should lose some weight.”
That can make people feel dismissed.
And when people feel dismissed, they may stop going to the doctor.
That isn't a great recipe for better health.
Psychological Implications
And lastly, there is a lot of shame that many people experience when they are given the labels “overweight” or “obese.”
This shame can result in psychological harm. More simply said, when we feel ashamed, we don’t tend to show up in life as our full selves. We can experience negative self-talk and may not pursue relationships, activities, roles, and even health promoting behaviors because of the way we feel about ourselves.
I see this often in my practice.
When we believe there is something inherently wrong with our bodies, it can change the way we move through the world.
We may avoid relationships.
We may avoid activities we enjoy.
We may stop going to the beach or the pool.
We may put off buying clothes that actually fit our bodies.
We may avoid medical care.
We may spend enormous amounts of time thinking about food and our bodies.
And we may become so focused on changing our bodies that we lose sight of actually taking care of them.
Shame is a terrible long-term motivator.
When we believe that we are inherently “bad,” we can begin to believe that our behaviors are bad, too.
And that can get in the way of taking care of ourselves in the ways that actually support our health.
Where Do We Go From Here?
If you find this information compelling you might be wondering where to go from here. Even if the BMI has significant limitations, it is still commonly used in our healthcare system in the U.S.
You can start by deciding that the BMI is not the definition of your health.
You can think through other factors that help you determine how your body is doing such as:
Sleep
Stress management
Nutrition
Movement
Medication compliance,
Mental health
Blood pressure
Blood sugar
Cholesterol and other labs
Symptoms
Your own experience of your body and health
It also can be helpful to ask your healthcare provider to look at the whole picture with you.
If your doctor is recommending weight loss based on your BMI, you can consider asking if they have any additional recommendations. This can sound like:
“I hear you that you believe weight loss will be beneficial and I will keep that in mind. Do you have any other recommendations for me? What would you recommend to someone with __________ who you did not believe needed to lose weight?”
Because we know that high cholesterol, high blood pressure, type 2 diabetes, sleep apnea, etc happen in all sized bodies, this may help your provider think beyond weight and offer you more solutions or further investigation.
Even if you decide weight loss is something you personally want to pursue, this can be a valuable conversation for taking care of your overall health and making sure you are being diagnosed and treated appropriately.
Want to Learn More?
If you've experienced shame or frustration around BMI and healthcare, you don't have to work through it alone.
Working with a weight-inclusive or HAES®-informed registered dietitian and/or therapist can be one place to start.
A couple of resources I like:
Weight and Health Care Substack by Reagan Chastain
“The Racist Roots of Diet Culture” Food Psych Podcast with Dr. Sabrina Strings
Food Isn’t Medicine by Dr. Joshua Woolrich M.D.
And, of course, you can always start by having a conversation with your own healthcare provider.
You are allowed to ask questions.
You are allowed to ask for more information.