BMI doesn't indicate health.
4 Reasons Why BMI Is Inaccurate, and What To Use Instead


Full disclosure – the original title of this blog was 4 Reasons Why BMI Is Bullsh**. Because it is. The BMI is inaccurate, highly flawed, and has no business in a nutritionist’s office. 

At Ancora Wellness, our mission is to provide holistic support for your total wellness. Spoiler: that does NOT include looking at your BMI. But it does include offering many integrative services such as naturopathic care, nutrition support, mental health counseling, and energy work. Connect with us today to learn more and book your appointment.

What Is the BMI?

When you go to a medical provider, they often take your height, weight, and other measurements like blood pressure and pulse. Some providers also calculate your height and weight to create a ratio called the Body Mass Index, or BMI. Based on this ratio, they place you into a category such as underweight, normal weight, overweight, or obese.

Medical professionals and insurance actuaries have used this information to make snap determinations about a person’s supposed level of health. And honestly, it’s almost hard to know where to start when discussing how flawed and messed up this system is. But I’ll try.

The BMI Is Inaccurate for So. Many. Reasons.

The BMI is inaccurate and flawed.

This ratio has been in use since the 1830s and has been problematic since the beginning. Here are the top four reasons why BMI is inaccurate and flawed.

1. BMI is an arbitrary ratio with no basis in medicine.

A Belgian man named Lambert Adolphe Jacques Quetelet invented the ratio in the 19th century, calling it The Quetelet Index. But here’s the thing. He was a sociologist and a statistician, not a doctor or any other type of medical professional. He had no medical expertise whatsoever.

Quetelet’s goal was to define “the average man,” and he used this formula to determine the average-sized man in multiple countries to compare them to each other. His data collection included almost exclusively white men from the 1800s. He admitted that the formula was designed to compare populations and not individuals. 

In 1972, the name switched to BMI. Regardless of what we call it, there is no physiological significance to the square of your height compared to your weight. The formula is simply a mathematical attempt at defining the average-sized body.

Your level of health does not relate exclusively to your BMI.

The creator of the BMI explicitly said that the formula was not designed to determine fatness in an individual. This ratio was shelved and unused for a long time until life insurance companies were looking for a data point to determine policy rates. They started to collect BMI information, although it was largely self-reported. 

Do you want to guess how accurate our self-reported BMI usually is? Hint: not at all. Even though this formula has no basis in medicine and had flawed data collection, physicians in the 1950s started using it as an indicator of health. BMI is inaccurate and has been from the start.

2. BMI doesn’t take into account body composition.

One of the problems with using BMI as an indicator of health is that it doesn’t account for body composition, age, gender, or ethnicity. Because of its one-size-fits-all formula, the BMI ignores all of the following:

  • Men and women have different percentages of fat and muscle. 
  • Bone density differs from person to person.
  • Body composition changes with age. 
BMI doesn't account for body composition, gender, or age.

The formula provides skewed data that categorizes more tall people as overweight and shorter people as underweight. Athletes are almost always in the overweight or obese category, even if they are in peak physical shape. And since BMI was based on white men, it is not as accurate for people of color. BMI often overestimates fatness in the Black population and underestimates risk in Asians. 

3. BMI creates a flawed definition of obesity and often leads to discrimination. 

By the 1980s, the National Institutes of Health (NIH) started using BMI to define obesity. The threshold for a person to be considered obese is an arbitrary number based on a flawed mathematical formula, and this definition has changed over time. 

It also gives very narrow thresholds for its categories, meaning that a person could gain or lose just a few pounds and change categories of “health.” The BMI categories do not rely on any medical diagnostic criteria or symptoms. And yet, the medical community uses BMI to diagnose obesity as a disease. 

BMI is inaccurate because it was based on white men.

Unfortunately, this determination also allows medical institutions to use BMI to exclude people from medical treatment. 

  • If a person’s BMI is too high, providers may deny surgeries of all types. 
  • Doctors may ask transgender patients to lower their BMI before providing gender-affirming care. 
  • Before the Affordable Care Act, insurance companies could refuse to insure someone for being obese by BMI standards even if they had no other underlying medical conditions.

4. Obesity has become a synonym for unhealthy. 

There truly isn’t enough research to conclude that obesity always means unhealthy. At best, we can draw correlational conclusions about body size and risk for disease. Simply stated, there is no disease caused by fatness or your height-to-weight ratio. 

I want to introduce you to the obesity-mortality paradox. This paradox refers to research that shows those in larger bodies have increased longevity compared to those in smaller bodies. This same paradox also points out that health outcomes are often poorer after weight loss for many diseases. 

A 2016 study found that 30% of people with a “normal” BMI had other metabolic measures that indicated disease. So relying on BMI as a measure of health fails for almost a third of “normal” weight folks. 

Your BMI does not indicate your metabolic health.

The same study found that 47% of “overweight” people and 30% of “obese” people had no metabolic labs out of range. These folks may experience shaming by their medical providers or society at large for being unhealthy just because they have larger bodies when they are indeed healthy. Body size, BMI, and weight are only a part of the picture.

What I Look at Instead of the Flawed BMI

So if BMI is inaccurate and flawed, how can nutrition and medical experts determine health levels? So glad you asked!

When folks come to me in my nutrition practice, I explore many aspects of diet that do not include weight. Some of the food and habit changes we make together may lead to weight shifts, either gain or loss. Most of the time, these changes are short-term. 

Here are some ways I work with clients without any regard for BMI.

Diet and Lifestyle Shifts

My goal is to advise diet and lifestyle modifications that will improve your whole-body health, even if they do not affect your weight. Some of these changes include:

  • Eating more vegetables
  • Increasing your fiber intake
  • Paying attention to daily movement
  • Eating predictable and regular meals 

Labwork Data

Labs give us a much better picture of our health than BMI does.

Labwork presents me with additional health measures like cholesterol levels, blood sugar, and vitamin or mineral deficiencies. It’s also essential that I check in with my clients about any diagnoses they have. Some conditions can impact how their body interacts with food, so we need to make necessary adjustments. 

Deep Dive Into Nutrients

Because BMI is inaccurate, it’s important to examine a person’s nutritional intake when determining treatment plans. By taking an in-depth look at what a client is eating, I can see if there are gaps in macro- or micronutrients that we need to address and if there are opportunities to diversify the foods they eat.

I also consider if they are taking any medications that cause nutrient deficiencies. For example, gender-affirming hormone therapies may affect health, and we can make adjustments to balance those challenges.

Emotional Side of Eating

For the best long-term results, I definitely take into account a person’s relationship with food. Most of the time, difficulties can stem not only from what a person eats but also how and when they eat.  

Emotional and lifestyle issues are more important to examine than BMI.
  • Do they skip meals throughout the day and then feel insatiable when they do make time to eat? 
  • Do they label foods as good or bad and extend this morality to themselves when eating those foods? 
  • Do they have other coping mechanisms in place besides food? 
  • Is food a place to escape hard feelings? 
  • Is the person used to feeling uncomfortable in their body (due to anxiety, depression, or neurodivergence, among many other things), and hunger and fullness are just other feelings they tend to ignore? 
  • Do they have sources of joy and nurturing aside from food? 
  • Have they experienced food insecurity? 
  • Do they have fears around food?

BMI can’t give us any of that juicy information and can sometimes be a barrier in the conversation. But the mental and emotional sides of eating habits are very impactful and deserve attention. 

Handling a Doctor’s Office Weigh-In

Most of us have been trained to believe that a doctor visit must include the scale. But it doesn’t have to be. You can decline to be weighed and ask your provider to consider other measurements instead. 

You can ask your doctor to skip your weight check.

Admittedly, it can feel intimidating to advocate for yourself in this way, so try one of these statements:

  • “I am not using weight as a way to navigate and understand my health. I would like this visit to focus on my wellness and overall health independent from weight.” 
  • “I’ve learned that too much focus on my weight is harmful to my health, and I no longer weigh myself. I’d like to continue this approach with you during this visit as well.”

Sometimes, checking your weight is a legitimate need for your care and treatment. In those instances, you can say, “If weighing me is medically necessary to inform treatment and care, I’d prefer not to see the scale number. Please make sure you and your staff do not communicate this number to me at all throughout my visit, including on my end-of-appointment paperwork.” 

Nutrition as Part of Your Holistic Care

The Ancora Wellness providers function as a team to offer you an integrative form of healthcare. We work collaboratively to support your best health. To that end, our services complement each other beautifully.

Holistic and integrative care is crucial to your overall health.

For example, my nutrition clients may also benefit from counseling to unpack their experiences around food. Or they may work with our ND to address underlying physical conditions. Our goal is to support you as holistically as possible under one roof. And we never require a diagnosis in order to treat you. 

We invite you to connect with us today to learn more and to schedule an appointment with our team.

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