Breaking Down BMI

As a former nutrition student, part of my curriculum was to become familiar with different means of body measurements. These range from simple height and weight, to a super expensive space-ship look alike machine that measures air movement through the body called the “BOD POD”. 

If you haven’t already guessed, machines like this one are super expensive, which is why most people haven’t heard of it. It’s not likely that any of us will walk into the doctor’s office and see a Bod Pod waiting for us. This very reason is why most people are familiar with a much simpler body measurement method- BMI. 

For those who don’t know, “BMI” stands for “Body Mass Index”, and is a numerical value of a person’s weight in relation to their height and is determined using an equation. It is used to broadly categorize an individual as being one of the following: “underweight” “normal” “overweight” or “obese”. BMI isn’t perfect. In fact, it can be quite misleading in some circumstances. 

Side note: I won’t be providing the calculation or the reference values in this post; so if you’re intimidated by weight status labels, don’t stress! If you are interested in calculating your own BMI, there are plenty of BMI calculators on the internet! 

I want to be clear, it’s not that I have beef with BMI. In fact, I think it can be a useful and inexpensive tool to help determine someone’s weight/health status. However, I do think it’s fair and responsible to criticize BMI as a measurement, and that’s exactly what I’m going to do!

Today, I’ll be breaking down why BMI is an imperfect indicator of health/weight status, some flaws within the measurement itself, and how it can be used responsibly with other tools to give a more accurate overall picture of a person’s health. 

Body Composition

My biggest critique of BMI is that it does not take a person’s body composition into account. For example, one liter of muscle weighs 2.30 pounds, while one liter of fat weighs 1.98 pounds. This means that people with more muscle and less fat such as athletes and those who exercise often could show higher BMI scores than those with less muscle and more fat. Additionally, individuals (especially women) are built completely different from one another. Why should short and curvy women be measured with the same method as long and lean women when their distribution and presence of natural fat is so unalike?

No Quality of Life Indicators

One method that was commonly used in my undergraduate classes to help determine a person’s health was “quality of life”. Simply put, how is a person feeling? Can they go on walks with their friends and eat at restaurants without any digestive issues afterward? Questions like this that aren’t so “science-based” matter, because they provide insight as to how “normal” of a life people can live. A person with an “overweight” BMI might be able to go about their day with no problems. Look at Lizzo! She’s singing, dancing, and playing the flute onstage, which requires major cardiovascular endurance. As a large woman, it appears that she can live the life she wants with no visible problems.

Too broad 

Honestly, BMI just isn’t specific enough. The fact that one pound can categorize someone as having an “underweight” or “normal weight” body is so extreme and kind of ridiculous when you think about it. It also has the potential to be dangerous. If a patient with disordered eating patterns is in the “normal weight” range, their condition might go unnoticed or not receive the attention and care needed. Despite being in what is perceived to be a “healthy” weight, deeply unhealthy and detrimental behaviors and body changes could be occurring.  

Not Developed by a Medical Professional  

It was developed by a Mathematician. Yes, math people are smart and needed. But they aren’t qualified to be giving means to measure weight status. Case closed.

So how can BMI be used responsibly to give a more accurate representation of someone’s health? Glad you asked!

Take all Health Attributes into Account 

For starters, BMI alone cannot be used to determine someone’s health and weight status. Tests for attributes of health like blood sugar levels, cholesterol, kidney function, blood pressure and others should be taken into account. These conditions are often related to a person’s weight status, so they might offer a more accurate depiction. 

Family History 

Family history of diseases and conditions is also incredibly important. I have a “normal weight” BMI, yet I know that I might have to watch my cholesterol due to a family history of unbalanced levels. Genetics are real, y’all, and they’re a major player in health status.

Other Measurement Methods

Other measurements like waist circumference can also show a more accurate interpretation of a person’s weight and their risk for conditions like heart disease and Type 2 diabetes. After all, weight itself isn’t a medical professional’s concern- it’s the conditions that can accompany an unhealthy weight. 

Lifestyle

Lastly, it’s important to examine someone’s overall diet and physical activity. Lifestyle is a crucial part of health status, and it’s one that every individual has control over when they have the right resources. 

The takeaway? “Health” is not a strictly-defined term. There are many attributes that play into being physically healthy, and BMI is just a single indicator. “Health” can also mean different things to different people. To one person, it might mean managing their diabetes, while to another it might mean being consistent with their hypertension medication. To someone, it might be living a life free of conditions despite a traditionally “overweight” BMI. One single measurement or condition does not define health.