Why BMI is a BS Health Marker

Last week we went back in time to the 1860’s when the Pony Express was thriving and the calorie was invented. This week we’re going back even further to learn about the ever-so-flawed BMI (Body Mass Index).

The BMI was invented in the 1830s by Adolphe Quetelet, a Belgian mathematician and sociologist. It was created as a way to generalize obesity trends in large populations by essentially dividing an individual’s weight by height.

Let me back track for a second and remind you that in the 1830s settlers were traveling west in wagons for the first time via the Oregon Trail, and Charles Darwin had just set sail aboard the H.M.S. Beagle. So when the BMI was invented, a calculation that is still being used by physicians and insurance companies today, evolution wasn’t even a thing yet. Just keep that in mind as you read on.

The BMI was later introduced into the scientific community by Ancel Keys in the Journal of Chronic Diseases in 1972. Keys noted that the BMI was not satisfactory for measuring an individual’s health, but was as good as any other relative weight index for studying general population trends.

However, this little tidbit was lost upon the American public and the BMI quickly became an easy and convenient tool for doctors and health insurance companies to determine the health of their patients/customers and their risk factor for diseases.

So what’s the problem?

The problem is that the BMI is an oversimplified calculation that only measures the ratio of height to weight without taking into account body composition, bone structure, hydration levels, and ethnicity. A physically fit and athletic individual (person A) with proportionately low body fat and high lean muscle mass will have a higher BMI than someone (person B) of the same height who has more body fat and less muscle mass.

Person A would then automatically be considered ‘at risk’ for Type 2 Diabetes, hypertension, arthritis, certain forms of cancer, high cholesterol and liver disease when they are actually “healthier” than person B based on their active lifestyle and behaviors.

Take my pal Noah for example. Noah is quite literally one of the strongest folks I know, and as a fitness professional, he prides himself on being a pretty healthy guy. However, Noah stands at 5’ 10” and weighs in at 215 lbs, giving him a BMI of 30.8. Noah is technically classified as obese. Noah can back squat 540 lbs and has a body fat percentage that hovers around 12%. He’s fit, strong, and as far as I know does not suffer from any chronic illness correlated with obesity. However, with this label of obesity, he may be subject to higher health insurance premiums than his lower BMI counterparts. His doctor could also technically prescribe him weight loss pills without any symptoms of disease present. 

This is Noah. Noah is technically obese.

This is Noah. Noah is technically obese.

Noah is pretty much solid muscle and can back squat 540 lbs. He wanted me to emphasize that this 540 lb PR was a full depth squat, as shown. I want to emphasize the fact that he’s repeating the exact same outfit on two different days.

Noah is pretty much solid muscle and can back squat 540 lbs. He wanted me to emphasize that this 540 lb PR was a full depth squat, as shown. I want to emphasize the fact that he’s repeating the exact same outfit on two different days.

Personal anecdotes aside, it is a known fact that the BMI overestimates up to 10% for tall individuals and underestimates by the same amount for shorter people. This means that people are arbitrarily being classified as ‘normal’ or ‘overweight’ based on science from 200 years ago.

A study conducted to determine the accuracy of BMI in determining cardiovascular health found that nearly half of individuals with a BMI that classified them as overweight had a healthy cardiometabolic profile. On the other hand, about one third of ‘normal’ individuals had cardiomatebolic health risks present.

This inaccurately labels millions of people as unhealthy while giving a false sense of security to others who are deemed ‘normal’.

Speaking of arbitrary classifications, in 1998 the normal/overweight BMI cut-off was lowered from 27.1 to 25 by the National Institute of Health and the Center for Disease Control and Prevention. This policy change put 29 million previously healthy individuals into the overweight category and pushed millions more into the obese category, giving insurance and pharmaceutical companies an opportunity to cash in on higher premiums and weight loss pills/surgeries respectively.

So…if not the BMI, how should we measure health? 

The BMI was not created to be a diagnostic tool or a marker for individual health, and it shouldn’t be used as one. Factors such as resting blood pressure, cholesterol, blood sugar levels, resting heart rate, health behaviors, and mental health should all be looked at. You cannot determine a person’s health simply by weighing them, looking at them or just taking only one of the previously mentioned measures into account. The whole person has to be considered.

Using BMI as an indicator of health is inaccurate, stigmatizing, and about as relevant as categorizing people’s health based on their shoe size. If you find your doctor using your BMI against you at your next doctor’s appointment, make sure to advocate for yourself and encourage him or her to look at z collection of other markers to determine your health and risk of disease.

If you’re confused about weight, dieting, what to eat and how to take care of your body, ask me about The Body Love Blueprint, my 12-week online group coaching course designed to help you make peace with your plate and improve your body confidence without #fakenews like calorie counting or BMI.

With love,

Kate

Resources for further learning:

Take Two - BMI tells an incomplete story of obesity

NPR - Top 10 Reasons Why BMI is Bogus

VOX - Why BMI is a Flawed Measure of Body Fat Explained by an Eloquent 14-Year-Old

Medical News Today - Why BMI is Inaccurate and Misleading

Kate Telge