BMI: Should we be using it to determine one's health?
By Katherine Metzelaar, MSN, RDN, CD
BMI: Body Mass Index.
It’s been used in every gym class, doctors room, news report, and research study. You have been told that it is a “marker of health.” You may have felt shame, blame and guilt for what category you fall under on the BMI scale, or possibly you have experienced fear of switching into a higher BMI category. You have used the BMI language of “normal, overweight, and obese” to describe other people’s bodies and maybe even your own. But, have you ever stopped to question the origins of BMI? Most likely not because after all, why would you considering its ubiquity?
Let’s take a look.
The history: BMI was invented in the mid-1800s by a mathematician, statistician and astronomer named Adolphe Quetelet, who had a thing for understanding the characteristics of what made up the “average man.” And who exactly did that include at the time? White, able-bodied males. So, he quested and quested, as statisticians do considering their affinity for plotting numbers on graphs, in order to create comparative standards to understand the defining characteristics of men and how they differed from one another. Meaning, if he could understand the “average” man then he could compare and contrast others to that standard. Thus, he created the equation “Quetelet’s Index.”
Interesting additional fact: It wasn’t until 1972 that Ancel Keys renamed this equation the “Body Mass Index” and decided it was a “superior way of measuring fat” in a person, even though the original equation was never created for such purpose. It was around this time that the Metropolitan Insurance Company was searching for a way to charge their clients in larger bodies a higher premium and thus started using BMI for that purpose.
First issue: Seriously?!
Problems so far: Developed in the 19th century by a statistician (?!?!?), not a physician or medical professional; it was not intended for individual use; it was created from the study of white, able-bodied males intended for population analysis; it was re-branded and sold to the population at large many years after its original creation; and later it was used as a way to charge people higher premiums. The BMI at its core does not take into account ethnicity, ability, race, or sex.
Second issue: Don’t make the medical professionals work too hard
It’s incredibly simplistic. The health of individuals is SO complex and to say that an equation, that takes your weight (lbs) divided by your height (inches) squared times 703, is enough to determine one’s health status is…well, absurd. It doesn’t take into account bone density or muscle mass, all of which can vary from person to person. The BMI also doesn’t have a way to include the social determinants of health, which impact the health of an individual significantly.
Third issue: Let’s pretend that nothing else matters but your weight
It ignores behaviors. Study after study has shown us that health behaviors, regardless of weight loss, improves the overall health of the individual. Even the CDC has openly stated that the “BMI is not a diagnostic of the health of an individual,” and yet many institutions are still using this outdated, problematic, simplistic equation to determine “health.” Using the BMI may make it easier for a medical professional to have a quick, short appointment, instead of doing a throughout assessment, that includes asking questions and listening to their patient/client. But, there is so much harm done, so many assumptions made, and so much weight stigma in action when using the BMI in such a way.
Fourth issue: We just feel like changing the BMI ranges
Numbers assigned to BMI categories have changed. Why does this matter? The NIH (National Institutes of Health) has continued to change and lower the number ranges that constitute each BMI category over the years, which have been arbitrarily assigned. Meaning, there were large conferences held at different points in time where those in power at the NIH and CDC decided that the numbers that constitute each BMI category would be lowered because the numbers were more “even” and “easier to remember,” despite advice against doing so from many health professionals around the country. The numbers have been lowered based on feelings and not research which is incredibility problematic.
It’s abundantly clear that we should not use BMI as a tool or measurement to determine one’s health. Its origins are unscientific; exclude ethnicity, sex, and race; doesn’t include the variability of muscle tissue and bone density, and ignores the impact of health behaviors by focusing exclusively on a person’s weight. The BMI enforces weight stigma and prevents people from getting the support they need.
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