BMI is not an accurate measure of health

A scale and a tape measure. BMI is calculated using one’s mass in kilograms and one’s height in meters. Photo by Pixabay/Pexels

During one of my high school gym classes, I remember my teacher putting up posters about the food pyramid and maintaining a healthy lifestyle and body mass index. BMI is commonly calculated as one’s mass in kilograms divided by the square of one’s height in meters or, in imperial measures, one’s mass in pounds divided by the square of one’s height in inches with that sum multiplied by 703. 

This ratio that uses mass and height was not just used in gym class to get us to exercise and eat healthier food — it is used in the medical field as well. The BMI calculation gives you a number that you match to a certain range on a chart. Depending on the range in which your number lies, you are deemed “underweight,” “healthy,” “overweight,” “obese” or “extremely obese.” You may have seen this colorful chart during an appointment with your primary care physician and your PCP may have even pointed out where exactly you fell on the chart. 

However, BMI is not an accurate measure of health and therefore should not be used as a metric at all. Just looking at the calculation to determine BMI, it is quite obvious that it does not take into account factors like muscle mass or bone density, both of which contribute to weight. 

BMI was first introduced in the early 19th century by Lambert Adolphe Jacques Quetelet, a Belgian mathematician with no connection to the field of medicine. Not only is the measure clearly outdated, but Quetelet has also been credited with the creation of anthropometry, which used physical aspects of criminals in order to categorize inmates. A subfield of anthropometry includes phrenology, an obsolete practice that involved taking measurements of people’s craniums and correlate it to intellect and mental capacities. Phrenology was often used to perpetuate racism and “prove” the inferiority of non-White races. 

Quetelet clearly had no expertise in medicine which he himself made clear. Quetelet stated that BMI was to be used as a statistical measure — not a measure of health — for populations, not individuals. In addition, fields such as anthropometry and phrenology, which Quetelet was influential in, are quite obviously outdated and rely on racist stereotypes. Yet, BMI is a measurement our society continues to use despite Quetelet’s lack of expertise in the fields of science and medicine and the fact that BMI was never supposed to be used in this way.

Predictably, especially based on Quetelet’s contributions to anthropometry and how it perpetuated racism, BMI is only somewhat reliable in measuring the height and weight of White, European men. BMI’s use in medicine today actively harms people of color, which is shown in studies that prove how Black and White populations have different body compositions and how White populations generally have lower BMI values than Black populations.

BMI works to harm people of color through different ways, such as by perpetuating stereotypes that cause people with higher BMI values to be treated differently and misdiagnosed. In an article from May 2021, The Washington Post told the story of Achea Redd, a 38-year-old Black woman, whose doctors did not listen to her when she voiced her concerns about possibly having an eating disorder because her BMI placed her in the “overweight” category. Redd was finally diagnosed with atypical anorexia, which does not present with a low body weight. 

When BMI is used as a valid medical measurement, it is used as an excuse for physicians and other medical professionals to ignore many of their patients’ concerns. A 2015 study exemplified this as well, showing how stigma regarding obesity can severely reduce the quality-of-care patients receive, leading to negative outcomes for patients. 

On the opposite side, in 2017 Newsweek told the story of Kanta Patel, a 73-year-old woman who had emigrated from India in the 1960s, had a BMI of 19 — putting her in the healthy category for her height — yet she was diagnosed with hypertension and was a borderline Type 2 diabetic. This instance, and other studies, have shown that Asian populations, especially South Asians, tend to have lower BMI values, yet other factors such as environment and family medical history put them at risk for cardiovascular disease, stroke and Type 2 diabetes which doctors will not always look for in patients with lower BMI values. Thus, these patients are put at an immense risk for being undiagnosed. 

In addition to perpetuating stereotypes, BMI also overtly discriminates against certain patient populations, which is seen through insurance charges. In certain cases, insurance will not cover procedures or treatments for certain patients depending on their BMI value. In Redd’s case, for example, insurance did not cover treatment for her anorexia simply because her BMI is considered “overweight.” Therefore, Redd began paying up to $800 a month from her own pocket in order to work with a dietician and a therapist. Insurance often also charges more for patients with higher BMI values as these higher values are correlated with poorer health outcomes, although several factors play into poor health outcomes. 

However, just about any basic statistics class will drill one thing into your head: correlation does not equal causation. In this case, a higher BMI does not automatically cause people to have worse health or more health conditions. 

Putting all the pieces together looks like this: White patients tend to have lower BMI values as the metric was made with White, European men in mind, which is reported to insurance, and therefore many of their procedures are covered and physicians do not overlook their conditions as frequently. However, Black patients, for example, often have a higher BMI because the metric was not made with them in mind. Since many have a higher BMI, doctors often overlook many of their health conditions. When they overlook these conditions, their health worsens — due to this and other products of medical and systemic racism — as they do not receive the treatment they need. Therefore, what looks like a simple correlation of “higher BMI equals poor health outcomes,” is actually a much more complicated issue. 

This issue is getting more and more attention — just a few weeks ago, I was watching “Grey’s Anatomy” (yes, the show is still on. And yes, it was just renewed for season 19) and Dr. Miranda Bailey, played by Chandra Wilson, talks about how BMI is an outdated, ineffective measure. 

“Well stop looking at the BMI. It’s stupid. The Body Mass Index is a fancy title and formula that was developed like 200 years ago by a mathematician. It doesn’t account for differences in the density of bones or muscle tones or fat. It looks at numbers, not distribution. So, stop looking at it and examine the patient” said Wilson as Dr. Bailey in the “Grey’s Anatomy” episode “Living in a House Divided.” 

BMI should not continue to be a valued measure of a person’s health; it contributes to medical racism, poor patient outcomes, high insurance charges and it prevents physicians from adequately treating their patients. Although this issue is garnering more attention, it is still used as a valid measurement and will continue to be used until adequate changes are implemented in the medical field. 

Physicians, and other medical professionals as well, need to be better taught about how BMI alone is not a good metric for determining individuals’ health. Instead, patients need to be viewed more holistically so they get proper health care and treatment. 

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