The problematic origins of BMI
The history of BMI and its perpetuation of weight stigma and medical discrimination.
The Body Mass Index has become a standardized measurement of body mass used by doctors, insurance companies, and fitness and wellness experts as an indicator of health.
But BMI’s contributions to medical discourse laid the groundwork for widespread weight stigma, and has been used to justify medical discrimination, fatphobia and medical racism.
The BMI was invented by Adolphe Jacques Quetelet, a mathematician who also studied astronomy, statistics and sociology. Quetelet had no intentions for BMI to become a standardized tool to measure individual health—his work with BMI was part of a sociological quest to determine an average mathematical weight for l’homme moyen— the average man.
Quetelet’s model was derived solely from French and Scottish participants and excluded any other participants who weren’t white Europeans. In its origin, Quetelet’s model suggests that there was an average standard of body mass, so long as they resembled the average white European man. Eventually, Quetelet’s work would be used as scientific justification for eugenics—the sterilization of people of colour, immigrants, and disabled people.
The BMI, calculated by a person’s weight in kilograms divided by their height in meters squared, is a mathematical formula that was never intended to determine individual body mass or health. But by the 20th century, American insurance companies began adopting Quetelet’s model as a way to determine coverage for policyholders. As a result, the concept of weight as an indicator of health began to take root, and its trend is outlived to this day.
According to the BMI, a person is considered obese if the mathematical calculation of their height divided by their weight resulted in a score of 30 or above. Based on this rubric, former NFL running back Marshawn Lynch would be considered obese, and Muhammad Ali would be considered overweight. This is because the BMI does not distinguish muscle from fat and doesn’t factor in bone structure, age, sex, or ethnicity.
Quetelet was not a doctor or medical professional—his mathematical study of the human body was centered around white European standards. Naturally, the BMI is often then inaccurate in determining individual health in people of color. It has consistently overestimated obesity and health risks in Black people, and underestimates health risks for Asians. According to The Journal of the American Medical Association, higher BMIs among certain groups of people can be more optimal, while some groups with lower BMIs tend to be at higher risk of metabolic disorders.
The use of BMI is widespread and recognized by the World Health Organization. Visitors of the WHO’s BMI webpage are greeted with a mention of obesity and its death toll, directly linking individual health with the BMI. However, the BMI only accurately predicts obesity in patients of color less than 50% of the time. Despite not always accurately determining individual health in patients, above average weight is still considered “unhealthy” and categorically labeled as “at risk.” As a result, medical discrimination due to weight stigma have become increasingly frequent.
Conversations of BMI and weight stigma have recently surfaced on social media platforms, with Canadian public health officials’ recommending that those considered obese would be “at risk” and prioritized for the Covid-19 vaccine. Medical discrimination due to weight bias is common and well documented. Patients with larger bodies are often chastised, misdiagnosed, and receive less quality care.
As officials ramp up vaccination efforts to combat the Covid-19 pandemic, weight stigma poses a public health concern. Patients with larger bodies often experience judgmental and negative attitudes from healthcare professionals, which generally reduces their desire to seek health care. According to CTV News, justifications to friends and family that a patient’s body size is reasoning for their vaccine priority discourages bigger people from getting vaccinated.
While the BMI draws a direct correlation between larger bodies with severe health risks such as heart disease and stroke, it is well documented that medical bias of patients with larger bodies receive less quality care from health professionals. The risk of unvaccinated populations discouraged from weight bias poses a threat to Canadian public health, in conjuction with medical discrimination.
