We are being held hostage by the BMI
There seems to be a hostage situation happening to our healthcare, and almost everyone has been coerced into complicity.
The captor isn’t a person, an organization, or a disease. It’s a 200-year-old mathematical calculation originally invented by a statistician who explicitly stated it had no place in evaluating individual health. Yet, step into a doctor’s office, apply for insurance, or enter an eating disorder treatment program, and you will find that this single, arbitrary number holds significant power over how your body is treated, evaluated, and valued.
For anyone navigating diet culture or working to heal from an eating disorder, the Body Mass Index isn't just an outdated metric, it can become a barrier for recovery itself.
The origin of the BMI
The story of BMI began all the way back in 1832. A Belgian statistician Adolphe Quetelet developed what became known as the Quetelet Index: weight divided by height squared. Quetelet was interested in describing characteristics of what he called the “average man” and set out to understand patterns across populations. He was not creating a diagnostic tool for individual patients or a measure of personal health.
Then nearly 140 years later, American physiologist Ancel Keys revisited the equation and in 1972, he coined the term Body Mass Index, or BMI, and helped establish its use as a convenient measure of relative weight in population research. Again, the emphasis is on research and pattern-seeking, not for use in determining health. However, this 2-century old equation that was only designed to make comparisons between population groups eventually became increasingly adapted for making judgments about individuals and their health.
How did the BMI enter healthcare?
While Adolphe Quetelet originally created the formula in 1832 for population statistics and Ancel Keys rebranded it as "Body Mass Index" in 1972 for research, BMI’s transition into clinical use was heavily influenced by two main industries: life insurance and pharmaceutical companies.
Life Insurance Companies (1940-1980s)
Before public health agencies adopted BMI, life insurance companies in the USA like MetLife used height-and-weight tables to evaluate policyholder risk. They used “Ideal Weight Table” based on mortality data among their policyholders. These tables were used to charge higher premiums or to deny coverage to individuals based on their weight. So when health organizations began to standardize metrics, they drew heavily on this insurance data, embedding a commercially motivated insurance metric into clinical medicine.
Pharmaceutical Industry, Medicalization & Coverage (1990s-2000s)
The most explicit corporate lobbying around BMI occurred in the late 1990s, coinciding with the development of “anti-obesity” medications. In 1995, an organization called the International “Obesity” Task force (IOTF) was created in the UK to push for the recognition of “obesity” as a global disease epidemic. The IOTF was set up as a charity but was mostly funded by major pharmaceutical companies manufacturing weight loss drugs at the time. Then in 1997, the organization provided funding directly to the World Health Organization (WHO) to host a consultation on “obesity”. Members of IOTF drafted the report that officially standardized global BMI categories. This led to the U.S. National Institutes of Health (NIH) to revise its guidelines to align with the WHO.
Here’s the kick, this change ended up reclassifying almost 29 million Americans from “normal weight” to “overweight” overnight without any changes in their physical health. This instantly expanded the addressable market for dietary programs and pharmaceutical interventions. Canada followed suit with the same classification in 2003.
Once the lower thresholds were locked in globally, lobbying shifted toward ensuring treatments tied to BMI were reimbursable. This opened the door for insurers to cover medical weight management, bariatric surgeries, and drugs using BMI cutoffs as the universal threshold.
The downside of using the BMI
Inadequacies of BMI as a Health Metric
BMI is a simple mathematical ratio meant to describe the body of an “average man”. Its weight categories cannot distinguish between someone’s body composition which is what can correlate more with health markers. This means the BMI offers no information regarding where someone’s weight comes from. Our weight is the sum of lean muscle mass (including organs), bone density, fluid, and adipose tissue (aka fat). The ratio of someone’s body compositions of these components mostly comes down genetics with minor influences from lifestyle and environment. Therefore, an athlete and a desk job worker can share the same BMI despite having different body compositions.
Another problem with still using the BMI is its racial and demographic bias. Quetelet founded the equation using data primarily from European white men, and even when the BMI was adapted into healthcare, the basis of the equation was never challenged or updated. We know that body composition, muscle density, and fat distribution vary significantly across sex, age, and race, making uniform thresholds scientifically inaccurate and discriminatory across diverse populations.
Last but not least, given that weight itself has been a poor indicator of someone’s health status, BMI’s focus on weight categorization contributes little to health insights. Large-scale epidemiological studies demonstrate that millions of individuals classified as "overweight" or "obese" under BMI metrics can have normal blood pressure, insulin sensitivity, and lipid panels, while many "normal weight" individuals can exhibit metabolic dysfunction. Health can exist with varying body weights and sizes, just as negative health conditions can exist in “normal” body weight and sizes.
How BMI Fuels Diet Culture
Diet culture relies on the assumption that thinness equals appeal, health, and discipline, while larger bodies are assumed to reflect the opposite. The BMI can become the driver of these harmful beliefs. The sharp divisions of "underweight," "normal," "overweight," and "obese" classifications suggests that moving across categories instantly alters a person's health status. It places morality on body sizes where a higher BMI automatically signals a “correction”. This shifts the focus away from investigations into actual health behaviors like sleep, stress, movement, nourishment, and social determinants of health towards pushing weight suppress as the ultimate goal. And when lowering the BMI is prioritized above all else, dangerous weight-loss strategies that often involve significant caloric restriction, over-exercise, fasting, or using unverified supplements can become normalized and validated as long as they result in weight reduction.
Increasing the Risk of Eating Disorders
Overreliance on BMI in medical, educational, and social settings can accidentally acts as a significant trigger for the onset and escalation of eating disorders. When children and adolescents are being told of their BMI and the associated assumptions from these weight categories, it can inadvertently frame their developing bodies as problematic. More and more youth today have reported body dissatisfaction and many are dieting when they’re in need of additional nutrition for development and growth. Poor nutrition and body image are strong predictors of the development of eating disorders.
BMI’s role in fueling weight stigma also means people who have lost weight by practicing disordered eating or eating disorder behaviors are met with praise from healthcare providers, community members, and the culture at large. It further reinforces these dangerous behaviors under the guise of staying within a specific BMI category. At the end of the day, when individuals are taught that their health is dictated by a specific number range, we create shame when people are outside the “norm” box. This internalized weight bias directly correlates with increased rates of anxiety, depression, disordered eating patterns, and eating disorders.
How BMI Acts as a Barrier to Recovery
For people in treatment for eating disorders, the BMI can feel like a double-edged sword. Because weight restoration can be a critical component of medical recovery, in that context, BMI can provide clinicians with a standardized way to describe weight status and track change over time. Seeing BMI increase during nutritional rehabilitation can provide one objective indicator that weight restoration is occurring.
The problem is that BMI can very easily become more than a monitoring tool. For someone with an eating disorder, the number on the scale can become highly emotionally charged. A BMI can become a target to reach, a number to avoid exceeding, or a new rule around which the eating disorder organizes itself. This is particularly problematic because a BMI within a “normal” range does not necessarily mean that someone has recovered from an eating disorder. Psychological symptoms, restrictive behaviours, fear of weight gain, compulsive exercise, nutritional adequacy, and the person's ability to eat flexibly and participate in life all matter.
The use of BMI can also fuel the “not sick enough” myth that people with eating disorder commonly experience. People who are trapped in severe restrictive eating patterns, compulsive exercise regimes, or dangerous purging behaviors are frequently turned away from treatment or told they are "fine" simply because their BMI lands in the "normal" range or above “normal” ranges. The clinical practice guideline specifically addressing eating disorders in people with higher weight notes that these disorders have historically been under-recognized and under-treated, and emphasizes the importance of considering weight stigma in clinical care. A low BMI can appropriately prompt concern about nutritional status, but a higher BMI shouldn't mean that an eating disorder isn't just as serious.
Why is BMI still so widely used?
Given its known flaws, why hasn't healthcare abandoned BMI? Because it is simple, standardized, inexpensive and useful for certain population-level and clinical purposes.
To use the BMI, you only need height and weight, no specialized equipment, bloodwork, imaging or extensive assessment. At the end of the day, it’s fast and it’s cheap. This makes the BMI an appealing tool when healthcare systems need to assess large populations consistently. The CDC still describes it as a quick, low-cost screening measure and a valuable population-health measure. And once a measurement becomes embedded in clinical guidelines, research studies, health records, insurance polies etc, replacing it becomes much more complicated. The healthcare systems have essentially been built around it, making it very difficult to replace.
And that’s our biggest problem, there isn’t one universally accepted replacement.
Current Reassessment
Because BMI was adopted largely due to population-level convenience and corporate backing rather than its accuracy as an individual diagnostic tool, medical bodies have begun backing away from it. In 2023, the American Medical Association (AMA) issued policy guidance urging physicians to move away from using BMI as a standalone metric, citing its historical flaws, racial bias in baseline data, and inability to differentiate between body composition.
Canada is in a similar place, our systems haven’t exactly broken up with BMI. We're more in the awkward phase of realizing that the relationship isn't working quite the way we thought it was. BMI remains embedded in Canadian public-health surveillance because it is inexpensive, standardized and useful for looking at patterns across large populations. But even Health Canada's own guidelines acknowledge that BMI is a population-derived measure and that, when applied to an individual, it is only one part of a much broader assessment.
The Path Forward
Medical consensus is gradually shifting. Rather than treating BMI as a definitive diagnosis, experts increasingly advocate using it solely as a preliminary screening marker alongside metabolic blood panels, waist measurements, and overall physiological function to form a complete picture of health.
Perhaps this is where the future of BMI lies: not necessarily in eliminating the number, but in putting it back in its place. A BMI can describe a relationship between height and weight. It cannot tell us how someone eats, how rapidly their weight has changed, whether they are medically stable, whether they are restricting, or whether they are psychologically well. It certainly cannot tell us what kind of person someone is.
In eating-disorder care, we can monitor weight when weight is clinically relevant without making a number synonymous with health. And we can talk about bodies without turning people into their measurements. Maybe moving beyond BMI doesn't mean moving beyond numbers altogether. Maybe it means moving beyond the idea that one number can tell the whole story.
Disclaimer: the information provided is not intended as medical advice or to diagnose or treat a medical disease. It is strictly for informational purposes. Consult with your medical provider such as a dietitian before implementing any dietary changes, the information provided does not replace medical advice provided by your healthcare provider.
Created with AI assistance by Abby Hsiao, Dietitian
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Work Cited
American Diabetes Association Professional Practice Committee. (2026). Screening, diagnosis, evaluation, and staging of obesity in adults: Standards of Care in Overweight and Obesity—2026. Diabetes Care. https://doi.org/10.2337/doci26-0003
American Medical Association. (n.d.). Rethinking overreliance on BMI to improve patient care. American Medical Association
American Medical Association. (n.d.). Support for evidence-based use of BMI as a measure in medicine H-440.797. American Medical Association policy
American Medical Association. (2023). Use of BMI alone is an imperfect clinical measure. American Medical Association
Bidstrup, H., et al. (2022). Internalised weight stigma as a mediator of the relationship between experienced/perceived weight stigma and biopsychosocial outcomes: A systematic review. International Journal of Obesity, 46, 1–14. https://doi.org/10.1038/s41366-021-00982-4
Centers for Disease Control and Prevention. (n.d.). About body mass index (BMI). Centers for Disease Control and Prevention
Eknoyan, G. (2008). Adolphe Quetelet (1796–1874)—the average man and indices of obesity. Nephrology Dialysis Transplantation, 23(1), 47–51. https://doi.org/10.1093/ndt/gfm517
Emmer, C., Bosnjak, M., & Mata, J. (2020). The association between weight stigma and mental health: A meta-analysis. Obesity Reviews, 21(1), e12935. https://doi.org/10.1111/obr.12935
House, E. T., Gow, M. L., Lister, N. B., Baur, L. A., Garnett, S. P., Paxton, S. J., & Jebeile, H. (2021). Pediatric weight management, dietary restraint, dieting, and eating disorder risk: A systematic review. Nutrition Reviews, 79(10), 1114–1133. https://doi.org/10.1093/nutrit/nuaa127
Moynihan, R. (2006). Obesity task force linked to WHO takes “millions” from drug firms. BMJ, 332(7555), 1412. https://doi.org/10.1136/bmj.332.7555.1412-a
National Institute for Health and Care Excellence. (2017). Eating disorders: Recognition and treatment (NG69). NICE
Pearl, R. L., & Puhl, R. M. (2018). Weight bias internalization and health: A systematic review. Obesity Reviews, 19(8), 1141–1163. https://doi.org/10.1111/obr.12701
Rasmussen, N. (2019). Downsizing obesity: On Ancel Keys, the origins of BMI, and the neglect of excess weight as a health hazard in the United States from the 1950s to 1970s. Journal of the History of the Behavioral Sciences.
Stang, A. J. (2022). Is it time to say goodbye to BMI? Plastic and Reconstructive Surgery—Global Open, 10(1), e4039. https://doi.org/10.1097/GOX.0000000000004039
Young, J. (2023). AMA Code of Medical Ethics’ opinions related to clinical use of BMI. AMA Journal of Ethics, 25(7), E514–E516. https://doi.org/10.1001/amajethics.2023.514
