Myth: BMI indicates a “healthy” or “unhealthy” body
The history of BMI dates back to 1832. Adolphe Quetelet (1796-1874), a Belgian statistician, mathematician, and astronomer, was inspired by his passion for statistical analysis and bell-shaped curves to establish quantifiable characteristics of the "normal man” (Pray & Riskin, 2023). It’s crazy that someone who wasn’t even working in healthcare created something that gets treated as though it’s a reliable shortcut to knowing someone’s health status. Many assume that if your BMI is in the “normal” range you're healthy, if it’s “overweight” or “obese,” you’re not. But health is far more complex than one this simple calculation can capture, and using BMI alone is extremely misleading for both individuals and clinicians.
Myth vs. Reality
So you’re probably wondering why we even use BMI anymore? It has to be giving us some sort of insight, right? While BMI may show some associations, there we need to consider this viewpoint: People who sleep fewer than 6 hours per night are at increased statistical risk for certain diseases — but we don’t assume that everyone sleeping 5.5 hours is doomed, disordered, or needs medical intervention. It’s one single data point, not a diagnosis. The same viewpoint should be applied to BMI. Yes, BMI does correlate with some health risks at a population level—it’s cheap, easy, and for many people higher BMI is associated with increased risk of type 2 diabetes, cardiovascular disease, etc. However, it has serious limitations when applied to individuals. BMI doesn’t distinguish between fat vs. muscle mass, fat location (visceral vs. peripheral), bone density, or differences by sex, age, race/ethnicity—all of which can meaningfully change health risk (Sweatt et al., 2024). BMI’s cutoff points are arbitrary in some populations, misclassify risk, and quite frankly for some people with an “overweight” BMI there’s no elevated disease risk (Byker Shanks et al., 2025). Also, studies of athletes show that high BMI often classifies very muscular, fit people as “obese” even when they have low body fat (Byker Shanks et al., 2025). So while BMI can flag risk, assuming it always gives an accurate picture for any given person can lead to both false alarms and missed issues. Risk ≠ destiny. Risk ≠ causation. And risk cuts both ways. BMI is just being given moral weight because diet culture made it so.
What Actually Matters
While there are physical metrics that matter more than your BMI (how your body is composed, bloodwork markers, overall lifestyle, etc.) something that matters far more is how a focus on BMI can impact how providers treat patients. The current focus on BMI has created a social stigma where those who fall on the higher end of the BMI avoid getting medical help even when they really need it (Mensinger et al., 2018). Too many doctors have told them that the solution to their health problem is to “just lose weight” and don’t even take their symptoms into consideration. Someone can have great health markers, participate in movement, and still have an elevated BMI - there are examples of people like this who can run ultramarathons without blinking an eye! While someone with a “normal” BMI and a poor diet, low activity, or poor metabolic markers may actually be at higher risk for poor health than their BMI suggests. BMI is best used as a first screen—not the full story.
So, BMI can be useful, especially for population-level monitoring —but believing it’s an accurate predictor of health for everyone is a myth that can lead to misjudgments and unnecessary worry. Reach out to us if you want to dive deeper into this topic on an individual level!
References
Byker Shanks, C., et al. (2025). BMI or not to BMI? Debating the value of body mass index as a clinical metric across populations. International Journal of Behavioral Nutrition and Physical Activity. https://doi.org/10.1186/s12966-025-01719-6
Mensinger, J. L., Tylka, T. L., & Calamari, M. E. (2018). Mechanisms underlying weight status and healthcare avoidance in women: A study of weight stigma, body-related shame and guilt, and healthcare stress. Body image, 25, 139-147.
Pray, R., & Riskin, S. (2023). The History and Faults of the Body Mass Index and Where to Look Next: A Literature Review. Cureus, 15(11), e48230. https://doi.org/10.7759/cureus.48230
Sweatt, K., et al. (2024). Strengths and limitations of BMI in the diagnosis of obesity: A review of current literature. Journal of Obesity Research & Clinical Practice, 13(2), 101-115. https://doi.org/10.1016/j.jorcpi.2024.01.005