Is BMI outdated? Here's what the science actually says
- Harry Checkley
- Mar 12
- 5 min read
The 190-Year-Old Formula Still Running Your Health Assessment
Is BMI outdated? It's a question more doctors, researchers and patients are asking and the evidence suggests the answer is yes. BMI has been the standard measure of healthy weight for decades, yet it was never designed to assess individual health in the first place, just populations.
You've probably had your BMI calculated at some point. A quick calculation based on your height and weight, puts you into one of these categories:
Underweight
Healthy
Overweight
Obese
That number is then used to make judgement about your health. But what if it was never designed to tell you anything meaningful about your body specifically?
Where BMI Came From
BMI was created in the 1830s by a Belgian mathematician named Adolphe Quetelet. He wasn't a doctor. He wasn't studying patients. He was analysing population statistics, trying to describe the average proportions of the human body across large groups of people.
He called it the Quetelet Index. It was never intended to assess whether any individual person was healthy.
It wasn't until the mid-20th century that the insurance industry adopted it as a quick screening tool, and from there it gradually embedded itself into clinical practice worldwide. It has barely changed since.
Is BMI Accurate? What It Measures and What It Misses
BMI is a simple calculation: your weight in kilograms divided by your height in meters squared. That's it.
It has no way of distinguishing between fat and muscle. It has no idea where fat is stored in your body. It treats a highly trained athlete and a sedentary person of identical height and weight as medically equivalent.
Consider two women. Same height. Same weight. Same BMI score. One is a recreational runner with low body fat. One carries most of her weight as visceral fat around her waist and organs. BMI gives them the same number.
That's not a useful health metric. That's a coin flip.
Why Fat Distribution Matters More Than Your BMI Score
Not all fat is equal. This is where BMI inaccuracy becomes genuinely dangerous.
Visceral fat, stored deep in the abdomen surrounding your organs, is strongly associated with elevated risk of cardiovascular disease, type 2 diabetes, and metabolic syndrome. Subcutaneous fat, stored just beneath the skin around the hips and thighs, carries significantly lower risk.
BMI sees total weight. It doesn't see distribution, but weight distribution is everything.
Two people can have identical BMI scores and radically different metabolic risk profiles depending purely on where their body stores fat. A metric that cannot capture this distinction is missing the information that actually matters clinically.
Why Doctors Are Calling BMI Outdated
In 2023, the American Medical Association officially updated its guidance, recognising that BMI alone is an imperfect and sometimes misleading measure of individual health. This followed decades of researchers raising the same concerns.
A landmark study published in the International Journal of Obesity involving 13,601 subjects found that BMI misclassified more than half of people with excess body fat. Among men, BMI identified 19% as having excess body fat, direct measurement found 44%. Among women, 25% versus 52%.
The tool most of us rely on to understand our weight-related health risk is missing the majority of people it should be identifying.
Beyond BMI: What Should We Be Using Instead?
Body composition measurement goes beyond a single number. It looks at:
How much of your body weight is fat versus muscle versus water
Where that fat is distributed in the body
Your waist-to-height ratio as a stronger predictor of cardio-metabolic risk than BMI
How all of these things change over time
When you track body composition rather than just weight, you start to understand your body rather than simply measure it. That's a fundamentally different and more useful relationship with your own health data.
Until recently, this level of insight required clinical equipment such as DEXA scanners, specialist appointments and significant cost. It existed in hospitals and research centers, not in people's daily lives.
Beyond BMI: Body Composition Tracking for Everyday Life
The Body Volume Index was developed as a scientifically grounded alternative to BMI, with a research relationship with Mayo Clinic spanning nearly 20 years.
In 2017, Mayo Clinic validated the same BVI technology as used in myBVI against the Bod-Pod, a clinical gold standard for body composition measurement. Across 1,215 subjects at Mayo Clinic's employee wellness centre, the correlation between BVI and clinical measurement was R² = 0.9845, demonstrating that BVI body composition measurement is comparable to methods used in specialist clinical settings.
Then in 2024, a study published in the European Heart Journal: Digital Health took that validation further, testing the myBVI mobile app specifically across 1,280 subjects at Mayo Clinic's executive wellness programme. The results were striking: myBVI achieved an AUC (Area Under the Curve) of 0.88 for identifying cardio-metabolic risk, outperforming BMI (0.77), waist-to-hip ratio (0.77) and waist circumference (0.79).
In plain terms, AUC measures how accurately a tool identifies health risk. A score of 1.0 is perfect. A score of 0.5 is no better than chance.
myBVI at 0.88 significantly outperformed every traditional measure tested.
Using just two photos taken on your smartphone, myBVI analyses your body shape and fat distribution and tracks how it changes over time.
No clinic appointment. No expensive equipment. No complicated process.
Just clearer, more meaningful insight into what your body is actually doing.
Conclusion: Is BMI Outdated?
The evidence says yes! BMI had its moment and the inventor of it in 1835 never meant it to be used the way it is used today to make decisions about individual patients . As a population-level screening tool it does serve some purpose. The simple truth is that a formula invented 190 years ago by a mathematician studying averages was never designed to tell your own individual health story.
Your body is more complex than a single number. The science has known this for decades. The tools to do better now exist and they fit in your pocket.
Ready to See Beyond the Number?
Download myBVI free and start tracking what actually matters.
References
Romero-Corral et al. (2008). Accuracy of body mass index in diagnosing obesity in the adult general population. International Journal of Obesity. 766 Scopus citations. [https://pubmed.ncbi.nlm.nih.gov/18283284/]
European Heart Journal — Digital Health (September 2024). Validation of myBVI mobile application for cardio-metabolic risk assessment at Mayo Clinic. [https://academic.oup.com/ehjdh/article/5/5/582/7733847]
American Medical Association (2023). AMA adopts new policy clarifying role of BMI as a measure in medicine. [https://www.ama-assn.org/press-center/ama-press-releases/ama-adopts-new-policy-clarifying-role-bmi-measure-medicine]
Comments