Body mass index has functioned as medicine’s default screening tool for individuals since the World Health Organization formally classified obesity as a global epidemic in 1997 — despite having been designed more than a century earlier as a statistical tool for populations, not patients.
According to the report, BMI was originally developed by mathematician Adolphe Quetelet in the early 19th century to document height and weight averages across large groups. Its adoption into clinical practice came through a 1970s study suggesting it could track obesity trends at the population level. As obesity rates continued rising, convenience drove its expansion into individual healthcare assessments — a transition that critics say was never scientifically justified.
Francesco Rubino at King’s College London is direct on the point: “There is no logic, no medical coherence to using BMI to define a disease. It’s just not suitable.” The formula itself — weight in kilograms divided by height in meters squared — produces a single number that places individuals below 18.5 as underweight, above 25 as overweight, and above 30 as obese. It does not account for where fat is stored, what tissue type is producing the number, or how those factors interact with actual disease risk.
What the number misses
The structural limitations are well-documented. BMI cannot distinguish between muscle mass and fat mass, which is why many athletes register as overweight or obese despite low body fat and high cardiovascular fitness. It also treats the body as uniform, ignoring the clinical distinction between visceral fat — stored in and around organs, predominantly in men, and strongly associated with metabolic disease — and subcutaneous fat on the arms, thighs, and lower body, which carries a comparatively lower health risk.
The consequences of relying on this number extend beyond misclassification. According to the report, BMI cut-offs currently govern access to knee surgeries, GLP-1 medications, infertility treatment, gender-affirming care, and bariatric procedures. Patients outside the “acceptable” range may be denied care regardless of other clinical indicators, while individuals with “normal” BMI scores but elevated metabolic risk may go unidentified entirely.
The inverse failure is equally documented. A person can fall within a clinically “normal” BMI range while lacking sufficient body fat to sustain regular menstruation — a deficit associated with bone weakness, cardiovascular complications, and pelvic pain.
A consensus taking shape
After three decades as standard practice, the report indicates a consensus is now forming within medicine that BMI is not a suitable individual diagnostic measure. The search for replacement metrics is underway, with researchers and clinicians pushing toward tools that account for fat distribution, tissue composition, and metabolic markers — factors that BMI systematically ignores.
The broader implication, as the report frames it, is not simply a matter of swapping one measurement for another. The inadequacy of BMI is forcing a more fundamental reassessment of how medicine defines the relationship between body size and health — and what clinical evidence should actually determine access to care.
Photo by Pixabay
This article is a curated summary based on third-party sources. Source: Read the original article
