When a 200-year-old metric meets modern medicine

In the 1830s, a European scientist named Adolphe Quetelet set out to define the "ideal form" of the average white male. He was not trying to invent a medical screening tool. Yet nearly two centuries later, the formula he devised—body mass index, or BMI—remains the standard way doctors assess whether a patient's weight puts them at risk for conditions like heart disease and type 2 diabetes. As Atlantic staff writer Katie Wu puts it, "It was never intended for medical use." And that origin story has become increasingly hard to ignore as researchers and clinicians confront the metric's shortcomings, especially when applied across the globe's billions of people with different sexes, genders, heritages, muscle mass, and lifestyles.

The problem with a one-size-fits-all number

BMI is simple: it factors only height and weight, two numbers already in every patient's chart. That convenience is why it has persisted. But the simplicity is also its weakness. "There are people with, you know, quote unquote high or overweight obese BMIs who are extremely healthy," Wu notes. "Many athletes are a classic example. And conversely, plenty of people in the technically healthy weight category who are experiencing all sorts of metabolic issues."