The Origins Of BMI Are Further Removed From Medical Science Than You Knew

When your doctor's office checks your height and weight, you're probably given an estimate of your body mass index (BMI) to see if you fall within a "healthy" weight range. After all, someone who weighs 150 pounds at 6 feet tall will look very different from someone who weighs the same at 5 feet tall. By BMI standards, you're classified as overweight if your score is 25 or above — a category that includes about 1 in 3 people in the United States, according to the National Institutes of Diabetes and Digestive and Kidney Diseases.

But if you have a lot of muscle, BMI can be misleading. You could be labeled "overweight" even with visible abs. Strength coach Gordana Velinović shared on Instagram that she's considered overweight by BMI, despite having just 15% body fat. The formula also doesn't account for health factors like high cholesterol or elevated blood sugar, which can occur at any weight. In other words, a "healthy" BMI doesn't necessarily mean you're actually healthy.

In fact, BMI wasn't originally designed to measure individual health at all. The formula came from a Belgian astronomer — yes, someone who studies planets and stars — named Adolphe Quetelet. According to the University of Rochester Medical Center, he created it in the 19th century as part of a census in the Netherlands, aiming to determine the "ideal body weight" based on data from wealthy white men.

Insurance companies started using BMI in the 1950s as a quick way to estimate health risks. According to a 2023 review in Cureus, researchers liked the BMI measure because it was simple and fast to calculate. However, most of the early studies were based on white men. That means BMI doesn't account for important differences among racial and ethnic groups. For example, people of Asian ethnicity may have a lower BMI but carry more body fat, putting them at higher risk for diabetes and heart disease, even when their BMI is in the "normal" range.

BMI also can't tell the difference between fat and muscle, and it doesn't reveal where that fat is stored. This matters because visceral fat (aka "belly fat") is more strongly linked to health risks than subcutaneous fat (fat under the skin). BMI also ignores sex differences. Men typically store more fat around the abdomen, while women often store more in the hips and thighs. That hip and thigh fat may actually offer some protection against heart disease and type 2 diabetes.

Today, many researchers urge health professionals to look beyond BMI and use other measurements like waist-to-hip ratio, waist-to-height ratio, or waist circumference to better predict health and mortality risks. In fact, waist-to-height ratio tends to be a stronger predictor of heart disease than BMI, and waist circumference has a closer link to the risk of certain diseases.

BMI is still widely used as the benchmark for determining whether someone qualifies for weight loss medications or bariatric surgery. For example, people with a BMI of 30 or a BMI of 27 paired with type 2 diabetes or high blood pressure may be eligible for GLP-1 drugs like Ozempic. Bariatric surgery is typically considered only for those with a BMI of 35 or higher, or a BMI over 30 accompanied by an obesity-related health condition. The Centers for Disease Control and Prevention says that BMI remains a key factor in shaping population-level health decisions.

On an individual level, however, BMI alone may not provide a full picture of your health risks. In 2023, the American Medical Association (AMA) formally acknowledged the limitations of BMI in diagnosing obesity and predicting health outcomes. Rather than relying on BMI as the sole measure, the AMA recommends using it alongside other assessments, such as visceral fat levels, body composition, and metabolic markers such as blood sugar and cholesterol levels. Your doctor may also take into account your medical and family history, diet, exercise habits, and sleep patterns when evaluating your risk for chronic disease.