• A new report recommends doctors stop using Body Mass Index to diagnose obesity because it isn't nuanced enough.
• Doctors should consider a patient's overall health instead of their weight, it said.
• A leading obesity expert told Business Insider why BMI is bogus and how to better assess the risk of overweight.

The previous version of this story was published in 2022, when Business Insider spoke to Dr. Fatima Cody Stanford. It has been updated to reflect the findings of a new report. 

Chances are, a doctor has at one point measured your Body Mass Index to check if you are a healthy weight. But a new report suggests that BMI should no longer be used as a measure of an individual's health. 

BMI is calculated using a person's weight and height, and doctors may tell those who fall into the obese or severely obese categories that they could be at risk of health issues including diabetes and cancer. The solution?: Lose weight.

But the report, published in the journal The Lancet Diabetes & Endocrinology on Tuesday, suggested that having obesity according to the BMI scale doesn't mean a person is unhealthy. It comes after the American Medical Association raised similar concerns about BMI in 2023. 

The report includes recommendations from 58 experts in multiple medical specialties and from multiple countries, as well as input from two people with lived experience of obesity.

The experts concluded that people should be diagnosed with "clinical obesity" if their weight negatively affects their organs or they struggle with daily activities. If patients have excess fat but no health problems, they should be diagnosed with "preclinical obesity," and not be treated for their fat levels.

The report also recommended using other measurements instead of BMI to determine if a person has obesity.

"It doesn't tell you anything about the health of a person," Dr. Fatima Cody Stanford, an obesity medicine physician and associate professor of medicine and pediatrics at Harvard Medical School, previously told Business Insider.

Here's why BMI is a bogus way to evaluate your health and what you should be paying attention to instead, according to experts who spoke to BI in 2022 and prior, before 2025 Lancet report was published. 

Higher weight is not a death sentence

Having a higher body weight increases the risk of developing a life-altering disease such as diabetes or high-blood pressure, but not everyone who has excess body fat has "significant disease," Stanford said.

The problem with BMI is that it puts too much emphasis on a target weight, which can be misleading.

Stanford recalls the case of a patient who weighed 550 pounds and had obstructive sleep apnea and low testosterone levels, in spite of an active lifestyle.

He reduced his weight to 300 pounds, and no longer had any health problems caused by severe obesity, she said, despite his BMI still being "very high."

BMI is an arbitrary and outdated metric

When BMI was created, it had nothing to do with health. 

Albert Quetelet, an astronomer and sociologist, first defined a metric relating weight to height squared in the 1830s, and this later formed the basis of BMI. Originally, it was meant to help describe the dimensions of the "perfect" or average man.

Quetelet only looked at white French and Belgian men, a very narrow representation of humanity. His ideas were later used to justify racist and eugenic policies and have been discredited. 

Quetelet never intended the ratio to be linked to health. That came in the 1900s when the Metropolitan Life Insurance Company used Quetelet's formula to build actuarial tables based on height and weight, and used data from their mostly white policyholders.

So the metric is deeply biased, and was only designed to measure your risk of dying if you're white, said Stanford.

Studies, including one led by Stanford, have shown that Black and Asian people may not be at the same risk as white people with the same BMI. 

Waist size is a better predictor of ill health — but still isn't perfect

The 2025 report suggested that health is much more complicated and individual than BMI can show.

"Where we carry our adipose or fat is much more important than how much fat we have," Stanford said.

That's because not all fat cells are created equal. Fat that wraps around internal organs is much more likely to lead to disease, but fat around the hips may have a protective effect against heart disease, for instance, Stanford said.

Plus, BMI doesn't take into account the differences between fat and muscle, or differences in fat distribution among different ethnicities, the report said.

So while BMI can be useful when studying the health of a population, the authors of the report recommended that other measurements be used to assess individual patients' health, such as a direct measurement of body fat or waist-to-hip ratio. 

Stanford said that waist size is a reliable measure of weight-related health risk.

Women with a waist size over 35 inches and men with a waist larger than 40 inches are at higher risk of developing metabolic diseases, she said. 

Regardless, without other measures of ill health — such as blood pressure, fasting blood sugar, or cholesterol, insulin, and testosterone levels — it is very difficult to tell if a person is unhealthy, said Stanford.

What if your doctor only looks at BMI? 

Some doctors will use BMI to assume ill health and prescribe weight loss, Stanford said.  

Stanford advises patients whose doctor only focuses on BMI to challenge them.

"Say: 'Okay doctor, I hear that. And I do see that BMI does exceed these guidelines, but how does this relate to my current health status?', which will probably challenge them because they've only thought to think of it in terms of BMI," she said.  

The recommendations made in the report were endorsed by 76 organizations worldwide, including scientific societies and patient advocacy groups.

Erin Brodwin contributed reporting to a previous version of this article.