BMI: Not an Accurate Measure of Health Nor Obesity
A Popular Health Measurement Isn't So Accurate
If you’ve ever had a routine doctor’s visit or signed up for health insurance, your BMI was probably checked. It’s often used in check-ups to categorize weight as “underweight,” “normal,” “overweight,” or “obese.”
Most healthcare providers use BMI to estimate whether your weight is healthy or not. You might have even tracked your BMI as part of your health goals—I know I did! For years, I watched my weight, hoping to lower my BMI.
With 40% of the U.S. population classified as obese, it’s hard not to worry about your BMI—especially since obesity is linked to many health risks.
And because BMI is a fast and simple calculation, it’s become a popular self-check for many of us.
But BMI is far from perfect and may not reflect your true health.
Experts have criticized BMI for a long time. On June 14, 2023, the American Medical Association (AMA)—the largest group of doctors in the U.S.—urged physicians to stop relying on BMI alone to measure health.
Earlier this year, a group of global experts also suggested redefining obesity beyond BMI alone. Their report calls BMI outdated and says we need a better way to measure body fat and overall health.
What Is BMI?
Body mass index, or BMI, is calculated by dividing your weight in kilograms by your height in meters squared.
Your BMI score places you in categories: underweight (below 18.5), overweight (above 25), and obese (above 30). Obesity is further divided into three classes, with higher numbers showing more severe obesity.
What makes BMI so popular is how easy it is to calculate—it’s quick, low-cost, and can even be done at home.
You can plug your weight and height into online calculators, like the adult BMI calculator provided by the Centers for Disease Control and Prevention (CDC), and instantly get your classification.
But just because it’s easy doesn’t mean it’s accurate.
What’s the Issue With BMI?
Obesity is a medical condition where too much fat builds up in the body.
As AMA noted, the biggest problem with BMI is that it doesn’t directly measure body fat—it only uses weight and height as proxies, which can be misleading.
For example, a muscular person with very little fat could have the same BMI as someone with obesity. Athletes, who are in top shape, may be labeled overweight or obese under BMI standards.
Studies also show that linking weight to health outcomes is inconsistent. The widely held belief that a higher weight always equals poor health simply isn’t accurate.
BMI’s roots also reveal its flaws. It was invented 200 years ago by a Belgian astronomer and based on data from European white men. It doesn’t account for how body fat distribution varies by age, sex, or ethnicity.
A 2016 study found that 54 million Americans labeled overweight or obese by BMI were actually metabolically healthy, Meanwhile, 21 million with a “normal” BMI were unhealthy.
Similarly, BMI often mislabel Black people as overweight while missing health risks in Asians who may have lower BMIs but higher disease risks.
Why BMI Can Cause Harm?
Here’s what many don’t realize: focusing too much on BMI can actually do more harm than good.
Weight-based shame—often fueled by BMI checks—can stop people from seeking medical care.
Case in point: A study found that about 2 in 3 women with severe obesity delayed seeking healthcare because of their weight. More than 4 in 5 felt it was a barrier to getting proper care.
While the scales didn’t stop me from having myself checked, I’ve always dreaded weight checks, whether at the doctor’s office or even at home.
For years, that number on the scale felt like the ultimate judgment of my health and self-worth.
It’s a relief to learn that being heavy isn’t immediately bad as long as I’m healthy.
What to Note
Despite its flaws, experts aren’t saying we should completely get rid of BMI, It’s still a great screening tool. But it should be just one part of the equation, not the whole story.
Those classified as obese using BMI might need extra tests to get a fuller picture of their health. Waist-to-hip ratios or waist-to-height ratios may give a better idea of body fat levels.
For example, researchers suggest that women with a waist over 34.6 inches or men with a waist over 40 inches likely have excess body fat, no matter their BMI.
The new criteria also propose reclassifying some cases:
People with a BMI of 25 or higher but no health issues would be labeled as having “preclinical obesity” and monitored to avoid weight gain.
Those with a BMI of 40 or higher could still be diagnosed with obesity based solely on BMI.
These changes aren’t official yeat, so it’s unclear how quickly they’ll be adopted. While it may add work for doctors, the shift could give patients a more accurate view of their health. And that’s worth it.
What Does This Mean for You?
So what does all this mean for us? It’s time to stop obsessing over the “ideal weight” or a “perfect BMI.” Instead, we should focus on what really matters—living a healthy, balanced life.
BMI is just one number—it doesn’t define you or your health. Let’s stop viewing higher weight as a stigma and start focusing on habits that truly make you feel your best.
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