5 Reasons BMI Is a Terrible Measure of Your Health

Have you ever calculated your body mass index (BMI) online or seen it listed on your doctor’s after-visit summary and thought, “Oh no!” That reaction is understandable. We’ve been conditioned to associate a higher BMI with increased risk for chronic diseases like heart disease and diabetes. So it makes sense that we’d want our BMI to fall into the coveted "normal" range, right?

The truth is, using BMI to assess health on an individual level is not only inaccurate, it’s also problematic and potentially harmful. Let’s look at why—starting with a quick history lesson.

A Brief History

The BMI equation—weight divided by height squared—was first created by a statistician in the 1800s. It was intended to be used to assess body size in large population studies. In other words, it could help us make broad observations about regional differences, disease correlation, and public health strategies.

It wasn’t until the 1970s that BMI began being used to diagnose “obesity.” Soon after, the World Health Organization and the insurance industry adopted this tool as a way to estimate individual disease risk. In the 1990s, when the so-called “global obesity epidemic” was formally recognized, the International Obesity Task Force established the BMI categories we now see everywhere—from classrooms to medical records to weight-loss ads.

But here’s the problem: BMI was never intended to measure individual health, nor was its creator a medical professional. BMI categories are inherently flawed. Here’s how:

1. BMI categories don’t align with research

Many studies have shown that people in the “overweight” BMI category live longer than those in the “normal” category. Even individuals in the moderately “obese” categories live at least as long as those with a “normal” BMI. For older adults and people with heart disease, carrying extra weight may even have a protective effect on survival. In other words, survival rates in these groups are often better above what is currently labeled a “healthy” weight.

2. BMI cutoffs had ulterior motives

If research doesn’t support these BMI cutoffs, why do they exist? The International Obesity Task Force, which helped set these standards, was heavily funded by pharmaceutical companies. Conveniently, this happened around the same time weight-loss drugs like orlistat and Redux were being developed. Lowering the thresholds for “overweight” and “obese” dramatically expanded the market for these medications.

3. BMI fails to account for demographic differences

The original BMI formula was based on “healthy” white European men and still does not adequately account for women, people of color, or varying body types. Body composition differs across genders, ages, and ethnicities while still falling within a range of good health. BMI simply doesn’t reflect this diversity.

4. BMI use in medical settings can do more harm than good

BMI is measured at nearly every medical visit—96% of Medicare visits included it in 2018. It often drives weight-focused interventions, despite little evidence that this improves morbidity or mortality. Instead, it fuels weight stigma, discourages people from seeking care, and shifts focus away from more meaningful health measures.

Additionally, treating a BMI of 25 or higher as a disease state—regardless of other health factors—leads to overdiagnosis of otherwise healthy people. At the same time, serious conditions can be missed in “normal-weight” individuals. The result? Unnecessary and costly health interventions for some, and delayed or inadequate care for others.

5. BMI is a number, not a health behavior

Focusing on BMI or weight assumes these numbers directly represent health and are fully within our control. Neither is true. Our bodies have natural set points, and attempts to override them often lead to disordered eating, excessive exercise, or constant anxiety about food and weight. This pursuit of control can ultimately worsen health rather than improve it.

If not BMI, then what?

There’s no single weight beyond which you are automatically unhealthy. BMI is an unreliable, overly simplistic tool for assessing individual health. It’s time to move beyond arbitrary BMI categories and rethink how we define health.

True health is influenced by genetics, environment, lifestyle, mental and emotional well-being, and culture—not a single number. Instead of focusing on weight or BMI, focus on health behaviors that feel manageable, honor your physical and emotional needs, and improve your quality of life. These kinds of changes are sustainable and, more importantly, achievable without body scrutiny.

I invite you to challenge the narrative that your BMI defines your health. All bodies deserve dignity and respect, and health is possible at every size.

Haley Golich is a Registered Dietitian, Certified Intuitive Eating Counselor, and the owner of Redefine Health. Contact her today to learn more about 1:1 virtual nutrition counseling.

References

https://pmc.ncbi.nlm.nih.gov/articles/PMC9197270/

https://journalofethics.ama-assn.org/article/use-and-misuse-bmi-categories/2023-07

https://pmc.ncbi.nlm.nih.gov/articles/PMC10693914/

https://pmc.ncbi.nlm.nih.gov/articles/PMC3920805/