Why BMI Is Flawed (and What Actually Matters for Health)
For decades, Body Mass Index (BMI) has been used as a quick way to label people’s health status. You’ve probably had your BMI calculated at a doctor’s office or seen it used in the news as a marker of “healthy weight.”
But what is BMI, exactly?
BMI is a simple formula that divides a person’s weight (in kilograms) by their height (in meters squared). Based on the result, people are placed into categories:
- Underweight (below 18.5)
- “Normal weight” (18.5 – 24.9)
- Overweight (25 – 29.9)
- Obese (30 and above)
On paper, this looks straightforward. But in real life, it often doesn’t reflect someone’s actual health. For example, a professional basketball player with a muscular build may land in the “obese” category—even though their blood pressure, cholesterol, and overall fitness are excellent. On the flip side, someone in the “normal weight” range could have elevated blood sugar or high cholesterol that BMI alone doesn’t capture.
I’ve seen this play out with clients in my own practice. One person came to me after their doctor told them they were “unhealthy” because their BMI put them in the “overweight” range. Yet, their labs, energy levels, and lifestyle habits were all excellent—they ate a variety of foods, moved their body regularly, and slept well. The only thing “wrong” was the number on the BMI chart. Understandably, this left them feeling frustrated and discouraged.
And that’s the problem: BMI is flawed. It was never designed to measure individual health, and relying on it can lead to misdiagnoses, shame, and stigma. Let’s take a closer look at why BMI is flawed—and what we should be paying attention to instead.
Why BMI Is Flawed as a Measure of Health
The History of BMI and Why It Doesn’t Work for Individuals
BMI was created almost 200 years ago by a Belgian mathematician, Adolphe Quetelet. His goal? To study averages in large populations—not to evaluate personal health. Despite this, BMI somehow became a cornerstone in medicine and insurance, even though it was never meant to guide care for individuals. That history alone shows why BMI is flawed as a modern health tool.
Why BMI Is Flawed: It Is Rooted in Racism
BMI was developed using data from white European men and then applied universally across all genders and ethnicities. This means it completely ignored the natural diversity of body shapes and sizes among women, people of color, and non-European populations. Later, insurance companies adopted BMI to assess “risk,” reinforcing racial and gender bias in medical and financial systems. Sabrina Strings’ book, “Fearing the Black Body” does an amazing job of discussing this topic.
When we use BMI as the standard of health today, we’re still relying on a tool that was built on exclusion and designed without the input—or representation—of most of the world’s population. That’s a powerful reason why BMI is flawed and why it continues to perpetuate harm.
Why BMI Is Flawed: It Ignores Body Composition
BMI is simply a ratio of height to weight. It doesn’t tell us how much of that weight comes from fat, muscle, bone, or water. For example, athletes with significant muscle mass often fall into the “overweight” or “obese” categories, even when their health markers are excellent. This one-size-fits-all approach is another reason why BMI is flawed.
Why BMI Is Flawed: It Overlooks Diversity and Genetics
Bodies come in countless shapes and sizes influenced by genetics, ethnicity, sex, and age. Yet BMI applies the same cutoffs to everyone. Research shows these cutoffs don’t accurately predict health risk across different populations. This lack of nuance is a clear example of why BMI is flawed and outdated.
Why BMI Is Flawed: Behaviors Matter More Than Numbers
BMI doesn’t tell us anything about how someone lives their life. It doesn’t reflect how you nourish your body with food, engage in joyful movement, sleep well, or manage stress. These day-to-day behaviors have far more impact on health than a BMI category ever could. That’s another reason why BMI is flawed: it overlooks the factors that actually matter.
Why BMI Is Flawed: Weight Stigma Makes Things Worse
Perhaps one of the most harmful effects of BMI is the stigma it reinforces. When BMI is used as the main health indicator, people in larger bodies often face judgment, bias, and even inadequate medical care. Research shows weight stigma itself is linked to higher stress, avoidance of medical care, and worse health outcomes—independent of body size. This is a powerful example of why BMI is flawed and even harmful.
If Not BMI, Then What? Better Indicators of Health
Health is multi-dimensional. No single number can capture it, and certainly not a formula like BMI. Instead, here are better, more meaningful indicators of health that reflect the whole person:
1. Health Behaviors
What we do on a regular basis says far more about our well-being than a chart. Some key behaviors include:
- Eating patterns: Are you eating in a way that fuels your body, brings you satisfaction, and supports your energy throughout the day?
- Movement: Are you moving in ways that feel good, whether that’s walking, dancing, stretching, or playing with your kids—not because you “have to,” but because it supports your well-being?
- Sleep: Are you getting enough rest and waking up refreshed most days?
- Stress management: Do you have tools (like deep breathing, journaling, connection, or downtime) to help navigate life’s inevitable stress?
These behaviors are flexible and can be adjusted to fit your lifestyle, unlike BMI which tells you nothing about how you live.
2. Body Signals and Internal Cues
Our bodies constantly give us feedback—and learning to listen is a much more useful measure of health than an outside number. Indicators include:
- Hunger and fullness: Are you able to recognize when you’re hungry and stop when you’re comfortably full?
- Energy: Do you have consistent energy to get through your day, without constant fatigue or crashes?
- Satisfaction: Are you able to enjoy your meals and feel content afterward, instead of deprived or guilty?
- Resilience: Do you notice that your body can bounce back from stress, movement, or changes in routine?
When these cues are in balance, it’s a strong sign your body is getting what it needs.
3. Quality of Life
Health is not just physical—it’s about being able to live fully. Ask yourself:
- Do I have the energy and freedom to do the things that matter most to me?
- Am I able to enjoy social gatherings, hobbies, or family time without being held back by rigid food rules or constant body concerns?
- Do I feel connected to my body, rather than at war with it?
If your lifestyle supports connection, joy, and meaning, that’s a far stronger marker of well-being than your BMI.
4. Clinical Markers (When Needed)
Sometimes, lab work can provide valuable insight into health. These include:
- Blood pressure
- Blood sugar / A1C
- Cholesterol and triglycerides
- Inflammation markers
Unlike BMI, which is just a calculation, these markers actually measure what’s happening inside your body. They can help guide care without making assumptions based solely on size.
The Bigger Picture
When we shift the focus away from BMI and toward behaviors, internal cues, quality of life, and (when relevant) clinical markers, we gain a much clearer and more compassionate understanding of health. These measures respect body diversity, honor lived experience, and encourage sustainable, supportive habits—rather than shame or restriction.
The Takeaway
When you look at the evidence, it’s clear why BMI is flawed: it’s a simplistic measure rooted in racism, built on limited data, and misapplied across diverse populations. It ignores body diversity, misclassifies health risks, overlooks meaningful behaviors, and can reinforce harmful stigma.
True health isn’t about a number on a chart—it’s about how you live, how you feel, and how you care for your body. By focusing on behaviors, well-being, and self-compassion, we can build a much more accurate—and humane—picture of health.
I often remind my clients of this: you are more than a number. Your health story can’t be summed up by BMI, a scale, or a category. What truly matters is whether you feel supported, nourished, and able to live the life you want in the body you have today.
I am truly passionate about supporting people in caring for their body and improving their health without centering weight or BMI. Reach out to me here if you’d like to find out how we could work together!
