For decades, Body Mass Index (BMI) has been one of the most commonly used tools for determining whether someone falls into an underweight, healthy weight, overweight, or obese category.
The calculation is simple: BMI compares your weight to your height.
But here's the problem: your weight doesn't tell us what your weight is made of.
Two people can have exactly the same height and weight—and therefore the same BMI—while having very different amounts of muscle, body fat, visceral fat, bone mass, and very different metabolic health.
So, while BMI can provide useful information, particularly when looking at large populations, it should not be the only number we use to define an individual's health.
What Does BMI Actually Measure?
BMI is calculated using this formula:
BMI = weight (kg) ÷ height (m)²
For adults, the traditional classifications are:
Underweight: Below 18.5
Healthy weight: 18.5–24.9
Overweight: 25.0–29.9
Obesity: 30.0 and above
BMI is inexpensive, quick, and easy to calculate, which is one reason it has been used for so long.
But BMI does not directly measure body fat.
It cannot distinguish between:
• Muscle and fat
• Visceral fat and subcutaneous fat
• Bone mass
• Differences in body composition
• Where fat is stored in the body
Imagine two people who are both 5'10" and weigh 190 pounds.
One may be a muscular athlete with relatively low body fat. The other may have significantly less muscle and carry more fat around the abdomen.
Their BMI could be identical, yet their health profiles could be very different.
This is why the CDC describes BMI as a screening measure, not a complete assessment of an individual's health. More recent research has also emphasized the importance of assessing actual adiposity and fat distribution rather than relying exclusively on BMI.
Where We Carry Fat Matters
One important piece BMI misses is where fat is stored.
Visceral fat—the fat stored deeper in the abdomen around internal organs—is particularly important because excess visceral fat is associated with insulin resistance and increased cardiometabolic risk.
That means someone can have a BMI within the "normal" range and still carry excess abdominal fat and have metabolic abnormalities.
Conversely, someone with a BMI in the "overweight" category may be physically active, muscular, have a healthy waist circumference, normal blood pressure, healthy blood glucose and lipids, and relatively low body fat.
Instead of focusing on BMI alone, we can look at a broader picture that includes:
Waist circumference
Body composition/body-fat percentage
Blood pressure
Fasting glucose and A1C
Triglycerides and cholesterol
Physical fitness and strength
Sleep and lifestyle habits
BMI can be one piece of the puzzle—it simply shouldn't be the entire puzzle.
Obesity Has Increased Dramatically
Even with the limitations of BMI, there is no question that excess body fat and obesity have become major public-health concerns in the United States.
CDC data show that adult obesity prevalence, as defined by BMI, increased from 30.5% in 1999–2000 to 41.9% in 2017–March 2020. Severe obesity increased from 4.7% to 9.2% during the same period.
Today, nearly 3 out of every 4 American adults have overweight or obesity when classified using BMI.
How did we get here?
There isn't one simple answer.
Obesity Is More Than "Eating Too Much"
Weight regulation is complicated.
Our genetics haven't suddenly changed over the last several decades, but our environment and lifestyles certainly have.
We live in a world where highly processed, calorie-dense foods are readily available. Portions have grown. Sugary drinks are everywhere. Many jobs require sitting for hours. We drive instead of walk. Screens occupy increasing amounts of our time. Many people aren't sleeping enough, and chronic stress has become part of everyday life.
Access matters, too. Not everyone has equal access to affordable nutritious foods, safe places to exercise, adequate health care, or enough time and resources to prepare meals.
And there are additional factors.
Genetics can influence susceptibility to weight gain. Certain medical conditions and medications can contribute. Poor sleep can alter hormones involved in appetite and energy regulation. Stress can affect eating behavior and metabolic health.
Obesity therefore isn't simply a matter of willpower.
It develops through a complex interaction between biology, behavior, environment, genetics, sleep, stress, medications, food availability, and physical activity.
Why Does Excess Body Fat Matter?
The goal shouldn't simply be to become smaller.
The bigger concern is what excess adipose tissue—particularly visceral fat—can do metabolically.
Excess body fat is associated with increased risk of numerous chronic conditions, including:
• Insulin resistance and type 2 diabetes
• High blood pressure
• Cardiovascular disease
• Stroke
• Metabolic dysfunction-associated fatty liver disease
• Abnormal cholesterol and triglycerides
• Sleep apnea and other breathing problems
• Osteoarthritis and joint problems
• Kidney disease
• Gallbladder disease
• Certain cancers
This is another reason I prefer to look beyond the scale.
The question isn't simply:
"How much do you weigh?"
A better question is:
"What is happening metabolically inside your body?"
Simple Changes Can Make a Big Difference
The good news is that improving metabolic health doesn't require perfection.
It starts with consistently making better choices.
1. Build Your Meals Around Whole Foods
Make vegetables, fruits, legumes, whole grains, nuts and seeds the foundation of your diet.
Whole plant foods naturally provide fiber, vitamins, minerals, phytonutrients and other compounds that support metabolic and cardiovascular health.
Instead of obsessing over calories, begin by asking:
"How much nutrition am I getting from the food I'm eating?"
2. Increase Your Fiber
Fiber helps with satiety, blood-sugar regulation, cholesterol management and gut health.
Beans, lentils, vegetables, fruits, oats, barley, whole grains, chia and flax are excellent sources.
And remember—most fiber is found in plants.
3. Reduce Highly Processed Foods
You don't need to eat perfectly.
But regularly consuming foods high in added sugars, refined carbohydrates and calories while providing relatively little fiber can make it easier to consume more energy than your body needs.
Focus on replacing rather than simply restricting.
Add the apple.
Add the vegetables.
Add the beans.
Add the whole grains.
Add the water.
As you add more nutrient-dense foods, there is naturally less room for foods that aren't serving your health.
4. Move Your Body Every Day
Exercise isn't just about burning calories.
Physical activity improves insulin sensitivity, cardiovascular health, mobility, mood and overall metabolic function.
Walk.
Bike.
Hike.
Dance.
Garden.
And don't forget strength training.
Building and maintaining skeletal muscle becomes increasingly important as we age because muscle is metabolically active tissue and plays an important role in glucose disposal, physical function and healthy aging.
5. Prioritize Sleep
Sleep is often the forgotten component of metabolic health.
Insufficient or poor-quality sleep can influence hunger, appetite and weight regulation.
For most adults, aiming for at least seven hours of quality sleep is an important part of a healthy lifestyle.
6. Manage Stress
We can't eliminate every source of stress, but we can change how we respond to it.
Walking, exercise, meditation, breathing exercises, time outdoors, meaningful relationships and simply taking time away from screens can all help support our nervous system.
7. Measure Health Beyond the Scale
Instead of letting one number determine how you feel about your health, look at the bigger picture.
Ask yourself:
Is my waist circumference improving?
Am I getting stronger?
Is my blood pressure healthy?
Are my fasting glucose and A1C improving?
Are my triglycerides improving?
Am I sleeping better?
Do I have more energy?
Can I walk farther?
Do I feel better?
Those are meaningful measures of progress.
Health Is Bigger Than BMI
BMI isn't necessarily a "bad" measurement. It is simply an incomplete measurement.
It can help identify trends across large populations and serve as an initial screening tool. But when we are evaluating an individual, we need to look beyond height and weight.
We need to consider body composition, abdominal fat, laboratory values, physical fitness, lifestyle habits, medical history and overall metabolic health.
Most importantly, we need to move away from the idea that health is determined by achieving a particular number on a scale.
The goal isn't simply weight loss. The goal is better health.
Small choices made consistently—choosing whole foods, moving your body, building muscle, sleeping well, managing stress and understanding your health markers—can add up to profound changes over time.
Your body is constantly giving you information.
The more you understand that information, the more empowered you become to take care of it.
Health is not one number. It is the accumulation of the choices we make every day.
To Health & Longevity, 🌿
Innovative Wellness
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References
Centers for Disease Control and Prevention. About Body Mass Index (BMI). CDC, updated December 16, 2025.
Centers for Disease Control and Prevention. Adult Obesity Facts. CDC.
National Institute of Diabetes and Digestive and Kidney Diseases. Understanding Adult Overweight & Obesity. National Institutes of Health.