What you’ll learn
We’ll break down how to calculate BMI and why it’s often misleading when used on its own. You’ll learn what body fat percentage really tells you about your health, the tools available to measure it (like smart scales and DEXA scans). We’ll also explore how treatments like GLP-1 medications can support lasting, healthy weight loss when body composition matters most.
Have you heard of BMI, or Body Mass Index? It’s a number that claims to tell you whether you’re underweight, overweight, or “just right.” Has it ever made you feel judged, frustrated, or confused?
Here’s the thing: BMI doesn’t actually measure body fat. It’s a basic math formula based on your height and weight. That’s it. It doesn’t account for muscle, fat distribution, or how active you are in your everyday life.
And because of that, BMI can be wildly misleading. This is why someone with a high body fat percentage, like a muscular athlete, can be labeled “obese,” while someone with very low muscle mass and high fat (the so-called “skinny fat” body type) can fall in the “normal” range.
At QuickMD, our team of licensed providers regularly works with patients who are confused or frustrated by their BMI scores. We’ve seen firsthand how a number that was meant to be simple has turned into something that often misleads more than it helps.
That’s why we believe it’s important to give you the facts and explain what your body is really telling you, not just what a chart says.
There’s a better way to understand your health: body fat percentage. This actually shows what your body is made of, helping you understand what constitutes a good body fat percentage: how much of it is fat and how much is lean mass (like muscle, bone, and water). It gives a far more accurate picture of your fitness, your risks, and your goals.
In this article, we’ll explain how BMI is calculated, why body fat percentage is often a better marker of health, and how you can measure it accurately. We’ll also explore examples like the “skinny fat” body type and the pitfalls of relying solely on weight.
And if your goal is to lower your fat percentage while protecting muscle, especially if you’ve struggled with weight in the past, we’ll briefly introduce a newer class of medications called GLP-1 (glucagon-like peptide-1) receptor agonists, which patients are now using as part of a medically guided fat loss plan.
These aren’t for everyone, but they’ve opened the door to safer, more sustainable results when used responsibly and under medical care.
Let’s start by breaking down what BMI actually is and why it often doesn’t tell the full story.
What is BMI, and how do you calculate it?
Body Mass Index (BMI) is a formula that uses your weight and height to estimate your overall body size. It’s simple and widely used in clinics, fitness apps, and insurance forms. But it has some serious limitations.
The formula looks like this:
BMI = weight (kg) / height (m²)
If you’re using pounds and inches, you’ll first need to convert:
- 1 kilogram = 2.204 pounds
- 1 meter = 39.37 inches
Let’s say you weigh 150 pounds and are 5’5″ (65 inches).
First, to obtain accurate measurements, convert to metric:
- 150 lbs ÷ 2.204 = 68.06 kg
- 65 inches ÷ 39.37 = 1.65 meters
- Now square the height: 1.65 × 1.65 = 2.72
- Then divide: 68.03 ÷ 2.72 = BMI of 25.0
You can just use any online BMI calculator to plug in the numbers. But keep reading to see why that number you get might not mean what you think.
Here’s how BMI is categorized:
- Underweight: <18.5
- Normal weight: 18.5-24.9
- Overweight: 25-29.9
- Obesity: 30 or greater
At a glance, this might seem helpful. But BMI doesn’t look at body composition, the ratio of fat mass to lean body mass (like muscle and bone). So, two people with the same BMI can have very different health profiles.
That’s why body fat percentage is so important here. It gives you a more accurate look at what’s going on with your body.
What is body fat percentage?
Body fat percentage is exactly what it sounds like: the proportion of your total body weight that comes from fat tissue. Unlike BMI, which only looks at your overall weight relative to height, body fat percentage tells you what your body is actually made of.
When we talk about body composition, we’re essentially dividing your body into two main categories:
- Fat mass: This includes all the fat tissue in your body, from the fat just under your skin (subcutaneous fat) to the fat around your internal organs (visceral fat).
- Lean mass: This is everything else. Your muscles, bones, organs, blood, and water. This is the metabolically active tissue that burns calories even when you’re at rest.
Why body fat percentage gives a clearer picture
Here’s how body fat percentage gives you a better idea of what some of your health metrics actually look like
For example:
- Healthy body fat percentages for women generally fall within a healthy range of 21-33%, depending on age.
- For men, a healthy range is typically around 8-24%.
This is really helpful if you’re on top of your health, as knowing your body fat percentage helps provide a more complete picture of your overall health than BMI alone.
A higher percentage of visceral fat can increase your risk of diabetes, cardiovascular disease, and inflammation, even if your BMI is normal. To show you exactly why this matters, let’s look at two examples where BMI gets it wrong.
Why BMI can be misleading: two examples
Example 1: the muscular “overweight” bodybuilder
Let’s say we have a man who’s 5’10” and weighs 220 pounds.
His BMI comes out to 31.6, which falls squarely in the obese category. But here’s the thing: this person has just 10% body fat, a level typically seen in athletes and bodybuilders. The rest of his weight comes from muscle mass, not fat.
In reality, he’s likely in excellent physical health. But if you go by BMI alone, he’d be flagged as high-risk, which could affect his insurance premiums, doctor recommendations, or how his health is judged on paper.
Example 2: the “skinny fat” body type
Now consider a woman who’s 5’3” and weighs 115 pounds.
Her BMI is 20.4, which is considered solidly “normal.” But her body fat percentage is 36%, which is considered a high body fat percentage for women and is well above the recommended range.
She may appear lean, but her low muscle mass and high fat mass could increase her risk for other factors like insulin resistance, heart disease, or poor metabolic health.
This is often called being “skinny fat,” a term used for people who look thin but have a high percentage of body fat and very little muscle tone. It’s an example of how weight alone doesn’t tell the whole story.
These examples show exactly why body composition matters more than just BMI alone. But if BMI isn’t reliable and body fat percentage is what really counts, how do you actually measure it accurately?
How to measure body fat (and which methods are actually reliable)
If BMI isn’t enough, how do you get a better picture of your body composition? There are several methods for body fat measurement that are accurate for assessing body fat percentage, ranging from affordable smart scales to clinical DEXA scans, each with its own pros and cons.
1. DEXA scans (Dual-Energy X-ray Absorptiometry)
This is one of the most accurate ways to assess fat mass, lean mass, and even bone density. You’ll often see them in sports medicine and clinical settings.
A DEXA scan gives a detailed breakdown of where fat is stored in your body, including visceral fat (fat around the organs), which is especially important for assessing health risks.
2. Body fat scales (bioelectrical impedance analysis)
These smart scales send a small electrical current through the body to estimate fat, muscle, and water composition.
They’re widely available, but accuracy can vary depending on hydration, body type, and brand.
- Some are impressively close to clinical results
- Others may produce inconsistent or misleading readings
Still, these can be useful for tracking trends over time, especially if you weigh yourself under consistent conditions.
3. Skinfold calipers
This old-school method involves measuring the thickness of the fat layer just under your skin at specific points on your body using calipers.
For more accurate results, you need proper technique, and it really helps if the same person takes your measurements each time to keep things consistent.
If done correctly (usually by a trained medical professional), it can be pretty accurate. But it does require practice and some expertise.
4. Body circumference measurements
Using body measurements with a tape measure to track waist, hips, and other key points can give a rough sense of fat distribution in a person’s body.
It’s easy and inexpensive, but less precise. Excess fat around the waist, as indicated by these body measurements, can signal increased health risks. This method works best when you use it alongside other tracking tools.
5. Hydrostatic weighing
Once the gold standard, hydrostatic weighing involves submerging the human body in water to calculate body density and composition. This method estimates fat-free mass and body fat percentage, but it’s not very accessible to most people.
The bigger picture: muscle, fat, and health risk
Whether you’re a powerlifter or someone with a naturally smaller frame, body composition (not just body size) matters most regarding long-term health.
High fat mass, especially visceral fat, increases the risk of:
- Insulin resistance
- Heart disease
- Chronic inflammation
- Poor metabolic health
The good news is that understanding where your body stores fat gives you valuable information. Visceral fat tends to be more metabolically active than subcutaneous fat, which is why it gets more attention in health research.
And just because you’re in a “normal” BMI range doesn’t mean you have the full picture. If you’re lower on lean muscle mass and carrying more body fat, it’s worth paying attention to your overall body composition. Building muscle through strength training can also boost your metabolism, helping you burn more calories throughout the day.
If you’ve been doing everything “right” but your body still isn’t responding the way you hoped, that’s not a reflection of your effort or willpower. For many, the struggle runs deeper than diet and exercise.
Next, we’ll explore some solutions that go beyond dieting and why GLP-1 medications might play a role for some people.
GLP-1 medications and body fat
For people struggling to reduce fat through diet and exercise alone, GLP-1 receptor agonists like semaglutide (Ozempic®, Wegovy®) and tirzepatide (Mounjaro®) are emerging as helpful tools to help people lose weight as part of a comprehensive health plan.
Originally developed to treat type 2 diabetes, these medications are now FDA-approved for weight loss in certain individuals.
What makes them different?
GLP-1s help you regulate appetite, digestion, and how your body processes sugar. They can lead to meaningful reductions in body fat percentage, especially visceral fat, while helping you keep or even build lean muscle mass when you’re also eating well and doing strength training.
Now, while losing body fat is often the goal, it’s important to remember that your body needs a certain amount of fat to function properly. This essential body fat supports reproductive functions and overall health, and having too little can negatively impact vital processes.
GLP-1s don’t replace healthy habits, but they can make it easier to maintain those habits, especially if your body tends to resist losing weight or fat loss on its own.
At QuickMD, we offer access to licensed providers who can help you determine whether GLP-1 treatment might be right for your goals. It’s about addressing the biological factors that make losing weight challenging.
Health isn’t just a number
The problem with BMI is that it’s outdated and ultimately misses the full picture of your health.
Two people can have the same BMI and live in very different bodies, with different levels of fat, muscle, strength, and risk. That’s why more people are turning to tools, like GLP-1s, that look beyond the scale to assess body composition, like body fat percentage, lean mass, and overall body composition.
If you’ve been tracking your progress but still feel stuck, it may not be about discipline. Biology plays a huge role in how your body stores fat, responds to hunger, and loses weight. And for many, even consistent lifestyle changes aren’t enough to move the needle in a lasting way.
That’s where GLP-1 medications come in. These treatments are helping people safely reduce body fat, especially visceral fat, while preserving muscle. Backed by clinical research and overseen by medical professionals, they may be an option when diet and exercise alone aren’t enough.
It’s okay to feel discouraged if progress has been slow or invisible. Real health changes take time, support, and often, a more compassionate approach than what most of us were taught.
At QuickMD, our providers take your full health into account, not just your weight. Whether you’re trying to better understand your body composition or exploring GLP-1 options like Ozempic®, Wegovy®, or Mounjaro®, we’re here to help.
Frequently asked questions about BMI and body fat percentage
Does age affect your ideal body fat percentage?
Yes. As you age, natural hormonal changes and muscle loss (called sarcopenia) can increase body fat even if your weight stays the same.
That’s why body fat percentage targets vary by age and sex. For example, a healthy body fat range for a woman in her 20s might be 21-33%, while for a woman in her 50s, 23-35% is considered normal.
Can your genetics influence your body fat distribution?
Genetics play a big role in where your body stores fat.
Some people naturally carry more fat in the hips and thighs, while others store more in the abdominal area, which is linked to a higher risk of chronic disease.
You can’t control your genetics, but you can influence your overall health with consistent habits like strength training and a balanced diet.
How accurate are smart scales for body fat?
Smart scales that use bioelectrical impedance analysis (BIA) can provide a rough estimate of body fat percentage, but their accuracy varies.
Hydration levels, recent meals, and even time of day can affect readings. While helpful for tracking trends over time, they shouldn’t be your only tool for assessing your body composition.
