Value comparison
BMI vs. percent body fat
Short answer
BMI is a ratio of weight to height that says nothing about body composition, while percent body fat tells you how much of that weight is actually fat.
Side by side
| Aspect | BMIBMI | Percent body fatPBF |
|---|---|---|
| What it measures | Weight relative to height squared. It describes how much you weigh for your frame, not what that weight consists of. | The share of fat mass in total weight, in percent. It describes what that weight consists of. |
| How it is produced | Calculated from two inputs: BMI = weight / height². It needs no impedance measurement at all. | Calculated from fat mass and weight: PBF = (fat mass / weight) × 100. Fat mass comes from the impedance measurement. |
| Unit | kg/m² | % |
| Manufacturer reference range | Ideal value 22 (men) and 21 (women); WHO range 18.5–24.9 for both sexes, Asian criteria 18.5–22.9. | Ideal value 15 % (men) and 23 % (women); the "Normal" band is 10–20 % for men and 18–28 % for women. |
| Where on the sheet | Obesity Analysis section, first bar. | Obesity Analysis section, second bar; fat mass in kg also appears in Body Composition Analysis. |
| When to use it | As a rough population-level classification, or on forms where nothing better is available. | Whenever the question is whether fat, muscle or water changed — so in practice whenever you have an InBody result. |
| What it cannot tell you | It cannot separate muscle from fat or say where fat sits; for trained people it reads misleadingly high. | It cannot tell you where the fat is. Distribution is covered by visceral fat area and the segmental analysis. |
When the values diverge
- Muscular type: BMI lands above the range while percent body fat sits inside it. The InBody manual names this combination the muscular type — obese by appearance, muscular in reality.
- Skinny fat (sarcopenic obesity): BMI is normal but percent body fat is above the range. The weight is low; the ratio of muscle to fat inside it is not.
- Older adults losing muscle: weight and BMI can stay flat for years while muscle drops and fat rises. Only percent body fat shows that shift.
- During weight loss: BMI falls with every kilogram regardless of its source, while percent body fat only falls when the loss is actually fat rather than muscle and water.
The most common wrong conclusion
Reading a normal BMI as proof that body composition is fine. BMI cannot separate muscle from fat — that question is answered by percent body fat, not by a weight-to-height ratio.
Full explanations of each value
Related articles
An InBody measurement is not a diagnostic tool. Results do not determine health status and do not replace a medical examination.
FAQ
Frequently asked questions
Why is my BMI above the range when my body fat is normal?
Because BMI only uses weight and height. Muscle weighs more than the same volume of fat, so a trained person reads as obese by BMI while percent body fat stays in the normal band. The InBody manual lists exactly this combination as the muscular type.
If my BMI is normal, can I ignore percent body fat?
No. A normal BMI combined with high percent body fat is precisely what InBody describes as sarcopenic obesity, and weight alone will never reveal it. That is why both values sit side by side on the sheet.
Which of the two moves faster?
Both respond to a change in weight, but percent body fat also moves when the ratio of muscle to fat shifts at the same weight. During body recomposition BMI stays flat while percent body fat falls.
Explanations make the most sense alongside your own trend.
The public guide is open to everyone. The client portal adds your own value, history and the context of a specific measurement.