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BMI vs. Body Composition

We’ve all hopped off the scale feeling a little disappointed with the results, but nothing compares to the displeasure of being told your BMI at the doctor’s office. BMI, or body mass index, is a popular scale for estimating the amount of body fat you have based on your height and weight. While it can be accurate at times, BMI doesn’t give you a full picture of what your body weight comprises. This is where body composition analysis comes to the rescue. Let’s take a deeper look at the differences between BMI and body composition so you can determine which method is better for tracking your fitness progress.


What is BMI?

Body Mass Index (BMI) is something you’ve probably discussed, albeit reluctantly, with your doctor at some point during your regular checkups. BMI is the most popular choice in clinical settings because it’s good at helping to predict a person’s health based on certain population trends.

To calculate your BMI, you simply take your weight in kilograms and divide it by your height in square meters. Then, you take your score and see where it falls on the BMI scale to see which category you’re in—underweight, healthy weight, overweight, or obese (Source: CDC).

Generally, if your BMI is below 18.5, you are classified as underweight. A score of 18.5 to 24.9 is considered a healthy weight, 25 to 29.9 indicates someone is overweight, and then a score of 30 and above is classified as obese. However, the problem with BMI is that it doesn’t actually measure your body’s fat or muscle content and is only an estimate. It completely overlooks the fact that two people with the same weight and height may look distinctly different based on their body composition (Source: CDC). This is especially true for more athletic people, as you’ve probably heard that muscle weights more than fat—which is true!

So, although it’s often correlated with other methods of measuring body fat and a person’s risks of metabolic diseases, it’s still not the best option when it comes to seeing how your body is changing due to your workouts.


What is Body Composition?

Body composition analysis is another popular method for measuring weight—particularly the breakdown of fat, muscle, bone, and water content within your body. There are multiple methods of assessing body composition, including skinfold measurements and hydrostatic weighing, but the most popular option is bio-electrical impedance analysis (BIA). BIA estimates body fat percentages by sending weak electrical currents through the body and measuring the voltage based on the resistance given by different tissues, with muscle and water giving lower readings.

This is the technology we utilize within local 9Round studios that offer InBody scans to help you track your progress. BIA provides a solid baseline for you to measure your fitness progress against as you continue working out, so you can see the changes in fat and muscle content over time. Not only will this tell you how much fat you need to lose or how much muscle you need to gain, but it can also help you stay motivated by showing you the changes your workouts are making, even when the number on your bathroom scale isn’t moving.

A typical body fat composition for a healthy individual should fall between 10-20 percent for men and 18-28 percent for women (Inbody USA). The lower your body fat percentage, the more athletic you are considered. The threshold for being classified as overweight based on your body composition is 21-24 percent body fat for men and 31-36 percent for women. Over 24 percent body fat for men and over 38 percent for women is considered obese. 


So, which one is better?

Based on the information above, you can see that both BMI and body composition offer good insight into your overall health. BMI is great for understanding your general weight category and finding a starting point to track your progress. However, if you want to see how your workouts are changing your body over time, body composition is the way to go. This method of measuring progress offers a clearer and more accurate picture of where you are and where you’re headed with your fitness journey by showing an actual breakdown of fat and muscle content.


If you’re curious about how you can start shedding fat and building lean muscle, then come try 9Round’s revolutionary kickboxing-themed workouts with a complimentary session. Sign up for your preferred time below and get ready to kick your fitness up a notch with our triple-threat approach to wellness. We can’t wait to show you the power of kickboxing fitness! 

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