Have you ever compared your body to your best friend’s body? You may wonder how your best friend is tall and thin and you are short and round, but you weigh the exact same. How can that be? How can two people, same gender, look completely different but weigh the same? That’s because humans all have different body compositions.  

What is Body Composition?

It’s best described as what bodies are made of. Human bodies are made up of varying percentages of water, fat, bone and muscle. Don’t let body composition be confused with body mass index (BMI). Body mass index is a measurement of weight-for-height.   

When you step on a scale, the number tells you how much you weigh, but it doesn’t tell you what your body is made up of. Body composition refers to everything in your body and how much you have of each component. For example, a person’s body could be composed of 36% muscle, 12% essential fat, 15% non-essential fat, 12% bone and 25% other (organs, etc.) Let’s take this breakdown and work our way up to make it easier to understand, taking the five example percentages and putting them into two groups; fat mass and fat-free mass1 

>> Fat mass refers to fat tissue in your body and fat-free mass includes everything else (like muscle, bone, fluid and organs) 

What the Scale Really Tells You

Stepping on the scale will show you one number, your weight. What you don’t see are the other numbers in your body and how they affect your body composition.  

For example, if you start an exercise program you may gain one pound of muscle and lose one pound of fat. Since your fat mass decreased and your fat-free mass increased at the same time, your body weight won’t change. See how frustrating this can be for someone who thinks they are putting in a lot of effort at the gym and eating healthy but not seeing the weight change on the scale? This is why the scale is misleading and that’s why knowing your body composition is much more useful than knowing your body weight.

How to Measure Body Composition

Track with a Tape Measure

So, what can you use to measure your body composition? The first way would be to track and measure different body parts2. Purchase a flexible tape measure and track the circumference of your waist, hips, arms, legs and chest.

If you track your measurements for a period of six months, for example, and your waist circumference decreases, it’s a sign that you are probably losing belly fat. Here’s another example: if your exercise program involves weights and your arm circumference is increasing, it’s a sign that you are probably gaining muscle in your arms. The second way to track your body composition would be to take pictures.  

Track with Images

Progress pictures are a very popular way to physically see the changes in your body over time. These pictures are typically known as ‘transformation pictures’ and can be very helpful when looking at your body composition. We often do not notice changes in our body from day to day, but we do notice changes in our body when looking at progress pictures.

There are devices that measure body composition, like a bioelectrical impedance analysis (BIA). BIA sends small electrical currents through your body to see how much the body resists the current. This information is used to predict your body fat percentage3 but these devices are not always accurate.  

If you’re interested in knowing your body fat mass percentage, have an LA Fitness ProResults® Trainer help you. A ProResults® trainer can help you with basic principles of physical activity and nutrition to help you improve your body composition.  

A Quick Recap

It’s nothing new; exercise and good nutrition are critical for improving body composition. Exercise and weight training help with fat loss and increased muscle mass. Stepping on the scale will only tell you how much you weigh but there are other factors that need to be considered, like age and genetics. Before you start an exercise and nutrition program, please consult your doctor.  

What’s the bottom line? We are all different. No two people are the same, therefore, we all lose and gain (fat, muscle or both) differently. Don’t just step on the scale. The best ways to track body composition is by measuring the circumference of different body parts and taking progress pictures. Grab a notebook and write down your measurements and take your pictures at regular intervals. Give yourself patience and time to see changes.  

If you would like to learn more about Body Mass Index (BMI) and the difference between BMI and Body Composition, you can read about it here 


  1. PubMed Central. National Institutes of Health. Application of standards and models in body composition analysis. November 2015 
  2. PubMed Central. National Institutes of Health. Reference values for body composition and anthropometric measurements in athletes. May 2014
  3. PubMed Central. National Institutes of Health. Bioelectrical impedance analysis–part I: review of principles and methods. October 2004 



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