Understanding Body Composition. Why you shouldn’t just trust the scale.

Feb 15, 2019

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You’ve been training and following a strict nutrition plan for an entire month and seeing steady results on the scale; it’s weigh-in day once again. You step on the scale and expect another dramatic change in your weight…only to find out that you weigh exactly the same as the week before! You get discouraged by these numbers and say to yourself, “What’s the point of busting my ass in the gym and cutting all the good stuff from my diet?” You eventually stray from your diet and exercise plan in defeat.

So many times this happens to those who are either trying to lose weight or gain muscle mass, when only taking their weight into consideration to measure success. What needs to be examined is what your body is made of, just because the scale didn’t move, does not necessarily mean that you haven’t made any progress. As long as you’ve continued to train hard in the gym and stuck with your diet, you have like shifted around your body fat and muscle mass simultaneously. This is where understanding body composition is extremely important.

For example, there are two men; both are 6’ tall, weighing 210 lbs. One man is clearly athletic, in-shape, and has a great physique. The other man is visibly out-of-shape and overweight. If both men only went by the weight on the scale, they would be at an even tie. However, with body composition they are extremely different.


So what is body composition?

The human body is comprised of water, protein, minerals, and fat. These categories make up everything in your body from your organs, muscle, skeletal structure, body fat, to retained water. To understand measuring your body composition, you need to understand the two components that make up body composition, Fat Mass (FM) and Fat-Free Mass (FFM).

Fat Mass (FM)

Fat mass can be broken down further into essential and non-essential (storage) fat. The essential fat are necessary to maintain healthy bodily functions, lower your essential fats below optimum levels (2-3% Males, 5-12% Females) can be very detrimental your health. Essential fat makes up much of your bone marrow as well as body cell membranes. Non-essential or storage fat, is subcutaneous or stored between your skin and muscle or forms a protective coat for your organs call visceral fat. This fat helps visibly makeup your body. Basically fats that are extractable lipids are known as Fat Mass (FM).

Fat-Free Mass (FFM)

Fat-free mass (FFM) is everything else that makes up your body outside of fat mass (FM). This includes all water that is retained, muscles, bone structure, connective tissue, and organs. FFM can be affected and fluctuate based on the following:

Bone density

Body water




Testing Your Body Composition

As discussed before, utilizing the weight on a typical scale, does not tell the full story. Also, utilizing Body Mass Index (BMI) is outdated and is very mislead as it only takes into account your weight in relation to your height and age, and does not account for muscle mass, bone mass, water weight, etc. There are a few common types of methods to measure body composition that vary in their level of accuracy. A few of the these methods include:

Body caliper/Skinfold method

Bioelectrical impedance analysis (BIA)

Hydrostatic weighing

Most of them output results in the form of:

Fat Mass (FM)

Body fat percentage, body weight fat, visceral fat, etc.

Fat-Free Mass (FFM)

Lean muscle mass

Skeletal muscle mass

Body water weight (contains most of the weight for organs)

Bone density/mass

Body caliper/Skinfold method

This method is the least expensive of the three and is done through the sole use of a body caliper. Most local gyms offer this service in addition to their personal training programs or you can simply buy a caliper and test yourself. For accuracy, measurements should be taken from the same site each time measurements are recorded and on the same side of the body. To take measurements, the target site skinfold is placed into the caliper and recorded. Some common recording sites in men are the chest, abdomen, and thigh. For women, common sites include the triceps, thigh, and hip region. Measurements are then plugged into an equation to give you your body fat percentage. What ever percentage is left is what your Fat-free mass (FFM) is comprised of.


Bioelectrical impedance analysis (BIA)

This method is based on the human body’s capability to produce electrical conduction due to the intracellular and extracellular fluids. The key is that since the body (FFM) is most made up of water and electrolytes, it conducts an electrical current that returns an index of total body water, which gives an estimate of Fat-Free Mass. To test, while lying on a table, electrodes are placed on your hands and feet that pass the electrical currents through your body. Although this is a very accurate way to test your body composition, it can be pricey to obtain the equipment.

Hydrostatic weighing

This method is the most accurate form of testing and is offered at many medical and sports medicine facilities. The equipment is by far too expensive for personal ownership, however, going to a facility that offers this sort of testing can be relatively inexpensive. The Archimedes’ Principle is the defining factor of this form of testing in stating that an object submerged in fluid loses weight equivalent to the weight of fluid displaced by the object volume. This principle focuses on body density, meaning that leaner individuals will have higher density submerged in water due to muscle or bone have a higher density than fat. The equipment looks like a small swimming pool that is hooked up to a computer/analyzer. When measuring, the following help determine body density:

Residual lung volume (amount of air remaining in lung pockets after a complete exhale)

Body weight

Underwater weight

Hydrostatic testing takes into account the previously mentioned Fat Mass (FM) and Fat-Free Mass (FFM).


All three of these methods can be a great baseline when tracking your progress. Once you start with one method, continue to use the same method and you will be amazed at how your body can change week-to-week. Another more convenient method is a personal at-home body composition scale. These are relatively inexpensive and work similarly to the BIA test, however, only sending electric impulses through your feet. These types of scales can give you a baseline to where you are at with body fat percentage, bone mass, muscle mass, and water weight. A drawback to these scales is that they are not as accurate as the before mentioned methods. However, if you test routinely under the same circumstances (fasted, morning-time for ex.), you can track how each measurement changes from each testing, helping you determine that progress is being made.

Once you start measuring your success by body composition, you will be on your way to crushing your goals and pushing your body behind what you knew was possible.

Below is a Body Fat Percentage table (men/women) based on the general population.

*This is not absolute and should only be used as a guideline. Consult your physician for certainty on where your ideal body fat percentage should be.


Women   Men
<15% Risky (low body fat) <5%
15-18% Very lean 5-8%
19-22% Lean 9-12%
23-30% Moderate 13-20%
31-40% Excess fat 21-30%
>40% Risky (high body fat) >30%



University of Utah, College of Health

“Body Composition Information”

URL: http://www.health.utah.edu/peak/services/health_fitness_testing/body_composition_information.html

University of New Mexico

“Getting a Grip on Body Composition”

URL: http://www.unm.edu/~lkravitz/Article%20folder/underbodycomp.html

NCBI, US National Library of Medicine, National Institutes of Health

“Measuring Body Composition”

Published July 2006; URL: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2082845/

University of Texas-Arlington

“Body Composition”

URL: http://www.uta.edu/faculty/beckham/Body%20Composition.pdf


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