Body Composition Measurements and Why They May Not Be That Important

By Dr. Marc Luko

With the start of a new year comes new fad diets, weight loss programs, and sparked interest in “finally using that exercise bike I bought two years ago.” As a strength and conditioning coach, I am all about individuals meeting their health and fitness goals. With that said, I find that there are some out there that may be looking at the wrong metrics when it comes to determining whether or not they are “fit”, or, losing fat.

The most common metric used in determining body composition is one that keeps many of us up at night—our bodyweight.  Why not use bodyweight to determine our fitness? It’s an easy number that we can use to compare to our friends, our high school days, and bikini models. Therein lies the problem. Our bodyweight is a combination of all of our tissues, organs and liquids, so, while the scale tells us what the composite number is, it does not tell us how that number came about. For example, if I hand you a box that weighs 100 pounds, but you cannot see what is in it, you will have no idea whether it is filled with junk food or vegetables. All that you know is that it weighs 100 pounds. That is the largest shortcoming in regards to using a bodyweight scale to determine fitness or fat loss. This is especially true considering muscle weighs more than fat, so, an increase in weight may be interpreted as “getting fat” when in reality, you could be losing it.

Another method for measuring body composition, which is seen a lot in the fitness industry is what is referred to as Bioelectrical Impedance Analysis (BIA). BIA is quick, easy, and in some cases can give a relatively accurate estimate of body fat percentage. The device measures body fat by sending a current (no, you will not get shocked using this device…unless you try this underwater, which is not advised for any electrical device, right?) throughout your upper body. The amount of time the signal takes to complete the “circuit” through your body allows the device to estimate body fat percentage. The concept is that muscle tissue is composed of more water, which is a conductor of electricity, therefore, the faster the current makes its way through the circuit, the more muscle tissue there is in an individual, in theory. With that said, you can see where this can be an issue in the case of dehydration. BIA devices can be purchased at local drug and fitness stores for relatively cheap, but, as with any device, it is not 100% accurate, so, take that as you will.

One method that used to be  more common of body composition measurement is one that has died down over the years—the skinfold caliper. This device is also very cheap but does require good technique. For this method, the caliper is used to “pinch” 3 different body sites (different for males and females) and measure the thickness of the skinfold. These numbers are then put into a formula that estimates body fat percentage. When used correctly, skinfold calipers have been shown to be as accurate as the gold standard, hydrostatic weighing (Kirkendall 1991).

The last method is the most accurate method and that is hydrostatic weighing. If this sounds to you like you are going to have to go under water, you would be correct. The method behind hydrostatic weighing is the concept of displacement (for those interested, look up “Archimedes’ principle”). An example of displacement is going into a bathtub. Before you enter the bathtub, the water is at a certain level, or, volume. Once you enter the bathtub, that water level will rise. That change in water level is an example of displacement which can be used, in combination with body mass, to determine body composition. Now, this cannot be determined in a bathtub like the example just given, but is determined in a big “pool” where an individual is submerged underwater. You can guess that this comes with its limitations, particularly with those not keen on being underwater. This method is also fairly expensive, so it is mostly used in professional sports.

In closing, what is the BEST method to determine body composition? The answer is that there isn’t one. Since most of us are not professional athletes, trying to find every number, device and method to figure out body will only drive you crazy and deter you from your fitness goals. Numbers that you cannot deny are those in your training program. If you can squat 100 pounds for one repetition one day and then you do it 6 weeks later for 10 repetitions, guess what, you’re more fit than you were 6 weeks ago! Consistency is key in any program whether it be for fat loss, strength gain, or a combination of the two, as they are never truly mutually exclusive.  A healthy, consistent diet and an individualized strength and conditioning  program, , will help anyone achieve their fitness goals without ever having to be dunked in water, pinched by a caliper or discouraged by a scale. If you focus on that, you won’t need to figure if your exact body composition has improved, because you will feel it.

For more information on proper dieting and healthy foods, please, see our Specialist in Fitness Nutrition, Jenn! For strength and conditioning, feel free to contact any of our trainers at Atlas!


Kirkendall, D. T., Grogan, J. W., & Bowers, R. G. (1991). Field comparison of body composition techniques: Hydrostatic weighing, skinfold thickness, and bioelectric impedance. The Journal of Orthopaedic and Sports Physical Therapy, 13(5), 235-239. doi:1691 [pii]


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