If you’re serious about improving your health and fitness, chances are you’ve focused on building muscle or losing fat at some point. While the scale can show you if you’re gaining or losing weight, it can also leave you guessing what exactly spurred this change. Was it your diet that caused you to lose fat, or are you losing precious muscle that you worked hard to build? Is your mass-building effort causing too much fat gain while you’re attempting to bulk up? The best way to truly know what is behind the changes in your body weight is by tracking your body composition, and there are several useful methods that we’re going to discuss in this article.
Historically, the first widely accepted methods of measuring body composition included surface anthropometry (skinfold caliper testing) and hydrostatic weighing (dunk-tank); however, these methods are susceptible to human error, require intrusive test procedures, and have limited accuracy. Over the past three decades, technological advancements have led to new methods that provide safe, non-invasive, accurate body composition measurements. These new methods include Differential X-Ray absorptiometry (DXA or DEXA); Air Displacement plethysmography or ADP (e.g., BOD POD); three-dimensional photo scanning (e.g., Fit3D, Styku); and Bioelectrical impedance measurement (e.g., Tanita, InBody, Seca).
If you’re going to spend time and money tracking your composition, it’s worth understanding the pros and cons of the different methods and select the one that is best for you.
In the first part of this series, we’re going to look at body composition models and the true gold standard in composition measurement. In future posts, we will look at how each measurement technology works, the type of accuracy you can expect, and the influence of test procedures on repeatability.
Body Composition Models:
Body composition models classify body matter into distinct groups. The most basic model divides the body into Fat Mass (FM) and Fat-Free Mass (FFM):
In the two compartment model, everything that is not fat gets classified as FFM. This includes muscle, bone, organs and fluid mass.
To overcome some of the limitations of the two-compartment models, three-component models take into account the hydration state of the individual. Deuterium Dilution is an accurate method to measure total body water, allowing FFM to be divided into Water and Dry Mass.
In our next post, we will look at some of the more common methods of body composition testing to help you understand your test options and make the choice that is best for you.
Brozek, J., Grande, F., Anderson, J.T., and Keys, A. 1963. Densitometric Analysis of Body Composition: Revision of some quantitative assumptions. Annals of the New York Academy of Sciences 110:113-140
Siri, W.E. 1993 Body Composition from fluid spaces and density. Analysis of methods, 1961 Nutrition 9(5): 480-491
Withers, R.T., Lafogia, J., Heymsfield, S.B., 1999. Critical appraisal of the estimation of body composition via two-, three-, and four-compartment models. American Journal of Human Biology 11(2):175-185