What is body composition?

Question
What is body composition definition and what practical sense does it have? How one measures it?

Answer
Dear B.,

Body composition is what you consist of. This is, of course, a simplified definition. A comprehensive definition would list lean body mass (total weight minus fat,) and total weight would list muscle mass, internal organs' mass, e.g. blood, bones, etc. Body fat weight or more importantly, body fat percentage, is what interests dieters most unless they are bodybuilding buffs, in which case they struggle to increase muscle mass and fefinition.

Now, why body fat % is most important?  The assumption is simple: one with a wide frame will probably have more muscles. Because of that some healthy weight charts offer three weight ranges depending on whether your frame is narrow, average, or wide. Even this simple addition puts healthy weight in a broader scale: with the same height, one can have his or her healthy weight differ by up to 20 pounds, depending on body frame!

However, even with the same frame type the actual muscle mass can still be very different depending on muscle use and nutritional status. For example, a wide-framed sedentary person who puts on 20 pounds of pure fat will differ from the same frame body builder who puts on 20 pounds of muscle mass. So the only way to tell the real fatness is to measure the actual fat content in the body.

There are several ways of doing this. But first let us see what our bodies' major constituents are. Of these, two principal body components are: dry matter and water. You might want to consider lean and fat matter as well, but these two are closely related because muscles contain a lot of water while fat has much less. This is the basis of measuring body fat percentage using so called electrical impedance method (or bioelectrical impedance analysis (BIA). The more water -- the easier for very low electrical current to pass through the body.

However, this machine can be easily confused by such a common difference in people bodies' composition as hydration status that does not relate to the fat content. Depending on how much water is being retained, one's body weight might vary throughout a day as much as 4.5 to 5 pounds. Consequently, that varies the electrical resistance to the current of a fat measuring machine. This is why you are told not to drink coffee the day of the test, abstain of food intake for at least 4 hours before your fat test, and to lie down for at least several minutes. All the machine of this type have inbuilt software that adjusts the only parameter measured depending on many other parameters that are just being asked: age, gender, ethnicity, physical activity level. etc. I toyed around with this software myself and was amused having my fat percentage magically decreased as a result of cheating with my athletic level.

Another method, a good old one, is a so called skinfold measurement. You purchase a skinfold caliper (it's usually very inexpensive) and pinch your skin along with under-skin fat in several (7 to 20) designated areas, then produce a simple calculation as your caliper manual instructs. Why so many pinches? Because one can store his or her fat in quite different places: as you surely noticed, there are people having a tine waistline and broad hips, or that are heavy in the bottom and slim in the shoulders, and so on. By the way, the very fat distribution can tell about this particular person's health risks (you've heard of course of "apples and pears"), but this is another story.

There is also a test named Hydrostatic of Underwater weighing. It is based on the fact that fat and muscle have different physical density with the same volume of fat being much lighter than that of muscle. Immersing the body into the water (head is being left above the surface, but then it usually doesn't have too much of fat), it is possible quite accurately measure the overage body density and thus body fat content. The disadvantage is that the lung volume can contribute rather significantly to the total body volume, and the lungs inflate if a person is under a considerable stress. Imagine what happens if the person being tested is a hydrophobic or is hyperventilating: he or she will respirate excessively, with all the gasped air measured as the fat volume.

One of the newest method on the market is probably the Near-Infrared Light Technology. It is based on the physical law that fat and protein (muscle constituent) absorb light in unique for the each of them portions of light spectrum. In some precise light wave frequencies, the light rays being directed through your body will be absorbed by fat matter while reflected by the lean body matter. The method is considered promising yet not free of faults. For instance, the measurements are being done in only one place of the body - dominant biceps. However, the proponents argue that this is the most representative point and correlates with the total body fat better than any other body places.

This is in theory. Practically, you can use a very simple circumference method with  no tools other than measuring tape and online calculator. You can find it here:

http://www.bestofweightloss.com/body_fat_calculator.html

Now that you've got your body fat measured, what does it tell you?

# A healthy male's body should be approximately 12 percent to 18 percent fat.
# In females the number is slightly higher; approximately 14 percent to 20 percent fat.

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