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09 What's the best way to measure body fat percentage?




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This article is from the Diet FAQ, by Claudia McCreary cookignnewsletter@chef.net with numerous contributions by others.

09 What's the best way to measure body fat percentage?

Several methods are in use, and unfortunately the same person is likely to
get different readings from different methods. As with weighing yourself,
your best bet is to pick one method, stick with it, and watch trends rather
than specific numbers.

* Immersion: This method is based on the fact that lean tissue (muscles,
bones, etc.) tends to sink in water, while fat floats. The client is seated
in a chair which hangs from a scale, rather like a scale in a supermarket's
produce section. The chair and the client are lowered into a pool of water
until the client is completely immersed, and the client's weight (while
immersed) is recorded. The fatter you are, the more you tend to float, and
the lower your immersed weight will be--muscular people weigh more than fat
people while immersed. The immersion method is highly accurate, but
obviously requires a lot of equipment. Covert Bailey advises that you can
estimate your fat ratio by seeing how well you can float on your back in a
regular swimming pool: above 25% fat, people float easily; people with
22-23% fat (a healthy level for women) can usually float while breathing
shallowly; at 15% fat (low for a woman, healthy for a man), one will usually
sink slowly even with a full chest of air; at 13% or less fat, one will sink
readily even with a full chest of air, even in salty ocean water.

* Calipers: The physician or technician making the measurement gently
pinches up folds of tissue in areas that normally accumulate fat readily
(such as the back of your arm, your stomach just above the waistline, and
your hip area), then uses calipers to measure the width of these folds. The
thicker the folds are, the higher the fat ratio in your body. This method is
only somewhat accurate since it measures just the fat which accumulates in
these regions, not that which is imbedded between muscle fibers. However, it
is a simple and inexpensive procedure. Electrical impedance: This method
is based on the fact that fat and lean tissues have different levels of
electrical conductivity (muscle tissue conducts electricity better than fat
tissue does). The test is simple, completely painless, and takes just a few
minutes; a couple of sensors are attached to the body (e.g., to a hand and a
foot) and used to measure the body's resistance to a weak electrical
current.

* Infrared measurement: This method is based on the fact that an infrared
beam travels faster through muscle than fat. An IR beam is bounced off a
bone (e.g., in the upper arm) and the time that it takes for the signal to
return is measured. As with electrical impedance, the procedure is simple
and completely painless.

 

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