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3 Ways
Of Measuring Bodyfat
1.
Underwater Weighing: Underwater weighing is the most
accurate method for determining your percent body fat, but
it's the least practical because it's done with
sophisticated equipment at university research facilities.
This method is based on the premise that fat floats - think
of how oil rises to the top in a bottle of salad dressing.
Therefore, by submerging a body in a tub of water, you can
determine how much of it is lean and how much is
not.
You sit in a large tank or tub full of water in
a special chair with a weight belt around your waist. A
trained technician then submerges you beneath the surface
of the water as you force all the air out of your lungs.
You must remain underwater for about 10 seconds so that
the technician can record your weight. The technician
repeats this procedure eight to ten times in order to
determine an average.
The technician measures your body's volume by
computing the difference between your body's weight
measured in air and its weight underwater. The technician
then calculates your body density by dividing your body
mass by the volume of the water that it displaces, minus
any air left in your lungs. After computing density, the
technician uses another formula to determine your percent
body fat.
2.
Skin fold thickness: Measuring skin-fold thickness (the
amount of fat just under the skin) is a simpler method for
determining percent body fat. When done by an experienced
person, it is a very accurate predictor of total body fat.
However, this method can yield inaccurate results if not
done by a skilled practitioner or if performed on an older
person or on someone who is severely overweight. Given that
the results can vary greatly depending on the practitioner,
you should view the results skeptically.
A person trained in skin-fold measuring, such as
a doctor, dietitian, or health club staffer, measures
your skin-fold thickness by using skin-fold calipers at
the upper arm, upper back, lower back, stomach, and upper
thigh. The technician takes two sets of measurements and
obtains an average at each site. Then he or she converts
the millimeters that the calipers measure and places
those numbers in a formula to arrive at the percent body
fat of your entire body.
3.
Bioelectrical impedance: Bioelectrical impedance is
another relatively simple method for determining percent
body fat, but it can produce inaccurate results if a person
is dehydrated, overhydrated, severely overweight, or older
with little muscle mass.
A trained technician takes readings from a
machine that delivers a harmless amount of electrical
current through your body to estimate total body water,
which reflects the amount of muscle or lean tissue you
have. (Muscle contains water, and fat contains very
little water.) The technician then determines the amount
of body fat you have between your body weight and your
lean tissue.
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