Transcript Body Composition

 Definition: describes the percentages of fat, bone,
muscle, and fluid that make up body weight.
 Because muscular tissue takes up less space in
our body than fat tissue, our body composition, as
well as our weight, determines leanness.
 Factors that affect a person’s body composition
may include: heredity, diet, exercise, occupation.
Two people at the same height and
same body weight may look
completely different from each other
because they have a different body
composition.
Male and Female
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The National Institute of Health recommends that a healthy adult male's body should
have between 13 and 17 percent fat.
A healthy female's body should be composed of between 20 and 25 percent fat.
FITNESSGRAM suggest that there is an optimal range within the HFZ. Ideally,
students should strive to be within the optimal range, which is 10% to 20% fat for
boys, and 15% to 25% fat for girls.
Why is the FitnessGram different than that of an adult? Answer: kids are still
growing.
Levels significantly above these amounts may indicate excess body fat.
Body composition (particularly body fat
percentage) can be measured in several ways.
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Skinfold measures
Bioelectrical Impedance
Underwater Weighing
Body Mass Index (BMI)
Description: This method is
the most widely used body
composition testing method for
assessing percent body fat.
Equipment used for this
assessment includes a skinfold
caliper. A Skinfold Caliper is
designed specifically for simple
accurate measurement of
subcutaneous tissue. Either a
7 or 3 site skinfold may be
assessed.
7 site skinfold:
chest
triceps
subscapular
axilla
suprailiac
abdomen
thigh
3 site skinfold (Men):
chest
abdomen
thigh
3 Site Skinfold (Women)
tricep
suprailiac
thigh
How accurate is it?
If each test is performed
correctly according to the
recommended guidelines,
there is a +/- 3% error
Advantages and Disadvantages
• Advantages:
• Easy to use once skill has
been mastered
• Does not require much time
• Noninvasive method
• Inexpensive way of estimating
percent body fat
• Disadvantages:
• Technical sources of error
• Mostly concerned with
subcutaneous fat (under the
skin)
• May not be an ideal
measurement for those who
are obese and very lean
Bioelectric Impedance
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Description: By standing barefoot on metal foot plates, an undetectably low
voltage electric current is sent up one leg and down the other. Since fat is a
very poor conductor of electricity, a lot of fat will impede the current more so
than a lot of lean tissue. By measuring the resistance to the current, the
machine estimates the percent body fat.
Advantages vs. Disadvantages
• Advantages:
• Requires little or no technical
knowledge of the operator or
the client
• Testing itself takes less than a
minute
• The unit can be easily
transported from place to place
• Requires only an electrical
outlet and the machine itself
• Disadvantages:
• This method has a higher
standard error range than most
people desire
• Tends to consistently
overestimate lean people and
underestimate obese people
Underwater Weighing
A.K.A. Hydrostatic Weighing
• Description: This method uses Archimedes principle which states
that when a body is submerged in water, there is a buoyant counter
force equal to the weight of the water which is displaced. Because
bone and muscle are more dense than water, a person with a larger
percentage of fat free mass will weigh more in the water and have a
lower percent body fat. Conversely, fat floats. Therefore, a large
amount of fat mass will make the body lighter in the water and have
a higher percent body fat.
How accurate is it?
If each test is performed correctly according to the recommended guidelines, there is a
+/- 1.5% error. (Note: Accuracy depends on the client’s ability to blow all the air out of
their lungs both during a pre-test screening with a spirometer, and during the test itself.
Since air makes the body float, inability to perform either of these maneuvers will result in
miscalculation of the percent body fat.)
• Advantages:
• This method is currently
considered the "gold standard"
in percent body fat
measurement
• Repeat measures usually
prove consistent, and can be
used to chart progress
• Disadvantages:
• This method usually requires a
lot of equipment and space
• Testing is time consuming and
involved
• Requires in-depth knowledge
to administer the tests and
compute the calculations
• Being submerged under water
may be difficult and produce
anxiety for some
• Provides an indication of the appropriateness of
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a child’s weight relative to height.
Body mass index is determined by the following
formula: weight (kg) / height squared (m)
Example: a student weighing 100lbs (45.36
kilograms) who is 5 feet (1.52 meters) tall would
have a BMI of 19.6. Another student of the
same weight but 5 feet 2 inches tall would have
a BMI of 18.3.
BMI
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Advantage
Fast
Does not require much skill
Procedure is less invasive than
skinfold testing and may be
better accepted in some
districts.
• Disadvantage
• Estimates based on height and
weight such as BMI result in
5% to 6% error because body
weight reflects muscle and
bone mass and not just fat
mass.
• Body mass index is not the
recommended procedure for
determining body composition
because it does not estimate
the percent of fat.
• It merely provides information
on the appropriateness of the
weight relative to the height.
Good Body Composition
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Decrease levels of body fat that cause obesity
Decrease risk of coronary heart disease
Decrease chances for stroke
Decrease chances for diabetes
Lower blood pressure
Lower Cholesterol levels
Lifetime
• Like other dimensions of health-related
fitness, body composition does affect
health status (even in childhood) and does
improve with regular participation in
physical activity and diet.