Body composition refers to the relative proportions of body
weight in terms of lean body mass and body fat. Lean body
mass represents the weight of muscle, bone, internal organs, and
connective tissue. Because muscular tissue takes up less space in
our body than fat tissue, our body composition, as well as our
weight, determines leanness. Two people of equal height and body
weight may look completely different from each other because they
have a different body composition. Body fat represents the
remaining fat tissue. Body fat serves three important
functions: (1) Act as an insulator to conserve heat; (2) Provides
metabolic fuel for the production of energy; (3) Acts as padding to
cushion your internal organs. It’s essential to maintain some
body fat, but an excess level may poses a serious health risk in
adults.
How is body composition measured?
Body composition (particularly body fat percentage) can be
measured in several ways. The most frequently used techniques
are:
- Bioelectrical Impedance
Analysis (BIA): The analysis that
you just received is BIA uses a scale to send an undetectably low
voltage electric current up one leg and down the other. Since fat
is a poor conductor of electricity, fat will impede the current
more so than lean muscle tissue. By measuring the resistance to the
current, the machine estimates the percent body fat. BIA represents
a 2-compartment model for estimating body composition, because it
can divide the body into two compartments: fat and all other
fat-free mass that does include bone. If the pre-test protocol is
followed the test has ± 3% accuracy. This form of measurement is
the most widely used due to yielding timely results within
seconds.
- Skinfold Testing: When performed by a trained
professional skinfold testing is more accurate than bioelectrical
impedance. Skinfold testing uses a tool called a caliper to pinch
multiples places on the body in order to measure the thickness of
the fold. Skinfold testing can include at the minimum three fold
sites and at the maximum nine sites including areas such as the
chest, subscapular region, arms, thighs, and abdominal areas. These
measurements are used to estimate total body fat with a margin of
error of approximately four percentage points depending on the
experience and accuracy of the tester and by the adherence of the
pre-test protocol followed by the participant.
- Dual- Dual-Energy X-Ray Absorptiometry
(DXA: DXA, once used for determining bone
density, evolved into a technique for also estimating body
composition. DXA represents a 3-compartment model for
estimating body composition, because it can divide the body into
three compartments: fat, bone mineral, and all other
fat-free mass that does not include bone. Thus, unlike
2-compartment models, DEXA is not subject to errors caused by
variations in bone density among different ethnicities.
- Whole-Body Air Displacement Plethysmography (Bod
Pod): The technique measures the volume of air displaced
by the person and the measurement involves air being gently blown
around the subject during two 1-minute periods. Body volume is
combined with body weight (mass) in order to determine body
density. The technique then estimates the percentage of body fat
and lean body mass through known equations (for the density of fat
and fat free mass).
- Other techniques are: Isotope dilution (hydrometry),
Magnetic resonance imaging (MRI, computed tomography (CT), and
multicompartment models.
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