Body composition and its Assessments.

1. BODY COMPOSITION

2. WHAT IS BODY COMPOSITION
 Body composition is used to describe the percentages of fat,
bone, water and muscle in human body.
 Body composition is a method of describing what the body is made of.
 Body composition analysis can accurately show changes in fat mass,
muscle mass, and body fat percentage.
 It also influence health outcomes, and its measurement is increasingly
valuable in clinical practice. 2

3. DIVISION OF TERMINOLOGY
Overweight
Over fatness
Obesity
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4. BODY MASS INDEX (BMI)
 Body mass index (BMI), derived from body mass and stature, to
assess “normalcy” for body weight
BMI = Body mass (kg) / stature (m 2 )
 It has curvilinear relationship with the all-cause mortality ratio.
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5. BMI LIMITATIONS
 The BMI tables, fails to consider the body’s proportional
composition or the all important component of body fat
distribution, referred to as fat patterning.
 In addition, factors other than excess body fat—bone, muscle
mass, and even increased plasma volume induced by
exercise training—affect the numerator of the BMI equation.
 A high BMI could lead to an incorrect interpretation of
overfatness in lean individuals with excessive muscle mass
because of genetic makeup or exercise training.
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6. MODELS OF BODY COMPOSITION
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7. REFERENCE MAN AND WOMAN
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8.  Fat-Free Body Mass : Represents the body mass devoid of all extractable
fat (FFM= Body mass- fat mass)
 Example : Body mass = 75.1 kg ; Body fat = 23.6%
Fat mass = Body mass * % body fat
FFM = Body mass - fat mass
 Lean Body Mass : It consists of the small percentage of non-sex-specific
essential fat equivalent to approximately 3% of body mass.
 Reference woman- Whole body density of 1.040g/cm3 represents a body fat
percentage of 27% , in which approximately 12% is the essential body fat.
 Reference man- Whole body density of 1.070g/cm3 represents a body fat
percentage of 15%,in which approximately 3% is the essential body fat. 8

9.  Total body fat = Essential Fat + Storage fat
 Essential fat – fat in heart, lungs, liver, spleen, kidneys,
intestines, muscles, and lipid-rich tissues of the central
nervous system and bone marrow. Normal physiologic
functioning requires this fat.
 Storage fat – accumulates in adipose tissue
 A similar proportional distribution of storage fat exists in men
and women (12% of body mass in men, 15% in women), but
the total percentage of essential fat in women that includes
the sex-specific fat averages four times the value in men.
 The additional essential fat most likely serves biologically
important functions for child bearing and other hormone-
related functions.
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10. MINIMAL LEANNESS STANDARD
 Lower limit exists
 In men, the lower body fat limit is calculated as,
Storage fat – Body mass
 As in the reference man, the lean body mass (61.7kgs) consists
2.1kgs(3%) of essential body fat. Encroachment into this reserve
may impair optimal health and capacity for vigorous exercise.
 Same as in reference woman, the lower limit includes approximately
12% essential fat.
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11. TECHNIQUES TO ASSESS BODY
COMPOSITION
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DEXA
Air displacement plythesmography
Hydrostatic underweighing
Skin fold thickness
SIRI EQUATION:
% body fat = (495 / body
density) – 450
BIA

13. HYDROSTATIC WEIGHING
 It is also referred to as "underwater weighing", "hydrostatic
body composition analysis", and "hydrodensitometry" is a
technique for measuring the density of a living person's body.
 The procedure is based on Archimedes principle, which states
that: The buoyant force which water exerts on an immersed
object is equal to the weight of water that the object displaces.
 Once body density has been calculated from the data
obtained by hydrostatic/underwater weighing, body
composition can be estimated.
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15. HOW TO CALCULATE
Volume = weight
– underwater
weight
Density (body) =
Weight(b) /
Volume (b)
Relative fat =
495/density - 450
Fat mass =
(weight x relative
fat) / 100
FFM = weight –
fat mass
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16. EXAMPLE
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 Residual volume
 Density of water
 Amount of gas trapped in
the gastrointestinal system
 Dry body weight
 Body weight fully
submerged in water
 Time consuming
 Not feasible to test large
number of people
 Requires measurement of
residual lung volume (if
unknown, can be estimated)
 Difficult to perform on the
aquaphobic
Variables that need to be
considered
Drawbacks

18. DUAL-ENERGY X-RAY ABSORPTIOMETRY
 The DEXA method measures body fat, muscle and total
body bone mineral (TBBM) using two X-ray energies.
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19. AIR DISPLACEMENT METHOD
 Method was adapted by Helium displacement plethysmography.
 Computerized pressure sensors determine the amount of air displaced
by the person
 Body volume is calculated by subtracting the air volume with the
person inside the chamber from the volume of the empty chamber (air
in the lungs is taken into consideration)
 Body density and percent body fat are then calculated
 BOD –POD device used
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20. Body volume =
initial volume –
reduced chamber
volume with the
subject inside
Body density =
body mass
(measured in air) /
body volume
(measured in
BOD POD)
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21. SKINFOLD MEASUREMENT
 The rationale for using
skinfolds to estimate body fat
comes from the
interrelationships between-
adipose tissue directly
beneath the skin, internal fat
and whole body density.
 Anatomic sites- Triceps,
Subscapular, Suprailiac,
Abdominal and Upper thigh
sites.
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22. GIRTH MEASUREMENT
 Along with prediction
of body fat, it analyzes
patterns of body fat
distribution.
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23. HOW TO CALCULATE
Measure girth of
upper arm,
abdomen and
right forearm
Determine
constants from
chart
Percentage fat =
A+B – C – 10.2
Fat mass = body
wt x (% fat / 100)
FFM = body wt.
– fat mass 23

24. CONSTANTS CHART
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25. BIOELECTRICAL IMPEDANCE ANALYSIS (BIA)
 A small alternating current flowing between two electrodes
passes more rapidly through hydrated fat-free body tissues and
extracellular water than through fat or bone tissues because of
the greater electrolyte content (lower electrical resistance) of
the fat-free component.
 The body’s water content conducts the flow of electrical
charges, so when current flows through the fluid, sensitive
instrumentation can detect the waters’ impedance
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26. Factors that affect the
accuracy:
1) Hypohydration
2) Hyperhydration
3) Skin temperature
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27. ULTRASOUND ASSESSMENT
 The method converts electrical energy through a probe into
high-frequency (pulsed) sound waves that penetrate the skin
surface into the underlying tissues.
 The sound waves pass through adipose tissue to penetrate
the muscle layer.
 They then reflect from the fat–muscle interface (after reflection
from a bony surface) to produce an echo, which returns to a
receiver within the probe.
 The time required for sound wave transmission through the
tissues and back to the transducer converts to a distance
score that indicates fat or muscle thickness
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28. MAGNETIC RESONANCE IMAGING (MRI)
 Magnetic resonance imaging provides tomographic images
with high soft tissue contrast, which enables quantification of
fat and muscle compartmental volumes.
 Especially Dixon methods, that produce co-registered water
and fat images, facilitate the separation of both adipose and
lean tissue compartments.
 Scanning the whole body with sufficient spatial resolution is
achievable in 6–8 minutes on modern scanner systems, using
specialized body composition protocols available today
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29. DETERMINING GOAL BODY WEIGHT
Fat mass =
body weight
x % body fat
FFM = body
wt. – fat
mass
Goal body
wt = FFM /
(1.00 –
desired %fat)
Goal fat loss
= Current
body wt. –
goal body wt.
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30. REFERENCE
 William D.Mcardle(2010), Exercise Physiology; Chapter-28, Body
composition assessment
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31. THANK YOU
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