Body composition and analysis

By
Dr. Vidhi Thakar(PT)
Assistant Professor
ARIP
Charusat
Changa


Body Composition and analysis provides information (like
% of body fat, fat distribution, body segment girth etc.)which
are pertinent to athletic performance and for reducing risk
factors associated with musculoskeletal injury and disease.
Learning Objective
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Mc Ardle & Katch- Essentials of exercise physiology,
ACSM's- Resource manual for guidelines for exercise testing and prescription
2


 Definition
 Body composition model
 Techniques of Body composition analysis
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Index


 Body composition describes the relative proportions
of fat, bone and muscles mass in the human body.
 It can be described at 5 levels: -
• Atomic- C, H, O, N
• Molecular – Protein, carbohydrates, lipids.
• Cellular – Fat cells, body fluids, Extracellular solids
• Tissue – Skeletal muscles, bone, blood.
• Whole body – body mass, stature, size, volume, density.
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Definition

 Total body fat = Essential Fat + Storage fat
 Essential fat – in bone marrow, nervous tissue, organs(Young
men – 12% of body mass, Young female – 15% of body mass)
 Storage fat – accumulates in adipose tissue(Young Men- 3% of
body mass, Young female – 12% of body mass)
 Fat free mass(FFM) = body mass – fat mass
 Lean body mass(LBM) contains non-sex specific essential
fat(4% - 7% of body mass)
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Fat

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Body Composition Model


 Categorized as direct, indirect or doubly indirect
methods
 Direct method(chemical analysis of whole body or
cadaver) is not suitable in the living body.
 Indirect method(hydrostatic weighing etc.)
- Component and property based model
 Doubly indirect method(skinfolds etc.)
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Body Composition Model


Body composition
analysis method
Indirect Methods
 Height, Body mass, BMI
 Waist and hip circumference
 Hydrodensitometry
 Skinfold assessment
 NIR
 ADP
 CT, PET
 MRI and spectroscopy
 US
 Isotopic dilution
 DEXA
 Three dimensional scanning
Factors to be considered
 Need of the individual
 Purpose of evaluation
 Cost of measurement
 Equipment needed
 Availability of the
assessment tools
 Training
 Advantages vs.
disadvantages
 Accuracy, reliability and
validity
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
 Stadiometer
 Subject removes shoes
 Stands straight up and heels together
 Takes a deep breath and hold it
 Stands with head level and looks straight
 Consider standard time and monitoring pre activity
level
• Measured in cms and inches
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Height


 Best measured on a calibrated scale with a beam and
movable weights
 Removes excess layer of clothing and shoes
 Empty pockets, remove jewelery and mobiles
 Consider a standard time
 Body weight(pounds) and mass(kilograms) are
different terminologies
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Body Mass


 Body mass/ height squared
 Determines risks of CVD, diabetes type II and
hypertension
 Poor predictor of body fat
 Not useful for resistance-trained population
 Study of overweight and obesity of larger population
it can be used
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BMI


Classification BMI(kg/m2)
Principal cut-off points Additional cut-off points
Underweight <18.50 <18.50
Severe thinness <16.00 <16.00
Moderate thinness 16.00 - 16.99 16.00 - 16.99
Mild thinness 17.00 - 18.49 17.00 - 18.49
Normal range 18.50 - 24.99
18.50 - 22.99
23.00 - 24.99
Overweight ≥25.00 ≥25.00
Pre-obese 25.00 - 29.99
25.00 - 27.49
27.50 - 29.99
Obese ≥30.00 ≥30.00
Obese class I 30.00 - 34.99
30.00 - 32.49
32.50 - 34.99
Obese class II 35.00 - 39.99
35.00 - 37.49
37.50 - 39.99
Obese class III ≥40.00 ≥40.00
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
 Involves measuring the density of the athlete’s body.
Dbody = Mbody / Vbody
 Volume of body can be determined by hydrostatic
weighing.
 Archimedes principle Archimedes principle - an
object (or human) immersed in fluid, loses an
amount of weight equivalent to the weight of the
fluid that is displaced
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Hydro-Densitometry(Underwater
weighing or hydrostatic weighing)


 Volume = Mass – underwater mass
 Volume corrected for water density :
Intestinal gas and RV
 Density body = Mass/Volume corrected
 Relative fat = 495/ Density body - 450
 Fat mass = (mass × relative fat)/100
 Fat free mass = mass – fat mass
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
 Variables needs to known to Use Hydro-
densitometry
Residual volume
Density of water
Amount of gas trapped in the gastrointestinal system
Dry body weight
Body weight fully submerged in water


Bioelectrical Impedance
 BIA is a rapid, non invasive and relatively inexpensive
method for evaluating body composition field settings.
 With this method, a low level electrical current is passed
through client’s body and impedance is measured with a
BIA analyzer
 TBW can be estimated from impedance because
electrolytes in TBW are excellent conductors of electrical
current
 When volume of TBW is large, the current flows more
easily through body with less resistance


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
 The resistance to current flow is greater in
individuals with large amounts of body fat, since
adipose tissue , with its relatively low water content
is a poor conductor of electrical current
 Because water content of fat free mass is large, FFM
can be predicted from TBW estimates
 Individuals with large FFM and TBW have less
resistance to current flowing through their bodies
than those with a smaller FFM
 Based on gender, age, ethnicity, physical activity
level and level of body fatness
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
 < 20 % BF (for American Indian male 17-62 yrs)
 FFM(Kg) = 0.00066360(ht2) – 0.02117(R) + 0.62854
(BM) – 0.12380 (age) + 9.33285
 ≥ 20 % BF (for American Indian male 17-62 yrs)
 FFM(Kg) = 0.00066360(ht2) – 0.02117(R) + 0.62854
(BM) – 0.12380 (age) + 9.33285
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
 < 30 % BF (for American Indian female 17-62 yrs)
 FFM(Kg) = 0.000646(ht2) – 0.014(R) + 0.421 (BM) –
10.4
 ≥ 30 % BF (for American Indian female 17-62 yrs)
 FFM(Kg) = 0.00091186(ht2) – 0.01466(R) +
0.29990(BM) – 0.07012 (age) + 9.37938
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 A densitometry method used in laboratory and
clinical settings to measure Body volume and
estimate body density
 Compared to hydrostatic weighing, it is expensive
requiring use of a whole body plethysmograph
 Plethysmograph is a large, egg shaped fiberglass
chamber that uses air displacement and pressure
volume relationships to derive BV(Boyle’s law)
 ADP is performed using the BOD POD system
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Air displacement
Plethysmography


 BV = Volume of air in empty chamber – Volume of
air remaining in the chamber after the client enters
chamber
 Equipment is expensive and is generally accessible
only in research facilities
 No physical performance requirements for clients
 Require special clothing
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Skin fold Thickness
measurements
 measures double
thickness of skin and
subcutaneous fat


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Assumptions
 predicts non-
subcutaneous fat
>50% of fat is
subcutaneous
 sites selected represent
average thickness of all
subcutaneous fat
 compressibility of fat
similar between
subjects
 thickness of skin
negligible
Limitations
 Technician error
 Skin fold thickness
affected by factors other
than amount of fat
- exercise increases skin
thickness
- dehydration reduces skin
thickness
- edema increases skin
thickness
- dermatitis increases skin
thickness
 Poorly predicts visceral
fat


 Skin fold caliper works on principle same as that of
micrometer to measure 2 points
 The pincer jaws exert a constant tension of 10
g.m/m2 at the point of contact with the double
layer of skin plus subcutaneous tissue
 The caliper dial indicates skin fold thickness in
millimeters
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
 Measuring skin fold thickness requires grasping a
fold of skin and subcutaneous fat firmly with the
thumb and forefingers pulling it away from
underlying muscle tissue following skin fold's
natural contour
 The skin fold is recorded within 2 seconds after
applying the full force of caliper
 This time limitation avoids skin fold compression
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
 Take great care in locating anatomical landmarks for
each site prior to measurement
 Do not take measurements immediately after
exercise, shift in body fluid to the skin spuriously
increases reading
 Take measurements on dry, lotion free skin
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
Recording
 Once applied to the skin fold site, the caliper
continues to displace subcutaneous interstitial
water, connective tissue and fat throughout the
measurement period until the skin fold’s rebound
force counteracts the caliper pressure
 More than 70 % of the total compression of skin and
underlying fat takes place within first 4 seconds after
applying caliper
 Thus to record uncompressed skin plus fat
measurement , the reading should be made within 1
or 2 seconds.
 Any prolonged delay in reading the caliper
underestimates the actual skin fold value
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
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
 Equations and constants for young and older men and
women predict an individual’s percentage of body fat
within ± 2.5 % to ± 4.0 % body fat units of actual value
 These equations should not be used to predict fatness in
individuals who appear excessively thin or fat or who
participate regularly in strenuous sports or resistance
training that can increase girth without altering
subcutaneous fat
 Girths also can analyze patterns of body fat distribution ,
including changes in fat distribution during weight loss
and gain
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Girth measurements


Common sites:-
A. Right upper arm : palm up, arm straight, and
extended in front of body, taken at the midpoint
between shoulder and elbow
B. Right forearm : Maximum girth with arm extended
in front of body with palm up
C. Abdomen : 1 inch above the umbilicus
D. Hips (buttocks) : maximum protrusion with heels
together
E. Right thigh : upper thigh just below the buttocks
F. Right calf : widest girth midway between ankle and
knee
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
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Predicting body fat from
girths
 Percentage of fat =
Constant A + Constant B
– Constant C – 10.2
 Fat mass = body mass ×
( % fat / 100)
 FFM = BM - FM
Advantages
 Easy to learn
 Quick to complete
 Inexpensive
 Waist circumference
can be used as an
indicator of disease risk


 WHR indicates relative fat distribution in adults and
risk of disease
 A higher ratio reflects a greater proportion of
abdominal fat with greater risk of Type 2 diabetes,
hypercholesterolemia, hypertension, and
atherosclerosis
 WHR = smallest abdominal girth (cm or in)/largest
hip girth (cm or in)
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Waist – To – Hip Girth
Ratio


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
 Based on the premise that the degree of infrared light
absorption is related to the composition of the
substance through which light passes
 Fat and Fat-Free Mass absorb and reflect light
differently
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Near Infrared Interactance
(NIR)


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Advantages
 Non-invasive
 Safe
 Easy to administer
 Field technique
Disadvantages
 It does not predict body
fat across a broad range
of body fat levels
 It provides less accuracy
than skin folds
 It overestimates body fat
in lean men and women
and underestimates it in
fatter subjects


Ultrasound technology can
1. Assess the thickness of different tissues(fat & muscle)
2. Obtain an image of the deeper tissues such as a muscle’ s
cross-sectional area
 The method converts electrical energy through a probe
into high frequency sound waves that penetrate the skin
surface in to underlying tissues
 The sound waves pass through adipose tissue and
penetrate the muscle layer and then reflect from the fat –
muscle interface to produce an echo, which returns to a
receiver within the probe
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Ultrasound


 It has application for determining total and
segmental subcutaneous adipose tissue volume
 US exhibits high reliability for repeat measurements
at multiple sites in lying and standing positions o the
same and different days
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
 Generates detailed cross-sectional, 2 dimensional
radiographic images.
 Passes x-ray beam through tissues of different
densities.
 Provides quantitative information on:
 Total tissue area
 Total fat and muscle area
 Thickness and volume of tissues w/i organ
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Computed Tomography


 Nuclear imaging technique which determine brown
fat content(it has imp. role in thermogenesis)
 Provides greater precision at organ and tissue level
than other scanning.
 Metabolic tracer are injected in body which are than
detected
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Positron emission
tomography(PET)


 Electromagnetic radiation, not ionizing radiation, in
strong magnetic field excites hydrogen nuclei of
body’s water and lipid molecules. Nuclei then
project detectable signal to visually represent various
body tissues.
 Provides quantitative information on total and
subcutaneous adipose tissue
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Magnetic Resonance
Imaging


 Measures total body weight(TBW) and estimates of
FFM and % body fat.
 TBW is calculated from compartment volume.
 Compartment volume is the ratio of the dose of a
tracer to its concentration in the bodily compartment
after equilibrium is achieved in the body.
 Tracer used areD2O, 18O and titrated water
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Isotopic dilution


Limitation
 Requires correction factor to account for errors in the
calculation of isotopic dilution space
 Isotopic dilution is costly
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
 Principal of absorptiometry is based on exponential
attenuation of X-rays at two energies as they pass
through the body.
 Based on 3 C model of total bone mineral stores,
FFM and fat mass
 X-ray are generated at two energies by X-ray tube
 A detector is positioned overhead on the scanning
arm and interface with computer is a needed for
scanning an image.
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Dual Energy X-ray
Absorptiometry


Limitation and benefits
 Individual size(tall person, obese person).
 Large and expensive instrument
 Assumes same amount of fat lies over bone and
neighboring bone free tissue
 Also assumes constant hydration state.
 Has more clinical utility than just % of body fat.
 Can provide regional measurement on the body
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
 Assess body shape and size via scanners that are
based on laser scanning, structured light or stereo
vision systems
 Subject stands motionless in the center of the scanner
wearing tight clothing and head cap.
 % of body fat determine by measuring body volume
and density with the help of multiple scan.
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Three dimensional body
scanning


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Body composition and analysis

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