Body composition describes the relative proportions of fat, bone, and muscle mass in the human body. There are several methods to assess body composition, including direct methods like chemical analysis and physical dissection, as well as indirect methods like bioelectrical impedance analysis, hydrodensitometry, air displacement plethysmography, skin fold measurements, girth measurements, and dual-energy X-ray absorptiometry. Understanding body composition provides information on fat percentage, fat distribution, and lean body mass, which is important for athletic performance, injury risk assessment, and health monitoring.

1. BODY COMPOSITION
• Mihir Baria
• 1ST Year MPT

2. What is body composition?
• Body composition describes the relatives
proportions of fat, bone, muscle mass in the
human Body.
• Body composition = Body is relative amounts of
fat free mass and fat mass.
• It refers to the body’s chemical composition.
• There are 3 models of body composition::
1.chemical model
2. Anatomical model
3.Two compartmental model.

3. In Fat,
Two type of fat
1.Essential fat::(Male- 3 to 6% , female= 8 to 12% of body mass)
Essential fat consists of fat in the 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.
2.Storage fat::
accumulate in adipose tissue

4. Why we need Body composition analysis
• Body composition and analysis provides information about % of body
fat, fat distribution, body segments girth.
• How much fat lose versus how much muscle to gain?
• Which are participant to athletic performance and for reducing risk
factors associated with Musculoskeletal injury and disease.

5. Assessing Body Composition
• Five level Multi component model to assess and interpret body
composition::

6. Two method
• Direct method
• Indirect method
Direct method
• Chemical solution dissolves
• Physical dissection

7. Assessing body composition (indirect
method)
1. Height, weight, BMI
2. W- H ratio
3. Hydro densitometry
4. Air displacement method
5. Skin fold method
6. Girth measurement
7. Bioelectrical impedance analysis
8. Ultrasound
9. DEXA

8. Height,weight and BMI
• Height:: it is measured by Stadiometer
• Weight :: it is measured by Weighing scale.
• BMI:: measured by following equation
BMI= Weight / (Height)²
Weight in kg
Height in m

9. Waist Hip ratio
• The WHO STEPS protocol recommends that the subject stands with arms at the sides,
feet positioned close together, and weight evenly distributed across the feet.
• The measurement be made at the approximate midpoint between the lower margin of the
last palpable rib and the top of the iliac crest(waist circumference), waist circumference
should be measured at the end of a normal expiration, when the lungs are at their
functional residual capacity.
• The hip circumference measurement should be taken around the widest portion of the
buttocks(Hip circumference)
• Which calculates the ratio of your weight to your height, WHR measures the ratio of your
waist circumference to your hip circumference. It determines how much fat is stored on
your waist, hips, and buttocks.
• It’s indicate body fat distribution patterns.
• According to the World Health Organization (WHO), a healthy WHR is:
0.9 or less in men
0.85 or less for women

10. Hydrodensitometry
Densitometry::
Measuring the density of the body.
Density is defined as mass divided by volume:
D=M/V
M=mass of body( measured by scale weight)
V= volume of body(measured by
1. hydrostatic weighing
2.Volume also measured by air displacement techniques.
Densitometry has long been the technique of choice for assessing body
composition.

11. Hydrostatic weighing
• Underwater weighing
• Most common method to assess body volume
• Person’s compare regular weight with underwater weight.
• Hydrostatic underwater weighing is based on the Archimedes’ principle.
This principle states that the amount of liquid a submerged object displaces
is equivalent to the volume of the object.
• By measuring your weight on land and your weight underwater, test
administrators can calculate your body’s density
Density=Weight on land ÷ weight in water
(1 g of water = 1 cm³ by volume at 39.2F)

13. Procedure
• Prior to the hydrostatic weighing, you’ll likely be instructed to avoid
exercising or eating for at least 4 hours beforehand.
• Here’s what to expect during the procedure:
1.The test administrator measures and records your body weight on land.
2.You then slowly enter a water tank that has an underwater seat hanging
from a scale.
3.Your testing administrator instructs you to completely submerge underwater
while sitting on the chair and to breathe out fully.
4.You repeat the test three times.
• The administrator will use the average result of the three tests to calculate
your body fat percentage.

14. Draw back of hydrostatic weighing
• Time consuming
• Difficult to perform on the aquaphobic
• Requires measurement of residual lung volume
• Practically not possible to test large number of people.

15. Air displacement method
• BOD POD, A plethysmography device used to assess body volume.
• When subject is enter in to the chamber that time reduce the air volume.
• The subject sites in a structure composed of two chamber each of known volume.
• A molded fiberglass seat forms a common wall separating the front and rare
chambers.
• A volume perturbing element connects the two chambers.
• Change the pressure between two chambers oscillate the diaphragm, which
directly reflects any change in the chamber volume.
• The subject make several breaths into the air circuit to assess thoracic gas
volume.(which when subtracted from measured body volume yields true body
volume)

17. • Densitometry has its limitations, if body weight, underwater weight
and lung volume during underwater weighing are measured correctly,
the resulting body density value is accurate.
• The equation most often used to convert body density to an estimate of
relative and percentage body fat is the standard equation of siri
% body fat= (495/ D) – 450 (D= Body density)
Mass of body fat calculated by
Fat mass(kg)= body mass(kg)×(percentage fat÷100)
Fat free mass is measured by
FFM(kg)= body mass(kg) – fat mass(kg)

18. Skinfold Measurements
• Simple anthropometric procedure to measure body fat is skinfolds.
• Skinfold to estimate the body fat composition results from the close
relationship among three factors
1. Subcutaneous fat in adipose tissue deposits directly beneath the skin
2. body’s internal fat store
3. body density of the intact human body

19. • The caliper accurately measured Subcutaneous fat at selected body sites.
• Three different types of skinfold caliper.
1.Harpenden: The Harpenden Skinfold Caliper is a precision instrument
designed for use in the performance of Skinfold thickness measurements, The
Harpenden Skinfold Caliper has been used all over the world on projects of
international importance and is the most prestigious Caliper available.
2.Lange: These calipers feature spring-loaded arms providing a constant
standard pressure of 10 gm./sq.mm
3.Common plastic: The device consists of a vernier scale – metric as well as
inch measurement - with a fixed and a movable jaw
• Measuring skinfold thickness requires grasping a fold of skin and
subcutaneous fat firmly with the thumb and fore fingers and pulling it away
from the underlying muscle tissue following the skinfold’s natural contour.
• The skinfold is recorded within 2 seconds after applying the full force of the
caliper.

21. • Skin fold sites
1. triceps – vertical
2. Subscapular – oblique
3. Iliac crest – oblique
4. Abdomen – vertical
5. Thigh – vertical
6. Biceps - vertical

22. Girth measurements
• Six most common sites for girth measurement.
• Girth offer an easily administered and valid alternative to skinfolds.
Apply a linen or plastic measuring tape lightly to the skin surface so
the tape remains taut but not tight, avoid skin compression.

24. Predicting body fat from girth
From the appropriate tables in Appendix C, substitute the corresponding constants A, B, and C in the
formula shown at the bottom of each table. This requires one addition and two subtraction
steps. The following five-step example shows how to compute percentage
fat, fat mass, and FFM for a 21-year-old man who weighs 79.1 kg:
Step 1:: Measure the upper arm, abdomen, and right forearm girths with
a cloth tape to the nearest 0.25 in (0.6 cm): Upper arm =11.5 in
(29.21 cm); abdomen = 31.0 in (78.74 cm); right forearm =10.75
in (27.30 cm).
Step 2::Determine the three constants A, B, and C corresponding to the three
girths from Appendix C: Constant A corresponding to 11.5 in = 42.56;
constant B corresponding to 31.0 in =40.68; and constant C corresponding to 10.75 in = 58.37

25. Step 3:: Compute percentage body fat by substituting the appropriate
constants in the formula for young men shown at the bottom of Chart 1
in Appendix C as:
Percentage Fat =Constant A + Constant B - Constant C -10.2
= 42.56+40.68-58.37 –10.2
= 83.24-58.37 – 10.2
= 24.87 – 10.2
=14.7%
Step 4:: Calculate the mass of body fat as:
Fat mass =Body mass (% Fat /100)
= 79.1 kg ×(14.7 / 100)
=79.1 kg × 0.147
= 11.6 kg
Step 5:: Determine FFM as:
FFM = Body mass -Fat mass
=79.1 kg - 11.63 kg
= 67.5 kg

26. Bioelectrical impedance Analysis(BIA)
• Bioelectrical impedance analysis (BIA) is a commonly used method for
estimating body composition, in particular body fat and muscle mass or for weight
loss goal. In BIA, a weak electric current(1-10 μA) flows through the body and
the voltage is measured in order to calculate impedance (resistance) of the body.
Most body water is stored in muscle. Therefore, if a person is more muscular there
is a high chance that the person will also have more body water, which leads to
lower impedance.
• Bioelectrical impedance analysis devices are considered safe for most people.
However, BIA should not be used by anyone with an electronic medical implant,
such as a heart pacemaker or an implantable cardioverter defibrillator (ICD). Also,
most device makers recommend that the products not be used by pregnant women.

27. Some factors that may affect a reading when you use a BIA scale.
• Body weight. Bioelectrical impedance analysis may be less accurate in obese people.
• Hydration level. Dehydration may cause fat-free mass (muscle and bone) to be
underestimated.
• Recent exercise activity. High-intensity exercise may affect the accuracy of BIA
readings.
• Recent food or drink intake. some study suggest that BIA may be more accurate after
overnight fasting.

29. Ultrasound
• Assess the thickness of different tissue.
• Obtain an object of deeper tissue such as a muscles cross sectional area
• The method converts electrical energy through a prob into high frequency
sound waves that penetrate the skin surface in to the underlying tissues.
• The sound wave pass through the adipose tissue and penetrate the muscles
layer and then reflect from the fat muscle interface after the reflection from
a bony surface to produce an echo,which return to a receiver within the
probe.

30. Dual-Energy X- Ray Absorptiometey
Dual-energy x-ray absorptiometry (DXA),a high-technology procedure shown in
Figure to assess bone mineral density in osteoporosis screening can also quantifies
fat and muscle around bony areas of the body, including region without bone
present. When used for body composition assessment, DXA does not require
assumptions about the biologic constancy of the fat and fat-free components as
does hydrostatic weighing.
Two distinct x-ray energies with short exposure with lowradiation dosage
penetrate into bone and soft tissue areas to a depth of about 30 cm. Specialized
computer software reconstructs an image of the underlying tissues. The computer
generated report quantifies bone mineral content, total fat mass, and FFM. DXA
also can target selected body regions for more in-depth analysis.

32. OTHER LABORATORY TECHNIQUES
• Many other laboratory techniques are available for assesing body
composition.
1. Near Infrared interactance
2. CT scan
3. MRI

33. Reference
• Essentials Of Exercise Physiology (Old) by William D. McArdle BS
M.Ed PhD, Frank I. Katch , et al.
• Physiology of Sport and Exercise by W. Larry Kenney , Jack H.
Wilmore, et al