Body Composition
Exercise Physiology
McArdle, Katch, & Katch – Ch. 16
Gross Composition of Human Body
Body composition analysis often focuses on the tissue and
whole body levels of multi-component model.
Behnke’s Reference Man
 Storage fat averages ___% of body mass for young men.
 Essential fat averages ___% of body mass for young men.
Reference Woman


Storage fat averages ___% for young adult women.
Essential fat averages ___% for young adult women.
Four times greater essential fat for females relates to child-bearing.
Gross Composition of Body
 Essential fat: fat in organs, muscle, CNS, bone
marrow. Also includes sex-specific essential fat
necessary for survival.
 Storage fat: energy reserve includes visceral
adipose tissue & larger subcutaneous depots.
 Fat Free Body Mass and Lean Body Mass
 In vivo (within a living organism), it isn’t possible to
differentiate between essential and non-essential fat.
 LBM =FFM (bone, muscle, organs, connective tissue) +
essential fat. LBM is an in vivo entity.
 Density of human fat is .901 g/cm3. FFM varies.
Gross Composition of Body
 Density of FFM
lower in children
than adults.
 Female density of
FFM is lower at each
age than male.
 Percentage of FFM
that is composed of
water is higher in
children.
Gross Composition of Body
 Minimal body mass
 What is suggested “healthy” lower level % fat in ?
3%
 In females, includes 3% essential fat (same as )
+ 9% sex-specific essential fat = 12%.
 Optimal range of body fat should be established for
each sport.
 Elite female athletes in ballet, gymnastics, rowing,
skating, track running events, triathlon body fat 815%
 Underweight ≠ thin; appearance may average
18.2% body fat.
Leanness, Exercise, and Menstrual
Irregularity
 Lean:fat ratio may play role normal menstrual
function.
 Peripheral fat’s role in angrogens to estrogen
 Production of leptin in adipose tissue
 Factors associated with menstrual irregularity
 High levels chronic physical stress causes hormone
cascade
 Nutritional inadequacy to sustain pregnancy
 Too little fat triggers metabolic disturbances
 Regional fat deposition
Methods of Body Composition
Direct Assessment
 Chemical dissolution: dissolves body
into fat and fat-free components
 Physical dissection: extensive
dissection of cadavers.
Indirect Body Composition
 Hydrostatic
Weighing
 Air Displacement
 Skinfolds
 Girth
Measurements
 Bioelectrical
Impedance
Analysis
 Dual-Energy X-Ray
Absorptiometry
 Near Infrared
Interactance
 Ultrasound
 Computed
Tomography
 Magnetic
Resonance Imaging
Hydrostatic Weighing
How is Archimedes principle of
water displacement used to
evaluate body composition?
Loss of weight in water equals
weight of water displaced
which yields volume of water
displaced @ any temperature.
Example: 50 kg  2 kg @ 39.2F
48 kg @ 39.2F = 48,000 cm3
50 kg ÷ 48,000 cm3 = 1.0417g/cm3
Hydrostatic Weighing
 Body Density = Mass ÷ Volume
 Computing % body fat using
population specific equation.
 Limitations and Errors.
 Air compartments in body.
 Densities of FFM vary due to race, age,
and athletic experience.
Air Displacement
 Air displaced = Body Volume
 Body density = mass ÷ volume
 High validity compared to hydrostatic
weighing
Skinfolds
 Common field method
 Relationships among
selected skinfold sites
and body density
 Caliper exerts constant
tension of 10 g/mm2
 Sum of skinfolds
indicates relative
fatness of individual
Girth Measurements
 Uses 3 sites: see Appendix F
 Men: right forearm, abdomen, right
upper arm (<27) or buttocks (27+)
 Women: abdomen, right thigh, right
forearm (<27) or right calf (27+)
 Pattern of fat distribution
 Predicting Body Fat
Bioelectrical Impedance
Hydrated, fat-free
body tissues and
extracellular water
facilitate electrical
flow compared to
fat tissue because
of greater
electrolyte content
of fat-free
component.
Dual Energy X-Ray Absorptiometry
 Two distinct x-ray energies penetrate
into bone & soft tissue areas to depth
of 30 cm. Computer software
reconstructs an image of underlying
tissue.
 Quantifies bone mineral content, total
fat mass, and FFM.
Body Mass Index
 Importance of this easy to obtain index is
its curvilinear relationship to all-cause
mortality.
Near-Infrared Interactance
 Uses technology developed by U.S.
Dept. Agriculture to assess body
composition of livestock and lipid
content of grains.
 Does not accurately predict human
body fat across broad range of body
fat levels.
Ultrasound
Measures:
1. Assess thickness of different tissues
2. Obtain image of deeper tissues, e.g.
muscle’s cross sectional area
 It works by converting electrical
energy through a probe into high
frequency pulsed sound waves that
penetrate the skin surface to fatmuscle interface.
Computed Tomography
 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
Magnetic Resonance Imaging
 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.
Average Values for Body
Composition
 Average young male possesses
between __ and __% fat.
 Average young female possesses
between ___ and ___ % fat.
Goal Weight
 Goal weight should be based on body
composition not stature.
 Goal Weight = Fat Free Body ÷ (100 % Desired Body Fat)
 Desirable Fat Loss = Present body
weight – Goal body weight
Percentage of Body Fat




Ballet dancers: 13-20
Body builders: 10-15
Triathlon: 10-15
Jumpers: 10-18
Illustration References
 McArdle, William D., Frank I. Katch,
and Victor L. Katch. 2000. Essentials
of Exercise Physiology 2nd ed. Image
Collection. Lippincott Williams &
Wilkins.
 Plowman, Sharon A. and Denise L.
Smith. 1998. Digital Image Archive
for Exercise Physiology. Allyn &
Bacon.