Transcript BodyComposition.ppt

Body Composition
Fat -free mass
Body Fat
essential
non-essential
Further divide body into
components
fat
water
bone
muscle
organ tissue
other (nerves, connective tissue, etc)
Ideal Body Composition
health
aesthetics
performance
Healthy fat percentage
16-25% for females
< 20% for males
Aesthetic body composition
lean look is prized and admired
desire can lead to eating disorders
Performance body composition
sport-specific
some sports have specific weight classes
wrestling, boxing, weight lifting
variability depends on the metabolic
requirement of the activity and on the
disadvantage of carrying extra weight
problems when individuals try to gain too
much weight or lose too much
Measuring Body Composition
Two component models
hydrostatic weighing (underwater)
skinfolds
Multiple component models
BIA
DXA
TOBEC
Biochemical
Assumptions of measuring
composition
dissection is most accurate
most indirect methods are based on
cadaver studies
cadaver studies: small n (8), one female
fat mass 0.901 gm/ml
fat-free mass 1.100 gm/ml
Cadaver studies
original work in 1940s
did not compare to other methods, just
direct measurement
assumed density of 1.100 gm/ml
extrapolated to humans from guinea pigs
until can validate a method directly, it is an
estimate
all of the methods have limitations
Hydrostatic Weighing
Until DXA, most accurate method
based on Archimedes’ Principle of water
displacement and density
procedural difficulties
Dual Energy X-Ray
Absorptiometry
developed to determine bone content and
subsequently, density
may replace hydrostatic weighing as the
gold standard
relies on fewer assumptions about human
tissue
can use animals to directly validate the
technique
Biochemical Techniques
potassium analysis
total body water
intert gas absorption
Anthropometric and Skinfolds
BMI
Waist Circumference and Waist-Hip Ratio
Somatotype
Anthropometric
Skinfolds
Ultrasound, Computerized
Tomography (CT), and Electrical
Impedance
ultrasound: technology used by
cardiologists, estimate thickness of tissues
CT: x-ray that provides a threedimensional view of the body
Total Body Electrical Conductivity
(TOBEC): surrounds body with
magnetic field and measures the rate at
which the body conducts electrical
energy
Bioelectrical Impedance Analysis (BIA):
measure impedance to flow in opposite
extremities