body composition
Hydrostatic (underwater) weighing
Criterion measure for determining body composition through the calculation of body density
calculating body density from hydrostatic weighing
DB= MA/[(MA - MW)/DW -(RV+VG)]
Hydrostatic weighing
This method has the advantage of needing no volume information of the body (except residual volume). The procedure is based on Archimedes' principle, using the following three measurable values: The weight of the body outside the water the weight of the immersed body and the density of the water
average % body fat males
average 12-15%
average % body fat females
average 25-28%
BMI
body mass index
2nd formula
calculates desired weight (WT2)
3rd formula
calculates the amount of weight to be gained or lost
Dw
density of water
1st formula
determines the amount of FFW an individual currently has (WT1).
FFW
fat free weight
lean body mass
includes all fat-free mass along with essential fat. Lean body mass is difficult to measure so the fat mass/fat-free mass model is most often used
Fat-free mass
is composed of all of the body's nonfat tissue including bone, muscle, organs, and connective tissue.
low resistance
lean tissue
Ma
mass in air
Mw
mass in water
volume
mass/body density
body density
mass/volume
RV
residual volume
VG
volume of gastrointesinal air
density of body
weight of body is equal
weight of body weight of body
weight of immersed body
Siri
%BF = [(4.950/DB)-4.50]*100
Brozek
%BF =[(4.570/DB)-4.142]*100
calculate %FFW
%FFW = 100% - %Body Fat
Laboratory techniques
1. Hydrostatic (Underwater) Weighing, 2. Densitometry, 3. Dual energy X-ray absoptiometry, 4. Bod Pod
health risks of over weight and obesity
1. Hypertension (high blood pressure) 2. Cardiovascular disease 3. Gallbladder disease and Hypercholesterolemia 4. Diabetes mellitus 5. Cancer 6. Miscellaneous disorders
Field tests
1. skinfolds 2. height and weight 3. body mass index 4. waist-to-hip ratio 5. Bioelectrical impedance (impedance plethysmography)
WT2
100 x FFW/ 100% - %BF
essential fat females
12-15%
normal
20-24
overweight
25-29
essential fat males
3%
obese
30-39
underweight
<20
FFW
=WT1 x (100%-BF%/100)
extreme obesity
>40
Bod Pod
Air displacement plethysmography
Brozek formula
At lower densities, the Siri formula gives increasingly higher %BF values than the
BMI calculations
BMI = wt(kg)/ht(m)2
Types of body composition
Fat-free mass, lean body mass
Average % body fat
Males - 12-15% Females 25-28%
Essential fat
Males - 3% Females - 12-15%
waist-to-hip ratio
Predictor of chronic disease risk Assesses fat pattern and distribution
Dual energy X-ray absorptiometry
Separates lean body mass, fat mass "Gold standard" for bone density Allows for simultaneous measurement of fat and lean soft tissue
Skinfolds
The double thickness of skin the adipose tissue between the parallel layers of skin Assumption 30-50% of total body fat located subcutaneously Age, gender, degree of fatness affect fat distribution
Mw
The highest consistent weight is selected from the trials, and the weight of the apparatus, called the tare weight, is then subtracted from the scale weight.
Densitometry
The measurement of mass per unit volume
body composition
The partitioning of body mass into fat-free mass (weight or percentage) and fat mass (weight or percentage)
Archimedes' Principle
The principle that a partially or fully submerged object will experience an upward buoyant force equal to the weight or the volume of fluid displaced by the object
Bioelectrical impedance (impedance plethysmography)
Varying resistance to electrical current Adipose tissue High resistance Lean tissue Low resistance
change in WT
WT2-WT1
fat
adipose tissue
high resistance
adipose tissue