Body Composition Flashcards
Body composition focuses on techniques to measure…
- body fat
- lean body mass
- fat free mass
Direct body composition:
- chemical analysis
- cadaver analysis
Indirect body composition:
- hydrostatic weighing
- skinfolds
- BIA
- etc.
Body composition is the separation of ____ ____ into _____ _____.
- bodily tissues
- quantifiable compartments
____ compartment model is most common.
2
2 compartment model divides body into:
- fat vs FFM (essential
- fat removed) or lean body mass (includes essential fat)
Nonessential fat is….
adipose tissue
Essential fat is….
intra organ/muscle/other tissues
FFM and LBM includes…
- muscle
- bone
- organs
- etc.
Fat has a density of _____g/ml.
0.900 g/ml
FFM has a density of ______ g/ml.
1.100 g/ml
Why can there be error with 2 compartment model?
assuming fat and FFM density
Multiple compartment models:
models that account for more than 2 body compartments
The greater number of body compartments accounted for, the greater the…
reduction of error
Example of multiple compartment model:
- Dual Energy X-ray Absorptiometry (DEXA)
- 3 compartments: fat, soft tissue, bone
- the measurement of bone density significantly reduces the error associated with amount of variation in bone density among individuals (aging)
Hydrostatic weighing is based on _____ ____.
Archimedes’ Principle
Archimedes’ Principle:
- any object immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object
- not to be confused with the volume of fluid displaced by an object
For hydrostatic weighing, we must know….
- residual volume
- density of water
- trapped gas (GI)
- dry body weight
- submerged body weight
Residual volume is calculated based on…
- height
- age
- sex
Density of water varies with _____.
temperature
Trapped gas (GI) is approximated to be ____ mL.
100 mL
Dry body weight is with…
- minimal clothing
- minimal trapped air
Submerged body weight is with…
- same clothes
- minimal trapped air
Minimum equipment required for hydrostatic or underwater weighing technique:
- body of water
- accurate hanging scale
- thermometer
- water density table/calculator
- may need weights to assist with submersion
- body density (BD) calculation
BD =
dry weight / [((dry weight - wet weight) / water density) - total gas volume]
Procedure for hydrostatic weighing:
- full end expiration and submersion for 5-10s
- minimize movement
- repeat 5-10 times
Several formulas have been derived by a variety of research to predict _____ from BD.
% body fat
% body fat can be used to calculate…
- fat mass (kg)
- lean body mass (% or kg)
Siri (1961):
% fat = (4.95/BD) - 4.50 * 100
Brozek (1963):
% fat = (4.57/BD) - 4.142 * 100
Lohman (1986):
% fat = (5.3/BD) - 4.89 * 100
Limitations of hydrostatic weighing:
- assumption of the constant density of body fat and LBM
- assumption of the magnitude of trapped air: GI tract, lung, body cavity
- variability in body mass determination
- number of trials performed
Possible ____% (_____) error in body fat prediction is possible due to the variability in the density of ____ ____ ____ in women.
- 19% (relative)
- LBM
Possible ____% (_____) error in body fat prediction based on the variability in ____ volumes alone.
- 8% (relative)
- lung
How is variability in body mass determination a limitation?
in air, things such as hydration/dehydration, nutritional status can influence calculation
Accuracy of hydrostatic weighing is enhanced if ____ trials are done.
9-10
Hydrostatic weighing: if all factors are carefully controlled, repeated measurement of % fat from UW varies approx _____.
- +/- ~3%
- range 2.5-3.8%
Reliability of hydrostatic weighing:
- can be good
- test/retest r = 0.98
In hydrostatic weighing, there is limited ____ measurements done, so ____ is difficult.
- direct
- validity
Hydrostatic weighing as an _____ measure is considered to be ____.
- indirect
- valid
BodPod is aka…
air displacement plethysmography
BodPod uses the same theory as ____ _____, but uses ____ _____.
- hydrostatic weighing
- air displacement
BodPod is _____.
automated