Chapter 8 (Assessing Body Composition) Flashcards
Body fat is essential for what?
- thermal insulation
- storage of metabolic fuel
- transport of fat-soluble vitamins
Define body composition
- the measurement of fat mass versus fat-free mass
Recommendations of body fat percentage for females
- 10% - 28%
Recommendations of body fat percentage for males
- 3% - 22%
What are the uses of body composition measurements?
- formulate nutritional recommendations
- disease risk
- monitoring risk
- assessing changes
Multiple theoretical models estimate what?
- % body fat
What are the two components of % body fat?
- fat mass
- fat-free mass
What is the density of fat mass?
- 0.901 g/cc
What is the density of fat-free mass?
- 1.100 g/cc
Fat-free mass components
- 73.8% water
- 19% protein
- 6.8% mineral
What aspects affect the components of fat-free mass?
- age
- sex
- ethnicity
- physical activity
- % body fat
Most accurate body composition models
- multi compartment models
What is densitometry?
- body density
- Db = BM / BV - body volume is obtained through hydrostatic weighing or air displacement
What is an x-ray for body fat?
- dual energy x-ray absorptiometry (DEXA)
- CT
What is hydrostatic weighing (hydro densitometry)?
- Body volume calculated by displacement of water
- body density calculated by weight above and below water
What principle is hydrostatic weighing based on?
- Archimedes’ principle
What law is the bod pod based on?
- Boyle’s law of pressure volume relationship
What does the dual x-ray absorptiometry (DEXA) measure?
- densitometry
- bone mineral
What Clinical method shows the distribution of fat?
- DEXA
What clinical method best estimates mineral contribution to free-fat mass?
- DEXA
What are examples of 3 component free-fat mass clinical tests?
- CT scan
- MRI
What are manual field methods for testing for body fat?
- skinfold
- anthropometry
What are electrical equipment field methods for testing for body fat?
- ultrasound
- bioelectrical impedance analysis
An indirect measurement of subcutaneous body is the definition of what field method?
- Skinfold
Skinfold are not great because of what?
- overestimates %BF in leaner clients
- underestimates %BF in obese clients
What are the major sources of error in a skinfold?
- technicians skill
- SKF caliper
- client factors
What is a bioelectrical impedance analysis? (BIA)
- a combination of pairs of sending and receiving electrodes
What is the impedance for fat and lean tissue?
- fat: electrodes flow slower (with resistance)
- lean: electrodes flow faster/easier
What is the main influential factor in BIA?
- hydration levels
Potential disadvantage to BIA
- cannot distinguish intracellular and extracellular water
Participates should do what before using the BIA?
- no eating/drinking before
- no alcohol or caffeine - no exercise before
- using the bathroom
(women can not be on their period)
What is the anthropometric method?
- measurement of the size and proportion of the human
Downside to the anthropometric method
- does not separate fat and muscle
What is circumference?
- measurement of the girth at prescribed landmarks
Waist-to-hip ratio
- indirect measure of lower and upper body fat
Waist- to-height rule of thumb?
- waist should be less then 50%
