Assessing Body Composition Flashcards
3 reasons to assess body composition?
- clarify disease risk
- sport performance
- weight management
What common measures of body composition does CSEP use?
BMI and waist circumerence
What common measures of body composition records % body fat?
- densitometry
- DEXA
- Bioelectrical impedance
- Skinfold measurements
What indirect measure of body fat did we learn in lecture?
BMI = kg / m²
What does BMI not account for?
composition of fat mass vs FFM
The correlation of BMI with hydrostatic weighing (the gold standard) is r = ?
0.70 - okay but not the best, > 0.80 is the best
____ is widely used to identify at-risk individuals
BMI
What is one fault of BMI?
there are possible misclassifications of underweight, overweight, and obese status
___ ___ is often used along with BMI
waist circumference
Waist circumference is an (direct/indirect) assessment of abdominal adipostiy
indirect
What method do you use when measuring waist circumference?
the cross-handed method
What is the arm position (1) and the tester position (2) during a measure of waist circumference?
(1) across chest upon shoulders
(2) off to the side of the participant - usually on the right hand side
Pros and cons of waist circumference?
PRO - easy and quick, and can also be used in conjunction with BMI
CONS - limited
When do you take the waist circumference reading?
do the reading at the end of exhalation
BMI ranges for: Underweight = Normal Weight = Overweight = Obese Class I = Obese Class II = Obese Class III =
Underweight = < 18.5 Normal Weight = 18.5 - 24.9 Overweight = 25 - 29.9 Obese Class I = 30 - 34.9 Obese Class II = 35 - 39.9 Obese Class III = > 40
T/F: Resistance trained clients who have a BMI in the overweight category but a WC below the cutoffs are unlikely to be at increased health risk
True!
_______: measurement of the size and proportion of the human body
anthropometry
Pros of girths, widths, and breadths?
simple
inexpensive
well suited for large surveys
minimal skill & training
What is the only direct measure of measuring body composition?
cadaver analysis
What are three key limitations of skinfold measurements?
- Client sensitivity to having SKF measured
- Substantial intra and inter-tester variability in SKF thickness
- Time requirements for training, practice, and accurate administration
relative body fat (%BF) is used for classification of body fatness. What are the healthy ranges and obese ranges for both men and women?
MEN: Healthy - teens Obese - > 22-25% WOMEN: Healthy - twenties Obese - > 35-38%
What is a major limitation of using relative body fat %?
you can get drastically different % of body fat due to different sites on the body
_____ estimates body density by determining the ratio of body mass to body volume
densitometry
what is the formula for densitometry?
BD = BM/BV
What are the two methods of densitometry?
- Hydrostatic weighting (hydrodensitometry)
2. Air displacement plethysmography (Bod Pod)
What body type will have a higher underwater weight?
leaner people
“criterion measure used for development of %BF prediction equation and validation of field measurements”
hydrostatic weighting
what type of %BF compares dry land weight to underwater weight?
hydrostatic weighing
what is the formula for body volume using hydrostatic weighing?
[(dry weight - underwater weight) / density of the water] - (RV + 100mL)
What is the formula for body density using hydrostatic weighing?
dry weight / body volume
Cons of hydrostatic weighing?
- residual air in lungs/GI tract will affect reading
- you must be comfortable in water to use this
- need lots of trials
- $$$$ - need the proper equiptment
Siri vs Brozek formulas for %BF using BD?
Siri - (4.95/BD-4.5)x100
Brozek - (4.57/BD-4.142) x 100
What is the %BF for a participant who has a body density of 1.065 g/cc? (use Siri and Brozek formulas)
Siri = (4.95/1.065-4.5)x100 = 14.8%
Brozek - (4.57/1.065-4.142) x 100 = 14.9%
The two-component model is the foundation for many techniques to measure % body fat, what is the formula?
body mass = fat mass (FM) + fat-free mass (FFM)
Densities of FM and FFM are the same for all individuals, what are they?
FM - 0.901g/cc
FFM - 1.100g/cc
Using the two-component model, how do individuals differ in their scores since FM and FFM densities are the same for all individuals?
they differ from the reference body only in the amount of fat (as the proportional contribution of FFM components are constant)
Water = 73.8%
Minerals = 6.8%
Protein = 19.4%
These numbers are for relative body composition - they are taken from the results of one study that was done in the 60’s on all white middle aged men. What is the problem with this?
That represents such a small % of the population demographic of the world - it is unfair to assume that these numbers are the same for everyone!! Also, the study is sooooo old its probs super outdated.
FFM density can vary substantially according to what 6 things?
- age
- gender
- physical activity level
- ethnicity
- relative proportion of water and mineral
- level of fatness
“improve estimation of %BF by replacing ‘reference body’ with a population specific body that takes into account age, gender, ethnicity, and level of physical activity”
multicomponent models
What method gets body density by using body volume by air displacement instead of water?
air displacement plethysmography
“2 chambers separated by a fiberglass wall”
air displacement plethysmography
Front = client sits Back = reference chamber
How does air displacement plethysmography work?
compares volume pressure of from chamber with the reference chamber to determine the volume of the individual
Pros and Cons of the Bod Pod?
PRO: -quick (5-10min) -requires less skill -reliable (r=0.9-0.96) -requires minimal client cooperation CON: -size restraint cause of chamber size -must have approved clothing and swim cap -no beards
“uses x-rays and a 3-component model of assessment”
DEXA
what is the formula for DEXA?
bone mineral mass + bone free lean tissue + fat mass = total body weight
Attenuation of x-rays used during DEXA are dependent on what three things?
thickness, density, and composition of tissues
Pros and Cons of DEXA?
PRO: -gaining recognition as criteria measure -safe (low radiation) -quick -minimal client cooperation -reliable (r>0.95) CON: -different manufacturers have different models -may require licensed technician -clients may not fit in dimensions of the bed
What are other field methods of body compositions that are more practical for estimating body composition compared to laboratory methods?
bioelectrical impedance analysis (BIA) and skinfolds (SKF)
“measures resistance to electric current to estimate %BF”
bioelectrical impedance
resistance to electric current for muscle cells compared to fat cells?
muscle cells = 75% water
fat cells = 5-13% water
Water reduces resistance and current moves more easily through ____ tissue
leaner
Dehydration or adipose tissue slows the current, especially in ____ tissue
fat
_____ ____ determines resistance of tissues to flow of electrical current
hydration level
Pros and Cons of bioelectrical impedance?
PRO: -fairly inexpensive -easy to administer -quick results CON: -variability (3-8%) -pre-test guidelines are intense to follow -which pathway does electricity take?
What are the 4 pre test guidelines for BIA?
- no eating or drinking within 4 hours of test
- no exercise within 12 hours
- no alcohol within 48 hours
- urinate within 30 minutes of the test
Skinfold measurements are correlated with body density from hydrostatic weighing, and have an r of?
0.76
SKF’s indirectly measure thickness of subcutaneous adipose tissue, what are some common sites?
subscap suprailiac abdominal chest arm thigh medial calf
What are the 4 assumptions of SKF measurements?
- Good measure of subcutaneous fat (12-site SKF and MRI has strong correlation)
- Fat distribution is similar for all individuals within each gender
- Relationship between sum of SKF and body density
- Sum of SKF can be used to estimate total body fat
It is estimated that ___ of body fat is subcutaneous.
1/3
SKF Procedures:
Measurements are taken on the ____ side of the body.
right
What is a major source of error in test administration for SKF?
landmarking sites accurately
SKF Procedures:
The caliper is ____ to the fold and __cm above/below fingers.
perpendicular; 1cm; below
SKF Procedures:
When taking the measurement, continue to grasp and elevate the fold, taking reading __ seconds after releasing the caliper tension
3
For SKF you should be taking a minimum of __ measures at each site (+/-__mm) and take the mean value
2; 5
Pros and cons for skinfolds?
PRO:
-relatively inexpensive
-easy to administer by trained individuals
-can estimate %BF
-reliable (r=0.9) with experienced testers
CONS:
-requires practice
-limited population (doesn’t work on fat people/tight fascia)
-variability in equations
What type of calipers are better?
plastic have less precision and do not exert constant pressure through range of measurement
what does SO5S stand for?
sum of 5 skinfolds
formula for fat weight?
total weight x %BF
formula for lean weight?
total weight - fat weight
formula for target weight?
lean weight / [(100% - desired fat %)/100]
Your client weighs 200 lbs and has 25% body fat. What is their ideal weight if their goal is to reach 15% BF?
Target weight = 176 lbs
