Body Composition: Basic Concepts and Techniques Flashcards

1
Q

What does body composition mean?

A
  • ratio of body fat to lean body mass

- amount of bone, fat, muscle tissue

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2
Q

5 levels of complexity for body composition models:

A
  1. atomic
  2. molecular
  3. cellular
  4. tissue-organ
  5. whole-body
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3
Q

Sum of components at each level =

A

body mass

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4
Q

_____ are the building blocks that form the whole body.

A

elements

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5
Q

6 elements that make up 98% of body weight:

A
  • oxygen
  • carbon
  • hydrogen
  • nitrogen
  • calcium
  • phosphorus
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6
Q

____ elements make up the other 2% of body weight.

A

44

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7
Q

6 major compartments of molecular level:

A
  • water (intra + extracellular)
  • protein (N containing compounds that form metabolic tissue in body)
  • lipid
  • carbohydrates (glycogen) = negligible
  • bone minerals
  • soft tissue minerals
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8
Q

Water is ____% of total body weight.

A

60%

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9
Q

Bone minerals and soft tissue minerals make up ____% of body weight.

A

5%

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10
Q

Label FM or FFM:

  • lipid
  • water
  • protein
  • carbohydrates
  • soft tissue minerals
  • bone minerals
A
  • lipid (FM)
  • water (FFM)
  • protein (FFM)
  • carbohydrates (FFM)
  • soft tissue minerals (FFM)
  • bone minerals (FFM)
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11
Q

Lean soft tissue consists of:

A
  • metabolic tissue
  • intracellular water
  • extracellular water
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12
Q

Cellular level is comprised of:

A
  • cells
  • extracellular fluids (interstitial fluid and plasma)
  • extracellular solids (bone minerals, collagen and elastic fibres)
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13
Q

BCM:

A
  • body cell mass
  • used to reflect the metabolic tissues and intracellular water
  • site for most metabolic processes in the body
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14
Q

Tissue-organ level is comprised of:

A
  • adipose tissue
  • skeletal muscle
  • bone
  • visceral organs
  • brain
  • heart
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15
Q

Components of adipose tissue:

A
  • subcutaneous
  • visceral
  • interstitial
  • yellow marrow
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16
Q

Whole body level consists of:

A
  • body size
  • body shape
  • exterior characteristics
  • physical characteristics
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17
Q

The 5 level organization model of body comp provides the framework for understanding the different _____ available to assess body comp.

A

methodologies

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18
Q

Anthropometry is used to determine ____ ____ and _____.

A
  • body size

- proportions

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19
Q

5 components of anthropometry:

A
  • height
  • weight
  • BMI
  • circumferences
  • skinfold thickness
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20
Q

Why does height need to be accurate?

A
  • used for energy requirement calculations
  • used for BMI
  • used for height/weight tables
  • measure if possible
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21
Q

What is the most important anthropometric measure?

A

weight

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22
Q

Weight is related to ____, not ______.

A
  • size

- composition

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23
Q

____ ____ are most accurate to measure weight. ____ status is found.

A
  • electronic scales

- fluid

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24
Q

BMI evaluates ______ relative to _____ _____.

A
  • weight

- health risk

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25
BMI =
weight (kg)/height (m^2)
26
Interpretation of BMI:
- different values at age 65 | - association with health risks
27
Why might BMI not tell the whole story?
- tables not separated by sex, age - females have more fat at same BMI than men - not a good measure in elderly - can remain at same weight and still gain fat
28
Circumferences are used to estimate.....
- skeletal muscle mass | - body fat stores
29
Waist circumference correlates with ____ ____ ____.
visceral fat stores
30
Waist circumference is a useful index of ____ _____, _____ _____.
- abdominal obesity | - metabolic syndrome
31
Increased risk for ____ and ______ in overweight/obese individuals (males > ____ ", females > ____").
- CVD - type 2 diabetes - 40" - 35"
32
Waist to hip ratio estimates .....
distribution of subcutaneous and intra-abdominal adipose and muscle tissue
33
Bad waist to hip ratios (males > _____, females > ____) can possibly increase risk for ____ and ______.
- 1.0 - 0.8 - morbidity - mortality
34
Advantages of body circumferences:
- mobile - inexpensive - fast, repeatable - non-invasive - no formal training - useful for large samples - anthropometrics and body comp values to which they relate are strongly linked to health
35
Disadvantages of body circumferences:
- limited accuracy - training - repeatability (WC and skinfolds)
36
Skinfold thickness is the measurement of ....
subcutaneous adipose tissue stores
37
Skinfold thickness is measured with _____.
calipers
38
Adipose stores vary with ____, _____, ____.
- age - sex - race
39
When doing skinfold thickness, using ____ ____ is more representative than only ____ _____.
- multiple sites | - one site
40
Skinfold thickness needs to be done by _____ _____.
trained individuals
41
Advantages of skinfold thickness:
- simple, fast, inexpensive, portable - good reference data - can be used with estimation equations - best field technique for FM estimation (strongly correlate with % BF)
42
Disadvantages of skinfold thickness:
- includes skin and SAT - affected by compressibility of SAT - maximum jaw openings - low precision - training and experience essential - poor correlation with FFM
43
BIA stands for:
bioelectrical impedance analysis
44
BIA estimates what 3 components of body comp?
- total body water - FFM and FM - body cell mass
45
How does BIA work?
- low level electrical current passes through the body - FFM = electrical conductor - FM = insulator
46
BIA is based on the relationship of ____ _____ to the ___ ____ of the body.
- body comp | - water content
47
FFM has high ____ and ____ content, it is ____ resistant to flow of the electrical current.
- water - electrolyte - less
48
Impedance:
opposition of a conductor to the flow of an alternating electric current (ie resistance to flow)
49
Advantages of BIA:
- safe - potentially portable - useful longitudinal observations - variable instrument cost
50
Disadvantages of BIA:
- measurement sensitive to subject conditions such as hydration and recent activity - instrument predictions may be population specific
51
Gold standard for body comp:
DEXA
52
DEXA stands for:
dual energy X-ray absorptiometry
53
DEXA is a ___ compartment:
- 3 - bone mineral density - lean soft mass - total and regional body fat
54
DEXA uses ___ ___ ___ and is ___ _____.
- low dose radiation | - non invasive
55
Exclusions for DEXA:
- pregnancy | - pt > 300 lbs
56
How does DEXA work?
low radiation x-rays of 2 different photon energy levels pass through the body and are identified by a photon detector that measures the amount of energy absorbed
57
ASM =
appendicular skeletal muscle
58
Advantages of DEXA:
- fast, non invasive - convenience and comfort, to pre-test protocol - direct quantification of body comp - values for bone density and mass - safe for serial measurement (low radiation) - regional and whole body measurements
59
Disadvantages of DEXA:
- height and weight restrictions - requires licensed technician - operator error - cannot compare data from different manufacturers' machines - not mobile - high cost to purchase and operate - cannot specifically discern skeletal muscle mass and quality (like CT/MRI)
60
Densitometry divides the body into ___ compartments:
- 2 - FM - FFM
61
Densitometry measures ___ _____.
body volume (V)
62
Densitometry uses ____ to calculate ___ _____, because density =
- volume - body density - mass/volume
63
2 ways to do densitometry:
- hydrostatic weighing | - bod pod
64
Assumptions in densitometry:
- FM density = 0.901 g/ml - FFM density = 1.10 g/ml - densities of FM and FFM components (water, protein, mineral) are the same for all individuals - proportion of the FFM components are constant within an individual
65
Hydrodensitometry:
- underwater weighing | - subject exhales upon submission in tank
66
In hydrodensitometry, body volume =
loss of weight in water
67
Archimedes principles:
- volume of submerged object = volume of water displaced | - weight - weight underwater = weight of water displaced
68
BV (hydrodensitometry) =
BW - UBW
69
BD (hydrodensitometry) =
BD = BW/BV
70
Advantages of hydrodensitometry:
- small error (equivalent to 2% BF) - Well studied - few safety concerns
71
Disadvantages of hydrodensitometry:
- operators require significant training - measurement is difficult - not suitable for children, elderly, disabled - people unwilling/unable to submerge in water - not mobile - residual volume is major source of error in density and %BF
72
Bod Pod is aka...
air displacement plethysmography
73
Bod pod estimates ____ from measured ____ ____. Subject seated in a _____ chamber.
- % BF - body volume - fiberglass
74
How does bod pod work?
- measures body volume by air displacement - measures pressure changes with injection of known volume of air into closed chamber (pressure changes used to measure volume)
75
Body volume (bod pod) =
volume of air the subject displaces inside an enclosed chamber
76
Bod pod test procedures:
- subject sits inside bod pod chamber for 2 x 1 minute measurements - bathing suit and swim cap
77
Pre-test protocol for bod pod:
- relaxed - no eating, drinking, exercise 2 h pre-test - void bladder - no moisture on body, hair, swimsuit - minimal or consistent facial hair
78
Advantages of bod pod:
- Fast, non-invasive - Precise, simple to operate, rapid (minimal training required) - Accommodates a variety of populations: obese, elderly, children, disabled, infirm - No safety concerns - Small error - Somewhat mobile, may be suitable for field testing - Suitable for patients up to 500 lbs, up to 7 ft tall
79
Disadvantages of bod pod:
- pre-test protocol - lung volume must be estimated if measurement is difficult - subject discomfort related to wearing bathing suit/tight fitting clothes, claustrophobia - only one commercially available system
80
Only means of measuring level 4 (tissues and organs) is....
imaging
81
Imaging estimates tissue ____ and ____.
- quantity (area, volume, mass) | - quality (composition)
82
Methods of imaging:
- computerized tomography (CT) - magnetic resonance imaging (MRI) - ultrasound
83
CT:
- x rays attenuated as they pass through tissues - different tissues = different density = different attenuation - regional values, whole body (limited)
84
Advantages of CT:
- greatest accuracy - high resolution, consistent values - measured comp of internal tissues and organs - detects regional shifts in body comp - instruments widely available
85
Limitations of CT:
- high cost, limited access - high radiation dose (repeated measures, special populations) - CT imaging research in body comp typically accesses stored images from medical records - requires technical skill - limited to subjects with BMI < 35
86
MRI:
- magnetic resonance imaging - generates a controlled magnetic field around the subject - number of hydrogen nuclei of tissues is measured - whole body and regional measurements
87
In MRI, tissues differ according to:
- number of hydrogen nuclei - relaxation time (time to release energy) - process repeated to map entire body - estimates tissue quantity and quality
88
MRI advantages:
- high accuracy - measured comp of internal tissues and organs - detects regional shifts in body comp - no radiation (repeated measures, most populations) - whole body and regional analysis
89
MRI limitations:
- high cost, limited access | - limited to subjects with BMI < 35
90
Advantages of ultrasound:
- non-invasive/safe - widely available - useful for longitudinal monitoring
91
Disadvantages of ultrasound:
- technical skill required/protocol | - sensitive to severe altered water balance
92
4 techniques of body comp and which body comp of interest for each:
- BIA (FFM) - DEXA (FFM, lean soft tissue, ASM) - ultrasonography (skeletal muscle) - CT (skeletal muscle)
93
Considerations of body comp:
- does it give you the info your client wants? - does it measure the compartment of interest? - $$, convenience, portable, frequency - subject status (age, health, fitness, compliance) - control of measurement variability
94
Variability in measurement could be due to:
- instrument error - investigator error - biological variability (activity, intake, etc.)
95
Why assess body comp?
- determine health status - monitor changes in body comp (growth, aging, disease) - evaluate efficacy of treatment (eg. exercise, diet, drug interventions designed to change body comp)
96
Skeletal muscle fundamental roles in human physiology:
- 40-50% of the body's mass - locomotion and movement - blood flow to organs - protection to vital organs - regulator of whole body metabolism (storage site/consumer of AA and glucose) (endocrine organ --> myokines)
97
Low muscle mass can be a predictor of:
- shorter survival - physical impairment/disability - greater length of hospital stay - need for rehab - post op complications - poor quality of life - tumor progression/toxicity