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HUNT242 > Lecture 2: Measuring Body Composition 1 > Flashcards

Lecture 2: Measuring Body Composition 1 Flashcards

1
Q

What is the two-component model?

A

Fat mass (FM) + fat-free mass (FFM)

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2
Q

What does the two-component model assume?

A

Assumes the total body mass is composed of two components and the densities of each component are known and the same for all individuals (E.g. FFM is constant)

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3
Q

What is the three-component model?

A

Fat mass (FM) + (Bone mineral content + Bone-free fat-free mass)

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4
Q

What is bone-free fat-free mass?

A

Lean tissue mass

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5
Q

Why do we measure body composition?

A
  • Health
  • Sports performance
  • Monitoring growth
  • Assessing response to intervention
  • Creation of reference values
  • Population monitoring
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6
Q

High body fat in the ?? area is associated with increased health risks

A

Abdominal

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7
Q

How do we measure fat % of total body composition?

A

%fat = (FM / body weight) x 100

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8
Q

How do we measure free fat mass (FFM) % of total body composition?

A

%FFM = (FFM / body weight) x 100

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9
Q

What is regional body composition?

A

Whether fat is stored primarily in the central or peripheral regions

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10
Q

Health risks of obesity depend on ??? as well as total body composition

A

Regional fat distribution

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11
Q

What is a android fat distribution?

A

Central = Fat accumulation in the abdominal area, leading to an “apple-shaped” body

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12
Q

What is gynoid fat distribution?

A

Peripheral = fat is stored in the hips, thighs, and buttocks leading to a “pear-shaped” body

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13
Q

What type of fat is android distribution? (Central)

A

Visceral fat - stored deep within the abdominal cavity around vital organs like the liver, pancreas, and intestines.

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14
Q

What type of fat is gynoid distribution? (Peripheral)

A

primarily subcutaneous fat (stored under the skin)

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15
Q

Why is central worse than peripheral?

A
  • metabolically active
  • contributes to chronic inflammation
  • increases risk of heart disease and diabetes
  • impacts organ function.
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16
Q

What shape do women tend to be?

A

More gynoid (peripheral)

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17
Q

What health risks does central adiposity increase?

A
  • T2D
  • CHD
  • CVD
  • Arthritis
  • Hypertension
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18
Q

What is central fat composed of? (Equation)

A

Central fat = visceral (intra-abdominal) and subcutaneous (under the skin) fat

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19
Q

What are some ways to measure total body composition? (2 component model)

A
  • Underwater weighing
  • Air displacement plethysmography
  • BIA
  • Anthropometry
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20
Q

What are some ways to measure regional body composition?

A
  • CT
  • MRI
  • DXA
21
Q

What are the three main types of approach for the two-component model?

A
  • Densitometry
  • Electrical resistance of the body
  • External measurement
22
Q

What are examples of measuring densitometry?

A
  1. Underwater weighing
  2. Air displacement plethysmography
23
Q

What is an example of measuring electrical resistance of the body?

A

Bioelectrical impedance analysis (BIA)

24
Q

What is an example of taking an external measurement?

A

Anthropometry

25
Q

What is the equation for density?

A

mass/volume

26
Q

What is the main densitometry equation used to calculate %fat from total body density?

A

Siri:
%Fat = ((4.950/D) - 4.500) x 100%

27
Q

What are assumptions that are made when using densitometry?

A
  • Density of FFM is constant
  • Density of Fat does not vary
  • Water content of FFM is constant
  • Proportion of bone to FFM is constant
28
Q

What is underwater weighing?

A

measuring a person’s body density based on their weight underwater compared to their weight on land

29
Q

What are the advantages to underwater weighing?

A
  • “gold standard”
  • Accurate
  • 2% error
30
Q

What are the limitations to underwater weighing?

A
  • density of FFM not necessarily uniform
  • do 4-12 times
  • not suitable for all
  • breathing apparatus to measure lung volume
  • bulky equipment
31
Q

What is air displacement plethysmography?

A

Similar principle to underwater weighing except calculate displaced air rather than displaced water

32
Q

What is bioelectrical impedance analysis (BIA)?

A

Body conducts electricity through FFM - pass weak current through body and measure impedance to current

33
Q

What is impedance?

A

Converts (resistance + reactance) to estimate FFM

34
Q

How is BIA calculated?

A
  1. FFM predicted from TBW estimates
  2. FM then derived as difference between body weight and FFM
35
Q

What percent of FFM is water?

A

approx. 73%

36
Q

What can the validity of BIA be impacted by?

A
  • hydration status
  • recent PA
  • food consumption
  • menstrual status
  • body position
37
Q

What is good practice for BIA?

A
  • avoid alcohol & vigorous exercise 24-48 hours before
  • measure >2h after eating and within 30 min of voiding
  • lie down with limbs not touching body
38
Q

How do you improve the measurement of BIA?

A

By adding sex and age

39
Q

What are the advantages of BIA?

A
  • simple
  • cheap
  • portable
  • suitable for all ages
40
Q

What are the limitations of BIA?

A
  • need to be fasting
  • control recent activity & hydration status
  • need appropriate equation
41
Q

What is the most widely used method of measurement?

A

Anthropometry

42
Q

What does anthropometry involve?

A

BMI, skinfolds, circumferences, breadths

43
Q

How do we interpret anthropometry measurements?

A
  • compare results with reference data
  • using cut offs that relate to risk
44
Q

What does anthropometric reference data need to be?

A
  • developed from group representative of healthy population
  • need to be specific (age, gender, ethnicity)
45
Q

What are percentiles?

A

Describe the position of the measurements in relation to the measurements for a population

46
Q

What are the advantages to anthropometry?

A
  • simple
  • safe
  • noninvasive
  • cheap
  • portable equipment
  • commonly used for large studies
47
Q

What are the limitations to anthropometry?

A
  • less accurate so less sensitive to change
48
Q

What are potential sources of error for anthropometry?

A
  • measurement error
  • variation in tissue composition
  • assumptions may not be valid in disease states or obesity

HUNT242 (24 decks)

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