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HUNT242 > Lecture 3: Measuring Body Composition 2 > Flashcards

Lecture 3: Measuring Body Composition 2 Flashcards

1
Q

BMI calculation:

A

= weight (kg) / height (m2)

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2
Q

What are the advantages of measuring BMI?

A
  • easy, quick, non-invasive
  • correlates with percent body fat at group level
  • useful for individuals with additional information
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3
Q

What are the limitations from measuring BMI?

A
  • doesn’t tell you what weight is measuring
  • high BMI could be high lean, fat, oedema
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4
Q

What does a decrease in mid-upper-arm circumference reflect in high income countries?

A

Reduction in muscle or fat (or both)

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5
Q

What does a decrease in mid-upper-arm circumference reflect in low income countries?

A

Subcutaneous fat is low shows changes in muscle mass

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6
Q

What is Protein Energy Malnutrition (PEM)?

A

a condition caused by a severe deficiency of protein and calories, leading to a range of health problems including muscle wasting, stunted growth, and weakened immune function, commonly seen in developing countries

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7
Q

What muscle estimates can mid-upper-arm circumference show?

A
  • Mid-upper-arm muscle circumference (MUAMC)
  • Mid-upper-arm muscle area (AMA)
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8
Q

What are skinfolds?

A

Callipers measure fold of skin and underlying fat

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9
Q

How are skinfolds data used?

A
  • by comparing to percentiles
  • to calculate % fat using equations
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10
Q

What are common skinfold areas?

A
  • triceps
  • biceps
  • subscapular
  • suprailiac
  • thigh, calf, abdomen
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11
Q

What are the advantages of skinfolds?

A
  • simple
  • cheap
  • can be precise and accurate
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12
Q

What are limitations/assumptions made of skinfolds?

A
  • Constant skin and subcutaneous fat compressibility
  • Constant skin thickness
  • Chosen sit is good estimate of total fat
  • Subcutaneous fat represents constant proportion of total fat in every person
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13
Q

What is an oedema?

A

Oedema is the abnormal accumulation of extra-cellular fluid in tissues, causing swelling, often in the legs, feet, or hands

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14
Q

What is Dual-energy X-ray Absorptiometry (DEXA)?

A

Medical imagine technique - small amount of radiation used to measure lean mass, fat mass and bone mineral content

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15
Q

How does DEXA work (the principles)?

A
  • Dense tissues (e.g. bone) absorb more X-rays
  • Detectors measure intensity of X-rays passing through
  • W-dimensional image generated
  • Software algorithms calculate body composition
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16
Q

What are the advantages of DEXA?

A
  • accurate (2% error)
  • precise
  • suitable for almost all ages
  • Relatively quick
17
Q

What are the limitations of DEXA?

A
  • expensive
  • size limits
  • requires trained technician
18
Q

What are the 4 main types of approach for regional body composition?

A
  1. CT
  2. MRI
  3. DEXA
  4. Anthropometry
19
Q

What is computed tomography (CT)?

A

A rotating X-ray tube and detectors take detailed cross-sectional images that discriminate between visceral and subcutaneous fat

20
Q

What are CT’s used to measure?

A

Lean mass, fat mass and bone mineral content

21
Q

What are the advantages of CT’s?

A
  • “Gold standard”
  • Accurate
  • Measures visceral fat
22
Q

What are the limitations of CT’s?

A
  • Expensive
  • Higher levels of radiation than DXA
23
Q

What is magnetic resonance imaging (MRI)?

A

Strong magnetic field & radio waves take detailed cross-sectional images that discriminate between visceral and subcutaneous fat

24
Q

What are MRI’s used to measure?

A

Lean mass, fat mass and bone mineral content

25
Q

How do MRI’s work?

A

Different tissues emit different radio waves when H atoms aligned by magnetic field

26
Q

Which has better discrimination, MRI’s or CT’s?

A

MRI’s

27
Q

What are the advantages of MRI’s?

A
  • very accurate
  • no radiation!
  • measures visceral fat
28
Q

What are the limitations of MRI’s?

A
  • expensive
  • slow
  • strong magnetic field
29
Q

Can DEXA measure visceral fat?

A

From an automated image-processing algorithm using raw 2D images - cannot discriminate but can measure regions

30
Q

What is waist circumference a proxy for?

A

central fat

31
Q

What is hip circumference a proxy for?

A

peripheral fat

32
Q

Many now consider that waist circumference alone….

A

is a better indicator of visceral fat

33
Q

What are the advantages of anthropometry circumferences?

A

Simple

34
Q

What are the disadvantages of anthropometry circumferences?

A
  • Not direct measure of visceral fat
  • Difficult in very obese
35
Q

What percent body fat is considered normal?

A

Men: 15-22
Women: 18-32

36
Q

What percent body fat is considered overweight?

A

Men: >22
Women: >32

37
Q

What percent body fat is considered obese?

A

Men: >25
Women: >35

HUNT242 (24 decks)

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