Lecture 3: Measuring Body Composition 2 Flashcards
(37 cards)
BMI calculation:
= weight (kg) / height (m2)
What are the advantages of measuring BMI?
- easy, quick, non-invasive
- correlates with percent body fat at group level
- useful for individuals with additional information
What are the limitations from measuring BMI?
- doesn’t tell you what weight is measuring
- high BMI could be high lean, fat, oedema
What does a decrease in mid-upper-arm circumference reflect in high income countries?
Reduction in muscle or fat (or both)
What does a decrease in mid-upper-arm circumference reflect in low income countries?
Subcutaneous fat is low shows changes in muscle mass
What is Protein Energy Malnutrition (PEM)?
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
What muscle estimates can mid-upper-arm circumference show?
- Mid-upper-arm muscle circumference (MUAMC)
- Mid-upper-arm muscle area (AMA)
What are skinfolds?
Callipers measure fold of skin and underlying fat
How are skinfolds data used?
- by comparing to percentiles
- to calculate % fat using equations
What are common skinfold areas?
- triceps
- biceps
- subscapular
- suprailiac
- thigh, calf, abdomen
What are the advantages of skinfolds?
- simple
- cheap
- can be precise and accurate
What are limitations/assumptions made of skinfolds?
- 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
What is an oedema?
Oedema is the abnormal accumulation of extra-cellular fluid in tissues, causing swelling, often in the legs, feet, or hands
What is Dual-energy X-ray Absorptiometry (DEXA)?
Medical imagine technique - small amount of radiation used to measure lean mass, fat mass and bone mineral content
How does DEXA work (the principles)?
- 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
What are the advantages of DEXA?
- accurate (2% error)
- precise
- suitable for almost all ages
- Relatively quick
What are the limitations of DEXA?
- expensive
- size limits
- requires trained technician
What are the 4 main types of approach for regional body composition?
- CT
- MRI
- DEXA
- Anthropometry
What is computed tomography (CT)?
A rotating X-ray tube and detectors take detailed cross-sectional images that discriminate between visceral and subcutaneous fat
What are CT’s used to measure?
Lean mass, fat mass and bone mineral content
What are the advantages of CT’s?
- “Gold standard”
- Accurate
- Measures visceral fat
What are the limitations of CT’s?
- Expensive
- Higher levels of radiation than DXA
What is magnetic resonance imaging (MRI)?
Strong magnetic field & radio waves take detailed cross-sectional images that discriminate between visceral and subcutaneous fat
What are MRI’s used to measure?
Lean mass, fat mass and bone mineral content
