Lecture 9 - Measurement of body composition Flashcards
- main storage form of energy in the body
Body fat
- sensitive to acute malnutrition
body fat
- provides indirect estimates of changes in energy balance
body fat
- most variable component of the body
body fat
how is body fat the most variable component of the body? (3)
- differing among individuals of the same sex, height, and weight
- essential fat is found on the bone marrow, CNS, and mammary glands
- storage fat is found in the inter- and intra-muscular tissues, those surrounding the gastrointestinal tract and other organs and subcutaneous fat
why do we measure body fat?
to assess undernutrition and overnutrition as well as to determine the amount of body fat and its distribution in the body
Methods of estimating body fat - Common measurements
- skin fold thickness
- body mass index
- waist circumference
- waist-to-hip circumference ratio
Newer techniques - direct, more expensive of Methods of estimating body fat
- Ultrasound
- Computed tomography (CT) Scan
- Magnetic resonance imaging (MRI)
- Provides an estimate of the size of the subcutaneous fat depot which in turn provides an estimate of the total body fat
- Most widely used method of indirectly estimating percent body fat
Skinfold thickness
What does skinfold thickness assume? (2)
- assumes that (1) thickness of subcutaneous adipose tissue reflect a constant proportion of their total body fat and (2) skinfold sites selected for measurement either singly or in combination represent the thickness of the entire subcutaneous tissue
Advantages of using skinfold thickness measurement
- Equipment needed is inexpensive and
requires little space. - Measurements are easily and quickly
obtained. - When correctly done, measurements provide
estimates of body composition that correlate
well with those from hydrostatic weighing.
Instruments for skinfold thickness measurement
- use of precision calipers
- Lange caliper
- Harpenden caliper
- Holtain caliper
give smaller skinfold thickness values
both the Harpenden and Holtain caliper
fitted with a lighter spring
Lange caliper
Where do the calipers come from?
- Lange caliper - US
- Harpenden and Holtain - Great Britain and Europe
What caliper did the MGRS which produced the WHO child growth standards use?
Harpenden caliper
Skinfold thickness sites
- most used are the tricep, subscapula, and suprailiac skinfolds
- measured at the midpoint of the back of the upper arm
Triceps skinfold thickness measurement
- measured below and laterally to the angle of the left shoulder blade with the shoulder and arm relaxed
Subscapular skinfold thickness measurement
- measured in the mid auxiliary line immediately superior to the iliac breast
Suprailiac skinfold thickness measurement
Limitations of using a single skinfold thickness measurement (3)
- Large inter-individual differences exist in fat distribution
- 2. As total body fat changes, each skinfold site responds differently
- 3. Relationship between skinfold thickness and total body fat is complex
- Large inter-individual differences exist in fat distribution
- provides the most useful population-level measure of obesity
BMI
defined as the excessive fat or abnormal fat accumulation in the adipose tissues to the extent that health may be impaired
OBESITY
- used to estimate prevalence of obesity and the risk associated with it
- correlates with the amount of body fat but it does not directly measure body fat
- not a real measure of obesity but we do not have any other tool
BMI