3: body composition Flashcards

Question

Reference Values for Waist Circumference/Waist-Hip ratio

Answer 1

o Waist circumference: – ≥ 102cm (40 inches) in men indicates increased risk – ≥ 88cm (35 inches) in women indicates increased risk o Waist-hip ratio = Waist girth (cm)/ Hip girth (cm)

Answer 2

Health Risks Men Women High >1.0 >0.85 Moderate 0.9-1.0. 0.80-0.85 Low <0.90 <0.80

Answer 3

o Measures body fat distribution and central obesity o Indicates risk of chronic disease o Monitor changes in circumferences associated with diet/PA interventions o Inexpensive, practical, widely used in combination with BMI o However, does not directly measure % body fat o Can be difficult to be accurate and consistent-will see this in the practical session. – Quite easy to ‘fool’ someone into thinking they have lost inches

Answer 4

o Measure of weight in relation of height o Kg/H^2 o Doesn’t directly measure &body fat or body fat distribution o Indicates risk of chronic disease

Answer 5

o 65% adults in Scotland are overweight, 26% obese

Answer 6

o Quantifies total body fat and fat free mass and in different parts of the body. o Means we can: – can get an accurate measure of % body fat – see where fat is distributed in the body

Answer 7

– Expensive (scanner is very expensive and costs ~£100 per measurement) – Trained professional required – Takes a lot of time – Small studies

Answer 8

– Highly accurate and consistent measure of body composition for research (Gold Standard) – Often used to validate (i.e. test accuracy) more practical measures of body composition

Answer 9

o Body fat is stored subcutaneously (under the skin) and can be measured using callipers o By measuring skin folds at various sites around the body it is possible to estimate % body fat – Commonly used to estimate % body fat and health risk. – The width of the skin fold is measured in millimetres with a specially calibrated calliper. – Each measurement is usually taken three times and then the average of the three measurements is recorded (accuracy). – The measurements from each site are entered into an equation, and body fat is calculated – All the skinfold equations estimate body density from the measurements which is then used to estimate percent body fat

Answer 10

o The more sites that are measured, the more accurate the body fatness estimate o Most common measurement sites are: – Triceps, subscapular, suprailiac, abdomen and upper thigh o Various equations and several sites can be used to estimate % body fat.

Answer 11

– Practical, relatively cheap – Can be used in all populations – Can provide reasonably accurate and consistent estimates of % body fat IF the technician is highly skilled

Answer 12

– Can be difficult to locate the correct sites, to measure the skin folds accurately, esp obese people (as the thickness of the skinfold might exceed the width of the calliper or might not grasp the whole fold of skin) and in those with very little body fat (difficult to grasp a fold of skin to measure). – Can be difficult to measure skinfold thicknesses consistently, need to be able to locate the exact same sites each time and measure the skin folds the exact same way. – To obtain accurate and consistent SFM, requires lots of training and practice (i.e. practice on ~50 people)

Answer 13

o Electrodes (source and detector) are placed on the body o A small, painless electrical current is introduced o Current will flow more rapidly through body water and lean tissue; fat tissue will impede the current o This is because lean tissue contains more electrolytes, whereas fat contains only small amounts of water (and electrolytes) o BIA measures impedance to electrical current flow between the source and detector electrodes o The impedance value is used in an equation to calculate % body fat, FM, FFM

Answer 14

– Safe and relatively easy to use – Can provide reasonably accurate and consistent estimates of % body fat IF correct procedures have been followed

Answer 15

– Tends to overestimate body fatness in lean people and underestimate in obese people – Correct placement of electrodes & body position to improve accuracy – Hydration level and skin temperature can affect the estimate of % body fat.

Answer 16

o Several methods to measure body composition each o with its own benefits and drawbacks. o When selecting the best method to measure body composition we need to consider: – How accurately do we need to assess body composition? – How reliable (consistent) do you need the method to be? – How much can you afford to spend? – Skill of the investigator/practitioner – Comfort of the subject