3: body composition

Question 1

o Body composition and what does it make up

Answer 1

relative amounts (or %) of tissue types in the body

a person’s body mass (weight)

Question 2

different tissue types that make up the body

Answer 2

including lean tissues (muscle, bone, and organs) and adipose tissue (fat)

Question 3

What is Fat Free Mass (FFM)

Answer 3

lean tissues

Question 4

o Body mass is generally divided into

Answer 4

Fat Mass (FM) and Fat Free Mass

Question 5

o % body fat =

Answer 5

Fat mass expressed as a percentage of total body mass

Question 6

Two Fat Tissues Types:

Answer 6

Essential and Non-essential Fat

Question 7

(Essential fat)

Answer 7

o The body requires a certain amount of body fat to function. Not all fat is bad for us

Crucial for normal physiological functions

Question 8

sex-specific essential fat required in female is for

Answer 8

normal hormonal functions (e.g. childbearing)

Question 9

fat stored in addition to sex-specific essential fat

Answer 9

non-essential fat or storage fat

Question 10

o Nonessential fat is

Answer 10

extra fat stored in the body
– Mainly located in fat cells or adipose tissue
– Factors such as gender, diet and exercise influence the amount of nonessential fat.

Question 11

Visceral fat location

Answer 11

inner abdominal organs (e.g. stomach and liver).

Question 12

visceral fat causes:

Answer 12

– heart disease
– Insulin resistance
– diabetes (visceral fat is suspected to be the biggest factor in the development of insulin resistance).

Question 13

o Decreasing visceral fat can dramatically lower;

Answer 13

– blood pressure,
– provide more favourable cholesterol levels
– Insulin resistance

Question 14

o Visceral fat is highly responsive to

Answer 14

diet and exercise.

Question 15

Levels of Body Fat amongst Athletes

Answer 15

o In sports which require muscular power
large body mass, with average-low levels of body fat

Question 16

Essential and Storage Fat men

Answer 16

15% body fat
– 12% storage fat
– 3% essential fat

Question 17

Essential and Storage Fat women

Answer 17

27% body fat
15% storage fat
12% essential fat

Question 18

Recommended levels of body fatness for health

Answer 18

10% - 22% men
20% -32% women

– Used to interpret body fat results BUT ranges may differ by age, sex, and ethnicity

o Too little body fat may be harmful to health.
o Too much can also be harmful to health

Question 19

Overfat: Health Problems

Answer 19

o Having too much body fat may lead to:
– Coronary heart disease
– Hypertension
– Hypercholesterolemia
– Diabetes
– Poor psychological health

o These can lead to premature death

Question 20

Levels of Body Fat amongst Athletes

Answer 20

o In weight-bearing, endurance activities
– Athletes have low body mass and minimal levels of body fat (e.g. distance runners ~5% BF for men and ~10 BF for women)
– This physique is an advantage in weight bearing endurance events

Question 21

Measurement of body composition

Answer 21

o There are many ways to assess body composition and they vary in practicality and accuracy.
– Dual-energy X-ray absorptiometry (DXA)
– Underwater weighing
– Bioelectrical Impedance (BIA)
– Ultrasound
– Infra-red sensors
– Skin fold measurements
– Waist circumference or waist to hip ratio (WHR)
– Body mass index (BMI)

Question 22

o Fat stored in upper body –

Answer 22

“apple” shaped

Question 23

o Fat stored in lower body –

Answer 23

“pear” shaped

Question 24

Waist circumference/Waist-Hip ratio

Answer 24

o Used as indicators of body fat distribution, central obesity, and risk of cardiovascular diseases and type 2 diabetes

Question 25

Reference Values for Waist Circumference/Waist-Hip ratio

Answer 25

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)

Question 26

Reference Values for Waist Circumference/Waist-Hip ratio

Answer 26

Health Risks Men Women

High >1.0 >0.85
Moderate 0.9-1.0. 0.80-0.85
Low <0.90 <0.80

Question 27

Waist circumference/WHR

Answer 27

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

Question 28

Measuring Body Weight and Changes in Body Weight (and BMI)

Answer 28

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

Question 29

Prevalence of Overweight and Obesity in Scotland (Scottish Health Survey 2017)

Answer 29

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

Question 30

Dual-energy X-ray absorptiometry (DXA)

Answer 30

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

Question 31

DXA weaknesses

Answer 31

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

Question 31

DXA strengths

Answer 31

– 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

Question 32

skin fold measurments

Answer 32

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

Question 33

skin fold sites

Answer 33

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.

Question 34

Skin fold Measurements Strengths

Answer 34

– 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

Question 35

skin fold measurements weaknesses

Answer 35

– 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)

Question 36

Bioelectrical Impedance Analysis (BIA) procedure

Answer 36

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

Question 37

Bioelectric Impedance Analysis Strengths

Answer 37

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

Question 38

Bioelectric Impedance Analysis Weaknesses

Answer 38

– 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.

Question 39

considerations of BIA

Answer 39

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