Section 7 - Body Composition

Question 1

What are the two key sex based differences in body composition?

Answer 1

1. Females have more fat mass as a percentage of their total mass
2. The distribution of fat mass is different between males and females

Question 2

What is another name for Body Mass Index (BMI)?

Answer 2

Quetelet’s Index; because Jacques Quetelet came up with this measurement

Question 3

What are some major limitations to BMI?

Answer 3

1. Holds muscle, fat bone, vital organs as all equal
2. Doesn’t account for ethnic differences in BF%
3. Doesn’t account for age related increases in BF%

Question 4

How does Waist Circumference relate to Body Composition Assessment?

Answer 4

• Waist Circumference (WC) is a simple but meaningful measure of body composition health and predictor of chronic disease risk
• A larger WC value means greater amount of fat throughout one’s abdomen

Question 5

What are the cutoffs for Waist Circumference?

Answer 5

Healthy WC cutoffs: <80cm for females and <94cm for males

Considered to have abdominal obesity if above 88cm for females and 102cm for males

Males have higher thresholds because they deposit more fat naturally in their abdomen so there is more room for allowance for that

Question 6

How do Skinfolds relate to Body Composition Assessment? What are some points to consider when doing this kind of assessment?

Answer 6

Skinfolds measure the thickness of fat-folds including the skin at various sites around the body

Skinfolds can give us a direct idea of how much body fat resides in the area we are testing

Points to consider:

1. Only subcutaneous fat is measured
2. The sum of skinfolds does provide a direct assessment of fat loss or gain
3. Provides fairly accurate prediction of BF%

Question 7

How do DXA scans relate to Body Composition Assessments?

Answer 7

DXA scans are the most popular and used easily by an exercise professional

Benefits to using DXA scans:

1. Provides excellent assessment of lean body mass and fat mass
2. Gives us bone density
3. Available at an economical price and quick to do
4. Worries of radiation exposure are unfounded
5. Minimally invasive

Question 8

How do MRIs relate to Body Composition Assessment?

Answer 8

MRIs are more sensitive than DXA scans because MRIs can determine how much fat is in organs and other tissues that have fat droplets

MRIs are powerful but are not used very often to determine body fat and are used as a research tool primarily

Question 9

What are the three main goals/approaches for Body Composition fitness?

Answer 9

1. Work with a client to find a healthy proportion of fat mass to lean body mass
2. Work with obese clients to reduce overall mass to improve BMI to a healthier category
3. Work with athletes to maintain, increase, or decrease mass for sports performance in a healthy way

Question 10

The average client has the primary goal of losing body fat, to do that we need to place the client in a negative energy balance. How do we create that negative balance?

Answer 10

Calories OUT need to exceed calories IN. We can do this by:

1. Increase energy expenditure and maintain energy intake
2. Decrease energy intake and maintain energy expenditure
3. Most aggressive way: reduce energy intake and increase energy expenditure

Question 11

What are some indirect benefits that PA and Exercise can have on Body Composition?

Answer 11

1. Exercise suppresses appetite - which influences energy intake behaviours
2. You add more EE in the recovery phase of the exercise which increases your RMR
3. When you reduce EI, you lose both fat and muscle mass - if you go on a diet and do lots of activity then your body loses primarily fat mass