Lab 7: Body Composition

Question 1

what can information derived from body composition be useful for?

Answer 1

risk assessment, individualization of exercise prescriptions, and evaluating interventional progress

Question 2

what is anthropometry?

Answer 2

measurement of the body (weight, height, and waist circumference)

Question 3

how is body mass index (BMI) calculated?

Answer 3

weight (kg) divided by height (m^2)

Question 4

why is BMI not an adequate measurement of disease risk for some individuals? which individuals might this be an issue for?

Answer 4

there is no way to determine the composition of the weight (fat vs. muscle); weight-training individuals

Question 5

what is waist circumference a valuable measurement for?

Answer 5

to assess central obesity

Question 6

what is fat located in the abdominal region associated with (as compared to peripheral fat)? can it predict risk without a marked increase in BMI?

Answer 6

greater health risk; independent risk-predictor when BMI is not markedly increased

Question 7

why is waist circumference utilized in addition to BMI?

Answer 7

because it measures abdominal obesity and fat distribution; it can also be used to monitor the efficacy of weight-loss programs

Question 8

what do generalizable equations account for? what equation will we use?

Answer 8

differences in age, gender, race and ethnicity; Siri equation to predict percent body fat

Question 9

skinfold measurements are an example of what type of body composition measurement method? what are the equations based on?

Answer 9

doubly indirect; equations based on hydrostatic weighing (water displacement to estimate fat mass)

Question 10

2 assumptions of skinfold measurements

Answer 10

1) subcutaneous fat is directly proportional to total fat
2) the skinfold sites selected are representative of total body subcutaneous fat

Question 11

what affects the proportion of subcutaneous to total body fat?

Answer 11

age, sex, race and ethnicity etc.

Question 12

limitations of the skinfold analysis technique

Answer 12

technician training, applicability of equations to the individual being tested, skinfold site measurement accuracy, and measurement technique

Question 13

SEE of the skinfold analysis technique

Answer 13

3.5%

Question 14

what is the bioelectrical impedance analysis (BIA) technique based on?

Answer 14

based on the principle that electrical current flows at different rates through the body depending upon its composition; body fat provides more resistance to electrical flow than fat-free mass and slows the rate at which the current travels

Question 15

how does the DEXA system measure body composition?

Answer 15

utilizes X-rays to scan and differentiate body weight into 3 components: lean soft tissue, fat soft tissue, and bone

Question 16

why is the percentage body fat significantly higher for DEXA than anthropometric results?

Answer 16

because the DEXA can measure not only subcutaneous fat, but also visceral, retroperitoneal, and intramuscular fat as well

Question 17

what will the T score compare?

Answer 17

compares your bone density to the average bone density of young healthy adults of the same sex

Question 18

what will the Z score compare?

Answer 18

compares your bone density to the average bone density of someone your same age, sex, and race/ethnicity

Question 19

are there any accepted standards for percent body fat? what about BMI and waist circumference?

Answer 19

no, all methods for percent body fat are indirect and involve error; there are national standards for BMI and waist circumference though

Question 20

what does accuracy represent?

Answer 20

how close a measured value is to the true value

Question 21

what does precision represent?

Answer 21

how close measured values are to each other

Question 22

what does bias represent?

Answer 22

whether there are systematic differences between measured and true values

Question 23

3 components of the athlete triad

Answer 23

1) low energy availability (with or without disordered eating)
2) functional hypothalamic amenorrhea (females) or hypogonadotropic hypogonadism (males)
3) osteoporosis

Question 24

what is energy availability defined by?

Answer 24

(dietary intake - exercise energy expenditure) / fat free mass (kcal/kg)

Question 25

if an athlete with a FFM of 60 kg consumes 3000 kcal per day and has an exercise energy expenditure of 600 kcal per day, what is their energy availability (EA)?

Answer 25

[(3000 kcal - 600 kcal)/60 kg FFM] = 40 kcal/kg

Question 26

what EA value is associated with deleterious effects?

Answer 26

less than 30 kcal/kg

Question 27

underweight BMI (kg/m^2)

Answer 27

<18.5 kg/m^2

Question 28

normal BMI

Answer 28

18.5-24.9 kg/m^2

Question 29

overweight BMI

Answer 29

25.0 - 29.9 kg/m^2

Question 30

obesity class I BMI

Answer 30

30.0-34.9 kg/m^2

Question 31

obesity class II BMI

Answer 31

35.0-39.9 kg/m^2

Question 32

extreme obesity (obesity class III) BMI

Answer 32

> 40.0 kg/m^2

Question 33

bone density within 1 SD of the young adult mean is considered

Answer 33

normal

Question 34

bone density between 1 and 2.5 SD below the young adult mean is considered

Answer 34

low bone mass

Question 35

bone density 2.5 or more SD below the young adult mean is considered to be

Answer 35

osteoporosis

Question 36

bone density more than 2.5 below the SD of the young adult mean accompanied by one or more osteoporotic fractures is considered to be

Answer 36

severe (established) osteoporosis

Question 37

describe the procedure generally

Answer 37

1) every student has DEXA already, every student will perform and receive skinfold measurements, and every student will receive BIA measurements
2) separate into two groups: males and females
3) perform anthropometric measurements (including weight, height, waist circumference, and skinfold measurements)

Question 38

examples of direct body composition measurements

Answer 38

chemical analysis of a cadaver

Question 39

examples of indirect methods of body composition measurement (derived from from direct methods)

Answer 39

DEXA

Question 40

examples of doubly indirect methods of body composition measurement (derived from indirect methods)

Answer 40

skinfold measurements and BIA