Lab 7: Body Composition Flashcards
what can information derived from body composition be useful for?
risk assessment, individualization of exercise prescriptions, and evaluating interventional progress
what is anthropometry?
measurement of the body (weight, height, and waist circumference)
how is body mass index (BMI) calculated?
weight (kg) divided by height (m^2)
why is BMI not an adequate measurement of disease risk for some individuals? which individuals might this be an issue for?
there is no way to determine the composition of the weight (fat vs. muscle); weight-training individuals
what is waist circumference a valuable measurement for?
to assess central obesity
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?
greater health risk; independent risk-predictor when BMI is not markedly increased
why is waist circumference utilized in addition to BMI?
because it measures abdominal obesity and fat distribution; it can also be used to monitor the efficacy of weight-loss programs
what do generalizable equations account for? what equation will we use?
differences in age, gender, race and ethnicity; Siri equation to predict percent body fat
skinfold measurements are an example of what type of body composition measurement method? what are the equations based on?
doubly indirect; equations based on hydrostatic weighing (water displacement to estimate fat mass)
2 assumptions of skinfold measurements
1) subcutaneous fat is directly proportional to total fat
2) the skinfold sites selected are representative of total body subcutaneous fat
what affects the proportion of subcutaneous to total body fat?
age, sex, race and ethnicity etc.
limitations of the skinfold analysis technique
technician training, applicability of equations to the individual being tested, skinfold site measurement accuracy, and measurement technique
SEE of the skinfold analysis technique
3.5%
what is the bioelectrical impedance analysis (BIA) technique based on?
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
how does the DEXA system measure body composition?
utilizes X-rays to scan and differentiate body weight into 3 components: lean soft tissue, fat soft tissue, and bone
why is the percentage body fat significantly higher for DEXA than anthropometric results?
because the DEXA can measure not only subcutaneous fat, but also visceral, retroperitoneal, and intramuscular fat as well
what will the T score compare?
compares your bone density to the average bone density of young healthy adults of the same sex
what will the Z score compare?
compares your bone density to the average bone density of someone your same age, sex, and race/ethnicity
are there any accepted standards for percent body fat? what about BMI and waist circumference?
no, all methods for percent body fat are indirect and involve error; there are national standards for BMI and waist circumference though
what does accuracy represent?
how close a measured value is to the true value
what does precision represent?
how close measured values are to each other
what does bias represent?
whether there are systematic differences between measured and true values
3 components of the athlete triad
1) low energy availability (with or without disordered eating)
2) functional hypothalamic amenorrhea (females) or hypogonadotropic hypogonadism (males)
3) osteoporosis
what is energy availability defined by?
(dietary intake - exercise energy expenditure) / fat free mass (kcal/kg)
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)?
[(3000 kcal - 600 kcal)/60 kg FFM] = 40 kcal/kg
what EA value is associated with deleterious effects?
less than 30 kcal/kg
underweight BMI (kg/m^2)
<18.5 kg/m^2
normal BMI
18.5-24.9 kg/m^2
overweight BMI
25.0 - 29.9 kg/m^2
obesity class I BMI
30.0-34.9 kg/m^2
obesity class II BMI
35.0-39.9 kg/m^2
extreme obesity (obesity class III) BMI
> 40.0 kg/m^2
bone density within 1 SD of the young adult mean is considered
normal
bone density between 1 and 2.5 SD below the young adult mean is considered
low bone mass
bone density 2.5 or more SD below the young adult mean is considered to be
osteoporosis
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
severe (established) osteoporosis
describe the procedure generally
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)
examples of direct body composition measurements
chemical analysis of a cadaver
examples of indirect methods of body composition measurement (derived from from direct methods)
DEXA
examples of doubly indirect methods of body composition measurement (derived from indirect methods)
skinfold measurements and BIA
