NUTR 484 Lab Exam 2

fat free mass

everything besides adipose tissue
bones, muscles, nerves, etc.

Why measure fat free mass?

Health implications
Body weight recommendations
Describe populations

Why is all fat not bad?

Insulation
Protection
Myelination
Sex hormones
Neural development in infants, toddlers, and adolescents
High energy content (~9 kcals per gram of fat)

health ranges

Satisfactory ranges for health is 10-15% in men and 15-20% in females; Really 20-32% in females

why do females have more fat

Higher due to child development and pregnancy

Ways to determine body composition

Two compartment model (and a 3 and 5 compartment)
Field vs laboratory

Two compartment mode

Divides body to fat mass and fat free mass

Three compartment mode

fat mass, total body water, and fat free mass (dry)

more compartment mode

More components, more lab material you have to use

Field vs laboratory

DEXA scan
MRI
BIA
Bod Pod
Underwater weighing

DEXA scan

Dual energy x-ray absorptiometry
Does not require assumptions of biological constancies of fat and fat-free components
R=0.91 for women and R=0.92 for men

MRI

Magnetic resonance imaging
R = 0.84

BIA

Bioelectrical impedance analysis
Hydration status and location is measured
Cheapest
Fairly inaccurate
Don't really want to use these numbers for where you're at; can look at trend over time

Bod Pod

Air displacement plethysmography
R = 0.96 for one study
Pressurizes the chamber first and then person gets in
System analyzes volume and changes in pressure

underwater weighing

Lab technique where subjects are submerged into a large tank of water
Exhale as much air as they can
Scale stabilized

Archimedes principle

A body submerged in water will lose an amount of water equal to the weight of the water displaced
Using body density to determine body comp

Two component model

Fat component (fat weight, FW)
Fat free component
Should be between 0.90000 and 1.10000

fat component

Composed of adipose tissue and neural tissue
Density = 0.90000 g/mL or kg/L
Carry to 5 decimal places during calculations

fat free component

Bone, muscle, tendons, viscera, CT, etc
Density = 1.10000 g/mL

Residual volume

volume of air left in lungs after max expiration

VC

maximum volume of gas expelled from the lung voluntarily following a max inspiration

Air left in the gastrointestinal (GI) tract =

= 0.10L

Graph #1 UWW

Body density (Db) y
Body volume (BV) x
Negative linear
Shot put would sink (big density, small volume)
Basketball float (small density, big volume)
Dense sinks

Graph #2 UWW

UWW y
Body density (Db) x
Positive linear
Basketball toward 0 while shot put at top

Graph #3 UWW

% Fat y
Body Density (Db) x
Negative linear
More dense, less % fat
Basketball high %fat and low Db

Lab procedure UWW

Collect VC reading from bell spirometer
Multiple VC and BTPS correction factor
BTPS correction factor is based on spirometer air temp
Multiple corrected VCbtps by
VCbtps x 0.24 = RV for males
VCbtps x 0.28 = RV for females
Now predicted RV (residual volume)

True UWW

% fat -negative linear
Less UWW, more % fat

Greater density =

higher weight

Anthropometric Measurements

circumference, diameter, skinfolds, height, and weight

Field techniques for estimating body comp estimation; Advantages

Inexpensive
mobile
Time efficient

Field techniques for estimating body comp estimation; Disadvantages

Not as accurate
Error
~3-5% difference between UWW and skinfold

Circumferences

Measured in cm
Distance around a body part
Reflects fat weight (FW) and fat-free weight (FFW)
slightly gender dependent
Slightly site dependant

FFW

bone, muscle, skin

FW

adipose and nervous

Diameters

Measured in cm
Distance between 2 bony landmarks
Biacromial, biiliac, bitrochanteric

diameter measures

Reflect only FFW

skin folds

Measured in millimeters (mm)
Measures a fold of skin
Contains skin
Contains subcutaneous fat
Contains fascia (sometimes, but try not to)
Overestimates if too close, underestimate if too far

skin folds measure

only FW

Development of regression equations

Regression equations are statistical methods developed and used to relate 2 or more variables

Linear regression equation

form of a straight line y=m(x)+b

linear regression y

% fat

linear regression m

slope

linear regression x

Db^-1

linear regression b

y intercept

linear regression r

-0.95
Strong negative relationship between Db and % fat

Need to consider

population
actual body composition
Take a series of anthropometric measures
Determine most efficient measurements

define population

Who are we measuring?
Our purpose is NUTR 484; college aged males and females

Determine actual body composition

Use under water weight
Use gold standard first
Need to find exact

Take a series of anthropometric measures

Plug into equation
Take height, weight, age, abdominal, triceps, & thigh fold thickness

Determine most efficient measurements

Decide most efficient bases upon theory and practicality

theory

Females and males carry the most fat where?
Male and female fat deposition related to age, height, or weight?

Practically

How much time do you want to spend taking measurements?
Are they necessary?

Linear equations

Y = m(x)+b -> linear
Straight line

quadratic equations

Y = m(x1) +m(x2) + m(x2)^2 + b -> quadratic
Curved line; squared term causes this
Quadratic equations help bring extreme values closer to the prediction equation!

Criteria for choosing an equation

R value
Graph

R value

Goodness of fit
Evaluate standard error of estimate (SEE)
Represents the ERROR in new regression equation
Defines the error of the prediction equation by relating your predicted values to UWW values

Graph

% Fat UWW y
SF (thigh, hip, tricep, etc) x
Positive linear
Dots are % fat measures
Line is prediction equation

Calculating SEE

Find % Fat estimation for Db
((4.57 / 1.07970) - 4.142) *100 = 9.066%

upper bound

Db-0.00100 = x
((4.57 / x) - 4.142) *100 = 9.458%

lower bound

1.0797 + 0.001 = 0.08070
((4.57 / 1.08070) - 4.142) *100 = 8.674%

Sources of error of Anthropometric Measurements

Error from UWW
Inappropriate landmarks for anthropometric measures
Technique error

error from UWW

Assume that UWW is errorless -its not
Gold standard for finding body comp

Gold standard for finding body comp

Exercising or eating prior to UWW
Reading scale wrong
Subject’s level of comfort in/under water
Body water retention (medication, menstruation, etc)

Inappropriate landmarks for anthropometric measures

skin folds

skin folds inappropriate

Inappropriate landmarks
Equations based on anatomical landmarks contain error from landmarks that may/may not be representative
Sites need to be accurate and reliable
Sites measured multiple times on the same individual

Technique error

inter and intra tester error

Intra tester error

error within a tester, tester cannot take consistent measurements over time

inter tester error

error between testers, one tester may produce different results from the next tester

graph #1

Greater SF thickness (x), greater % fat UWW (y)

graph #2

Greater SF thickness (x), less Db UWW (y)

Subscapular fold

diagonal

triceps fold

vertical
Posterior midline of upper arm halfway between olecranon and acromion process
Elbow extended and relaxed

chest fold

diagonal

abdomen fold

vertical
Lateral distance 2 cm from umbilicus

supra iliac

diagonal
Top of iliac crest

thigh and medial calf

vertical
Midway of hip and knee

Females folds

triceps, thigh, and suprailiac

Medial calf fold

level of max circumference of the calf

Body build

Identifies distribution patterns of fat and lean tissues
Concerned with distribution
Cannot determine FW and FFW
Gives crude estimate of where its stored
Does take gender and age into account
Associated with health and performance
Use anthropometric measures for body build aspects
Predict success in certain sports

body build can not

determine FW and FFW

body build does

take in gender and age
give crude estimate of stored fat

Number of diseases associated with distributions of tissues

true

Predict success in certain sports

Mesomorph, ensomorph, ectomorph

Techniques for evaluation of body build

Behnke somatogram
Behnke method for reference weight
Heath-carter method of somatotyping

Behnke somatogram based on

Based on circumferences (cm)

Behnke somatogram shows

Graphic description of body proportions
General pattern of body mass distribution

Behnke somatogram tracks

disproportionate body segments
tracking growth and development in children

Behnke somatogram uses

Average circumference values (right and left circumferences added then divided by 2)

reflects fat

Chest, abs, hips, and thighs

If > 105% (fats)

less muscular

reflects muscle

Forearm, flexed arm, shoulder, and calf

If > 105% (muscles)

more muscular

bony sites

Wrist, knees, and ankles

< 95% bony sites

overweight; greater amount of tissue relative to skeletal size

> 105% bony sites

less tissue relative to skeletal size and so less fat

calculate

Get circumference measures of R and L limbs (when necessary)
Average limb circumference then work with average
(circumferences/constant) / total body: proportion score

Behnke method for reference weight

Average weight appropriate for particular frame size
Estimates ideal body weight based on skeletal size and height
Based on diameters of specific body sites (cm)

diameters measured where

across 2 bony landmarks
Add right and left (do not average)

Reference weight

Body weight - reference weight = +/- 5 kg = normal

BW-RW > 5kg

overweight