NUT 112: Lab 1
Student name:
2014
Lab TA: ____________________________________
Lab Exercise 3
Body Composition Assessment
(164 points)
Introduction
With the rising prevalence of overweight and obesity, there is increasing interest in the understanding of body
composition, particularly the body fat compartment. Obesity, or excessive body fat content, is associated with
increased risk of several chronic diseases (e.g., coronary artery disease, hypertension, type II diabetes) and
diminished longevity. Measurement of body density by hydrostatic weighing is generally considered the
reference technique for evaluating other methods of measuring body composition. However, this test requires
the use of special facilities (for underwater weighing) or expensive equipment (for air displacement
plethysmography). Thus, simple techniques are needed to assess the presence of obesity and to detect changes
in response to therapy. During this lab exercise, you will:
1. gain practical experience in measuring skinfold thickness at different anatomical sites, mid-upper arm
circumference, waist circumference, and hip circumference
2. use these measured values to calculate body mass index, arm muscle area, arm fat area, waist-to-hip
ratio, and compare these results with reference data or cutoff values for US adults
3. estimate body composition (% body fat mass) by using two techniques (bioelectrical impedance
spectroscopy and skinfold thickness) and to compare these results with the body mass index.
Section 1: Measurements
1) Work together with a lab partner or small group to measure the following indicators. You must be able to
successfully demonstrate each measurement to your TA during this lab section. Use the instructions provided in
the lab appendix and the information provided by your TA during the beginning of your lab section to help you.
We encourage you to record your own values in the separate Personal Data Sheet, though you are not required to
submit this sheet for grading. Each of these measurements requires practice on a number of different subjects to
perform the measurements accurately and precisely. Skinfold measurements can be particularly challenging, so
it is worth practicing on a variety of different people. After practicing the measurements a few times with your
lab partner or small group, you must demonstrate each measurement to your TA. Once you have demonstrated
proper technique for each measurement, the TA will sign their initials in Table 1. (70 points)
1
NUT 112: Lab 1
2014
Student name:
Lab TA: ____________________________________
Table 1: Anthropometric measurement indicators
Measurement
TA initials
Mid-upper arm circumference
Triceps skinfold thickness
Biceps skinfold thickness
Suprailiac skinfold thickness
Subscapular skinfold thickness
Waist circumference
Hip circumference
2. It takes a great deal of supervised training to become proficient at obtaining these anthropometric
assessments. Now that you have measured skinfold thicknesses, waist, hip, and arm circumferences as well
as height and weight (during last week’s lab), what did you find most challenging about taking these
measures? (2 points)
3. Measurement of % body fat by bioimpedance analysis (BIA)
For this part of the lab assignment, we will use bioelectrical impedance analysis and single frequency
bioimpedance to measure the total body water of at least one member out of each group of 4-6 students.
The results are affected by hydration status, physical exercise, and recent consumption of food, liquids and
alcohol, so students should report for measurements after at least 30 minutes of rest following cycling or other
exercise. Ideally, students should consume their previous meal at least two hours before the measurement. For
this procedure, the subject’s body mass (weight) and height are recorded (as obtained during the previous lab).
The subject then lies on the examining table in the supine position. The assistant will attach electrodes to one
wrist and ankle and a current will be passed through the body from one set of electrodes to the other (this
procedure is completely painless!). Using the information on the subject’s sex, body weight and height, and
measured resistance between the wrist and ankle, the computer will calculate the subject’s total body water, fat
mass, and fat-free mass.
We encourage you to have yourself measured using the BIA machine during your lab section. However, it is
not required for every student to participate. However, each small group of 4-5 students should have one
volunteer who is willing to have themselves measured. After you have participated in and/or observed at least
one measurement, the TA will initial below. (10 points)
Measurement
Bioelectrical impedance analysis
2
TA initials
NUT 112: Lab 1
2014
Student name:
Lab TA: ____________________________________
Section 2: Problem set
1. For each of the six subjects below, calculate their BMI and indicate which classification they fall in. Use
Table A1 in the Appendix to determine the appropriate classification for each subject. For measurements
recorded inches or pounds, convert values to meters and kilograms. (Note: 2.2lb = 1 kg; 1 inch = 0.0254 m; 1
cm = 0.01 m). (20 points)
*Ray, Caucasian male, 65 y/o, 187 cm, 182 lb
Joe, African American male, 21 y/o, 5’11”, 122 lb
Saul, Mexican American, 41 y/o, 5’9”, 195 lb
Subject
*Ray
Weight (kg)
82.7
Height (m)
1.87
Tanya, African American female, 26 y/p, 5’2”, 96 lb
Sara, Caucasian female, 53 y/o, 5’4”, 185 lb
Maria, Mexican American female, 31 y/o, 170 cm, 60.8 kg
BMI (kg/m2)
23.6
Classification
Normal Range
Sara
Joe
Saul
Tanya
Maria
2. Interpretation of skinfold thickness
The use of skinfold measurements to estimate body composition is based on the assumption that the sum of
subcutaneous fat stores at selected sites is representative of all subcutaneous fat and that there is a strong
relationship between subcutaneous fat and total body fat. Neither of these assumptions is completely true, but
the relationships are sufficiently strong that measurement of skinfold thickness at specific sites can be used with
a reasonable degree of confidence to estimate total body fat. In this section of today's lab, you will use the
Durnin-Womersley equation to predict body density from the sum of four skinfold thicknesses and the Siri
equation to calculate % body.
a) For each of the following three subjects, compare their mean triceps and subscapular skinfold thickness
measure to the NHANES reference data in Lee & Nieman’s Nutritional Assessment, Appendix M & N. Record
their approximate percentiles below. (6 points)
Subject
Triceps
NHANES
Subscapular
NHANES
(mm)
percentile
(mm)
percentile
Sara
41.5
41.8
Joe
4.6
7.7
Maria
25.1
25.3
3
NUT 112: Lab 1
2014
Student name:
Lab TA: ____________________________________
b) For two of these subjects, you have measured their skinfold thickness at four sites. Melanie is a 32 year old
female and Shawn is a 19 year old male. Calculate the sum of skinfolds and the log sum of skinfolds in the table
below. (4 points)
Skinfold
Mean of two
measures (mm)
Skinfold
SHAWN:
Mean of two
measures (mm)
MELANIE:
Triceps (TSF)
4.6
Triceps (TSF)
41.5
Biceps (BSF)
1.9
Biceps (BSF)
10.9
Subscapular (SSSF)
7.7
Subscapular (SSSF)
41.8
Suprailiac (SISF)
8.1
Suprailiac (SISF)
39.8
Sum of four skinfolds
Sum of four skinfolds
Log10 of sum of four
skinfolds
Log10 of sum of four
skinfolds
c. The Durnin-Womersley equation (See Appendix 2) can be used to estimate body density from the sum of the
four skinfold measurements. Then, the Siri equation can be used to calculate % body fat from the density data.
Using the Durnin-Womersley and Siri equations to calculate body density and percent body fat for Shawn and
Melanie. (10 points)
Shawn (19 y/o male)
Body density
Calculations
Answer
Calculations
Answer
Percent body fat
Melanie (32 y/o female)
Body density
Percent body fat
4
NUT 112: Lab 1
2014
Student name:
Lab TA: ____________________________________
d. Comment on Shawn & Melanie’s percent body fat (refer to Table A2 in the Appendix). (4 points)
3. Mid-upper arm circumference, arm fat area and arm muscle area
For the following 2 subjects, calculate their arm fat area (AFA) and arm muscle area (AMA) using the formulas
in Appendix 2. Compare their mid-upper arm circumference (MUAC), AFA and AMA values to the NHANES
reference tables and report their approximate percentiles. Note: Rich is 23 y/o Caucasian male and James is a 37
y/o Caucasian male. (14 points)
TSF
MUAC
MUAC
Percentile
Rich
10.6 mm
31.9 cm
James
9.2 mm
30.8 cm
AFA
2
(mm )
AFA
Percentile
AMA
2
(mm )
AMA
Percentile
*Reference data tables are posted on SmartSite in the Body Composition Lab folder. There is also a reference
data tables for AMA in Lee & Nieman’s Nutritional Assessment, Appendix P.
(Show your work for full credit)
Rich
AFA:
James
AFA:
AMA:
AMA:
5
NUT 112: Lab 1
2014
Student name:
Lab TA: ____________________________________
4. Waist circumference measurement and waist-hip ratio
Deposition of excess fat in the abdomen is strongly associated with elevated risks of type-2 diabetes and cardiovascular disease. The ratio of the circumferences of the waist and the hip (the “waist-hip ratio”) also reflects the
distribution of adipose tissue in the upper trunk (intra-abdominal) and lower trunk (hip and buttocks). More
recent guidelines recommend the use of the waist circumference only. However, it is important to understand
both the measurement and interpretation of the waist-to-hip ratio as well as for waist circumference alone.
For the following three subjects, calculate the waist to hip ratio and interpret the individuals’ risk of disease
using the guidelines provided in the Appendix. (9 points)
Hip circ. (cm)
Waist circ.
(cm)
Rob
94.8 cm
107.2 cm
Thomas
92.0 cm
98.1 cm
Gina
94.5 cm
71.3 cm
Subject
Risk of disease based
on waist circumference
Waist to
hip ratio
(WHR)
Risk of disease
(based on WHR)
5) Interpretation of BIA results
a) Jayson is a 22 year old male with a height of 175.1 cm and weight of 83.10 kg. Below are the results from
his BIA analysis. The machine that was used to measure Jayson only reports body water results. Assuming that
the fat free mass is typically 73.2% water and that 1 L of water = 1 kg of mass, complete the table below to
calculate Jayson’s percent body fat. (6 points)
Measure
Value
Intracellular water (L)
21.73
Extracellular water (L)
17.14
Total body water (L)
38.87
Fat free mass (kg)
Fat mass (kg)
Percent body fat (%)
6
NUT 112: Lab 1
Student name:
2014
Lab TA: ____________________________________
b) Calculate Jayson’s BMI, and compare that to his % body fat from the BIA that you just calculated and the
results from his calculated % body fat from skinfolds (provided). Compare the consistency of the results for
these three indicators in terms of his risk for disease. Use the ranges in table A2 and A3 in the appendix of this
lab packet to indicate his risk of disease. (5 points)
Value
Risk category
BMI
% body fat from BIA
% body fat from skinfolds
27.5%
c) Comment on the consistency of results from the three techniques, with regard to disease risks implied. (For
example, if the subject is a woman and has a percent body fat >31% and BMI > 30, then the results of the two
determinations are consistent.): (2 points)
d) What are possible reasons for any inconsistencies between the values observed (provide at least two reasons):
(2 points)
7
NUT 112: Lab 1
2014
Student name:
Lab TA: ____________________________________
Appendix 1: Cutoff values and interpretation
Table A1 - Classification of overweight and obesity by BMI (data from CDC)
BMI (kg/m2)
< 18.5
18.5 - 24.9
25.0 - 29.9
> 30.0
Classification of status
Underweight
Normal
Overweight
Obese
Table A2 - Interpretation percent body fat measures for men and women
Classification
Men
Unhealthy range (too low)
≤5%
Acceptable range (lower end)
6-15%
Acceptable range (upper end)
16-24%
Unhealthy (too high)
≥25%
Women
≤8%
9-23%
24-31%
≥32%
Table A3 – Interpretation of risk of comorbidities associated with obesity as determined by BMI (data from
WHO, 2000)
Risk category
BMI
Low (but risk of other clinical problems is increased)
<18.5 (underweight)
Average
18.5-24.9 (normal)
Increased
25-29.9 (overweight; pre-obese)
Moderate
30-34.9 (obese I)
Severe
35-39.9 (obese II)
Very severe
>40 (obese III)
Table A4: Classification of central obesity by waist circumference and waist to hip ratio
Risk category
Waist circumference
Waist-to-Hip Ratio
Men
Women
Men
Women
Low risk
<102 cm
<88 cm
≤1.0
≤0.85
At risk of disease
≥102 cm
≥88 cm
>1.0
>0.85
8
NUT 112: Lab 1
2014
Student name:
Lab TA: ____________________________________
Appendix 2: Equations
Body mass index:
𝐵𝑀𝐼 =
!"#$!!
!!"#!! !
Durnin-Womersley Equations to estimate body density (Db)
Age (y)
Equation
Males
17-19
Body density = 1.1620 – 0.0630 X log(Sum of skinfolds)
20-29
Body density = 1.1631 – 0.0632 X log(Sum of skinfolds)
30-39
Body density = 1.1422 – 0.0544 X log(Sum of skinfolds)
40-49
Body density = 1.1620 – 0.0700 X log(Sum of skinfolds)
50+
Body density = 1.1715 – 0.0779 X log(Sum of skinfolds)
Females
17-19
Body density = 1.1549 – 0.0678 X log(Sum of skinfolds)
20-29
Body density = 1.1599 – 0.0717 X log(Sum of skinfolds)
30-39
Body density = 1.1423 – 0.0632 X log(Sum of skinfolds)
40-49
Body density = 1.1333 – 0.0612 X log(Sum of skinfolds)
50+
Body density = 1.1339 – 0.0645 X log(Sum of skinfolds)
*Note: Equations were developed using the sum of the triceps, subscapular, suprailiac, and biceps skinfold
thicknesses
!.!"
% 𝑏𝑜𝑑𝑦 𝑓𝑎𝑡 = Siri formula to calculate % body fat from body density:
Calculation of Arm Muscle Area (AMA)*:
𝐴𝑀𝐴 =
Calculation of Arm Fat Area (AFA)*:
𝐴𝐹𝐴 =
!"#$! !×!"#
!!
− 4.50 ×100
!
!!
!"#×!"#$
!
−
!×!"# !
!
*Note: all units are in mm. Thus, you must convert the MUAC measurement (if measured in cm) to mm. For
example, a MUAC measurement of 31.5 cm is equal to 315 mm.]
9
NUT 112: Lab 1
2014
Student name:
Lab TA: ____________________________________
Appendix 3: Instructions for measurements1
Mid-upper arm circumference
1. Measurements should be recorded on the right arm. Ask the subject to stand with their elbow bent at a
90 degree angle. The subject may hold their arm across their abdomen or straight in front as shown in
Figure A1.
2. Measurement is midway between the acromion process of the scapula and the olecranon process
(Figure A1)
3. Take the measuring tape and measure this full distance. Divide the measurement in half and make a
small mark on the subject’s skin to indicate the mid-point of the upper arm.
Figure A1: Location of the mid-point of the upper arm
4. Ask the subject to relax their arm and let it hang loosely at their side.
5. Place the measuring tape around the subject’s arm at the marked level.
6. Be sure the tape is positioned at a 90 degree angle to the upper arm and parallel to the floor.
1
Instructions adapted from the NHANES Anthropometric Procedures Manual, January 2007
10
NUT 112: Lab 1
2014
Student name:
Lab TA: ____________________________________
Triceps and Biceps Skinfold Thickness
1. Ask the subject to turn so that you stand behind his or her right side (for triceps) or in front of his or her
right side (for biceps).
2. Ask the subject to stand upright with their weight evenly distributed on both feet, shoulders relaxed, and
the arms hanging loosely at the sides. Flexing or tightening the arm muscles will yield an inaccurate
measurement.
3. Using the same mid-point distance that you used for the MUAC, make one small mark on the back of
the subject’s upper arm over the triceps muscle and one small mark on the front of the arm over the
biceps muscle.
4. Grasp the skinfold: Using your thumb and index finger, grasp a fold of skin and subcutaneous adipose
tissue approximately 2.0 cm above the mid-arm circumference mark (See Figure A2) If you have
difficulty separating the skinfold from the triceps muscle, start at the elbow where the tissue tends to be
looser and work your way up to the mark. Ensure that the skinfold consists of a double thickness and
sits parallel to the long axis of the arm.
5. Position the caliper: Holding the skinfold 2.0 cm above the circumference mark, place the tips of the
caliper jaws over the complete skinfold. Ensure that the mark remains centered between the tips and that
the jaws sit perpendicular to the length of the skinfold. See Figure A2.
Figure A2: Measurement of triceps skinfold thickness
6. Take the measurement: Continue to hold the skinfold in place and release the caliper handle to exert full
tension on the skinfold. Wait 3 seconds for the needle on the caliper dial to settle on an accurate
measurement. Read the thickness to the nearest 0.1 mm.
7. Take care when releasing the caliper. Carefully open the jaws of the caliper and then remove it from the
skinfold. Do not drag the closed caliper off the skinfold.
11
NUT 112: Lab 1
Student name:
2014
Lab TA: ____________________________________
Subscapular skinfold thickness
1. Similar to the triceps skinfold measure, turn the subject so that you stand behind his or her right side.
Have the participant stand upright with their weight evenly distributed on both feet, the shoulders
relaxed, and the arms hanging loosely at the sides.
2. It is best to do this measure on bare skin. A light tank-top may be worn so that the back shoulder blade
is visible. If uncomfortable with this procedure, students may measure each other over a light T-shirt
for this lab exercise. Recognize that all measurements will be biased towards a higher value when
measured in this way.
3. Palpate for the inferior angle, or triangle portion, of the right scapula. Make a small mark on the
subject’s skin at the location of the inferior angle of the scapula.
4. Grasp the skinfold using your thumb and index finger. Grasp a fold so that your index finger remains
situated roughly 2.0 cm above and medial to the inferior angle of the scapula. The fold should be
roughly diagonal across the subject’s back, parallel to the inferior angle of the scapula. Due to tightness
in this area of the back on many subjects, obtaining this skinfold measure can be a challenge. In these
cases where you experience difficulty separating the subscapular skinfold from the underlying tissue,
begin grasping the fold with the thumb and index finger spread wide.
5. Continue to hold the skinfold in place. With the other hand, position the tips of the caliper jaws over the
complete fold at the position of your recorded mark, roughly 2.0 cm lateral to the fingers
6. Continue to hold the skinfold in place and release the caliper handle to exert full tension on the skinfold.
Wait 3 seconds for the needle on the caliper dial to settle on an accurate measurement. Read the
thickness to the nearest 0.1 mm.
7. Take care when releasing the caliper. Carefully open the jaws of the caliper and then remove it from
the skinfold. Do not drag the closed caliper off the skinfold.
Suprailiac skinfold thickness
1. The skinfold is measured just above the iliac crest at the midaxillary line on the right side. The fold
follows the natural cleavage lines of the skin and runs diagonally.
2. Ask the participant stand upright with their weight evenly distributed on both feet, the shoulders
relaxed, and the arms hanging loosely at the sides. The right arm may be flexed so that it is out of the
way of the anthropometrist.
3. Palpate the iliac crest (the top of the hip bone) on the midaxillary line. Make a small mark on the skin.
4. The measurer should grasp the skinfold about 1 cm posterior to the midaxillary line.
5. Continue to hold the skinfold in place. With the other hand, position the tips of the caliper jaws over the
fold at the position of the mark.
6. Continue to hold the skinfold in place and release the caliper handle to exert full tension on the skinfold.
Wait 3 seconds for the needle on the caliper dial to settle on an accurate measurement. Read the
thickness to the nearest 0.1 mm.
7. Take care when releasing the caliper. Carefully open the jaws of the caliper and then remove it from the
skinfold. Do not drag the closed caliper off the skinfold.
12
NUT 112: Lab 1
Student name:
2014
Lab TA: ____________________________________
Waist and hip circumference
1. Ask subject to remove any bulky outer clothing that might interfere with the measurements. For the
waist circumference, you may be able to access the area over bear skin. For hip circumference, light
clothing may be worn and the measurement recorded over the clothes.
2. Palpate the top of the iliac crest, as you have done with the suprailiac skinfold measurement and make a
small mark in this location (for waist circumference). For the hip circumference, locate the widest part
of the hips and buttocks.
3. Place an inelastic, flexible tape in a horizontal plane (parallel to the floor) around the abdomen at the
level of the marking.
4. Ask the participant stand upright with their weight evenly distributed on both feet, the shoulders
relaxed, and the arms hanging loosely at the sides.
5. The tape should be snug against the skin, but not so tight as to compress the skin.
6. Ask the subject to breathe normally and record the measurement at the end of a normal exhalation.
13