VALIDITY OF VARIOUS
BIOELECTICAL IMPEDANCE ANALYSIS (BIA)
ANALYZERS IN ASSESSING BODY FATNESS
AMONG HONG KONG UNIVERSITY STUDENTS
BY
CHAN YIU WA
03014339
AN HONOURS PROJECT SUBMITTED IN PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOR THE DEGREE OF
BACHELPR OF ARTS
IN
PHYSICAL EDUCATION AND RECREATION MANAGEMENT (HONOURS)
HONG KONG BAPTIST UNIVERSITY
MARCH 2006
15th March 2006
We hereby recommend that the Honours Project by Mr. Chan
Yiu Wa entitled “Validity of nine different bioelectrical
impedance analysis devices in assessing body composition of
Chinese university adults” be accepted in partial fulfillment
of the requirements for the Bachelor of Arts Honours Degree
in Physical Education and Recreation Management.
Associate Prof. Lobo. Louie Prof. B. Chow
Chief Advisor Second Reader
Process Grade:
Product Grade:
Overall Grade:
ACKNOWLEDGEMENTS
I would like to express my gratefulness to my chief advisor,
Associate Professor Hung Tak, Lobo Louie, for his kind and
professional suggestions throughout the whole project period,
especially his help in the part of statistical analysis.
Another person I want to give my thanks to is Mr. Binh Quach,
lab technician of Dr. Stephen Hui Centre for Physical
Recreation and Wellness, for guiding me in the use of the
laboratory equipment. Lastly, thank you for all the
participants for their sincere participation.
Chan Yiu Wa
Department of Physical Education
Hong Kong Baptist University
Date:
Abstract
Bioelectrical Impedance Analysis (BIA) is a rapid,
noninvasive, and relatively inexpensive technique for
evaluating body composition in field settings. The present
study attempted to determine the validity of 9 common BIA
analyzers which could be bought in most local department
stores. It included the following models: TANITA, CONAIR, OTO,
OSIM, HANSON, and Oregon Scientific, and the cost ranged
between HK$400 and HK$900. A total of 60 university students
volunteered as subjects, including 30 males and 30 females.
Each subject was asked to be assessed by means of Underwater
Weighing (UUW) utilizing the Siri equation to calculate their
body compositions, serving as the criterion. 9 commonly used
BIA analyzers were bought from local department stores and
were used to measure the body fat percentages. Correlation
coefficients as well as percent errors were computed between
the criterion and each of the BIA analyzers. All commonly used
BIA analyzers tended to overestimate the body fat percentages
significantly in both male and female subjects.
TABLE OF CONTENTS
CHAPTER Page
1. INTRODUCTION.....................................1
Statement of Problem......................... 3
Hypotheses................................... 4
Definition of Terms.......................... 4
Delimitation................................. 8
Limitation................................... 9
Significance of the Study.................... 9
2. REVIEW OF LITERATURE.............................11
Underwater Weighing (UWW).................... 12
Bioelectrical Impedance Analysis (BIA)....... 20
Summary...................................... 25
3. METHODOLOGY......................................27
Subjects..................................... 27
Body Height and Weight Measurements.......... 27
BIA Measurements............................. 28
UWW Measurement.............................. 29
Determination of Residual Volume............. 30
CHAPTER Page
Method of Analysis........................... 31
4. ANALYSIS OF DATA.................................33
Results...................................... 33
Discussion................................... 50
5. SUMMARY AND CONCLUSIONS..........................63
Summary of Results........................... 63
Conclusions.................................. 64
Recommendations.............................. 65
BIBLIOGRAPHY........................................66
APPENDICES..........................................70
A. Consent From to Participants.................. 70
B. Data Collection Form.......................... 72
LIST OF TABLES
TABLE Page
1. Physical Characteristics of the male Participants
(N = 30).........................................33
2. Physical Characteristics of the female Participants
(N = 30).........................................33
3. Correlation of the %BF results from BIA devices with
UWW in male participants.........................36
4. Correlation of the %BF results from BIA devices with
UWW in female participants.......................37
5. Correlation of the %BF results from BIA devices with
UWW for all participants.........................40
6. Comparison of Mean ± SD, mean difference (MD) by
Paired-sample t-test, and Standard Deviation
Difference (SDD) for the %BFF of each Prediction
Methods when compared with UWW in male
subjects........................................42
TABLE Page
7. Comparison of Mean ± SD, mean difference (MD) by
Paired-sample t-test, and Standard Deviation
Difference (SDD) for the %BFF of each Prediction
Methods when compared with UWW in female
subjects........................................43
8. Comparison of Mean ± SD, mean difference (MD) by
Paired-sample t-test, and Standard Deviation
Difference (SDD) for the %BFF of each Prediction
Methods when compared with UWW in all
subjects........................................46
LIST OF FIGURES
FIGURE Page
1. Scatter-plots showing the Correlation between TANITA
BF682, TANITA UM029, TANITA Ultimate Scale, HANSON
HFX50, OTO WS001 and UWW in %BF for all subjects
(n=58)...........................................48
2. Scatter-plots showing the Correlation between CONAIR
C8991H, CONAIR C8976H, Oregon Scientific GA101, OSIM
OS1100, TANITA TBF410 and UWW in %BF for all subjects
(n=58)...........................................49
Chapter 1
INTRODUCTION
Fat is one of our body’s essential nutrients. But too much
or not enough fat leads to problems. Too much fat in our body
increases the risk of cardiovascular diseases (U. S.
Department of Health and Human Services, 1988). But not enough
body fat is also risky. Fat was necessary to cushion joints,
protect organs, help regulate body temperature and provide
energy. Some of the essential lipids, like phospholipids, were
needed for cell membrane formation. Nonessential lipids are
required in storage of vitamins, nervous system, menstrual
cycle and reproductive system (Heyward & Stolarczky, 1996).
We all needed some body fat to function optimally. So, health
professionals needed to understand how much fat their patients
needed to have, and had a fast and accurate method to assess
body composition.
Due to the slim business in Hong Kong, people in the city
take much more care in their body weight. Not only for weight
reduction, the sport industry in Hong Kong has becomes more
scientific. Sport experts would try their best to control
athletes’ body composition in a best condition. Excess body
fats affect sports performance. So, accurate devices for
detecting body fat become much more important in recent years.
In health and fitness industry, it can show a healthy standard
for a suitable body fat percentage. For competition aspects,
it is a good tool to set athletes weight, and determine the
best diet for specific athletes.
We need a method that can determine percentage body fat
in a fast and convenient way. Underwater weighing (UWW) was
an accurate method, but the procedure is slow and
inconveniences (Lisa, 2001). And the specific device made it
impossible to take place in different areas. New methods like
Bioelectrical Impedance Analysis (BIA) were developed for
body fat analysis. BIA is a rapid, noninvasive, and relatively
inexpensive technique for evaluating body composition in
field settings. There are various types of BIA machines in
the market, which could be afforded by most of the people.
They might use different methods to detect body fat. But errors
might exist. The present study attempted to determine the
validity of 9 common BIA analyzers which could be bought in
most local department stores. It included the following models:
TANITA, CONAIR, OTO, OSIM, HANSON, and Oregon Scientific, and
the cost ranged between HK$399 and HK$895, which could be
afforded by general public. The technology in BIA machines
was well developed, and there were many types of BIA machines
available in the local market. In this study, we would like
to use these nine different models of leg-to-leg BIA devices,
and compare the results got from UWW. As UWW is a fat testing
method that has been scientifically validated, and considered
as a “gold standard” (Clark, Kuta & Sullivan, 1993). We would
like to find out the validity of the leg-to-leg BIA devices,
and the possible factors that may affect the results.
Statement of the problem
The main purpose of this study was going to validate 9
different leg-to-leg BIA machines, using underwater weighing
as the criterion method, in order to provide scientific
information to the public to choose the appropriate BIA
machines. University students would be chosen as the target
group for the present investigation.
Hypotheses
In this study, hypotheses all the BIA machines available
in common department stores would be valid equipments in
assessing percentage body fat (%BF) for university
undergraduate students. And we would look for the correlation
of the BIA scales and UWW method.
Definition of Terms
For a better understanding of this study, the terms that
would be used commonly were defined as follow:
Body Composition
Body composition was a component of physical fitness. It
refers to the absolute and relative amounts of muscle, bone
and fat tissues composing body mass (Heyward, 1991).
Two-component Model
The two-component model is the system dividing human body
into 2 components, fat and fat-free compartment (Anshel,
Freedson, Hamill, Haywood, Horvat, & Plowman, 1991).
Fat Body
Fat body includes all extractable lipids from adipose and
other tissues in the body (Heyward & Stolarczky, 1996).
Fat Mass (FM)
Fat weight is the total weight of the fat body (Heyward
& Stolarczky, 1996).
Fat Free Body (FFB)
Fat free body includes all residual, lipid-free chemicals
and tissues, including water, muscle, bone connective tissue
and internal organs (Heyward & Stolarczky, 1996).
Fat Free Mass (FFM)
Fat free weight is the total weight of the fat free body
(Heyward & Stolarczky, 1996).
Lean Body Mass (LBM)
Lean body mass equals to FFM plus essential lipids (Heyward
& Stolarczky, 1996).
Relative Body Fat (%BF)
The FM expressed as a percentage of total body weight
(Heyward & Stolarczky, 1996).
Essential Lipids
Compound lipids (phospholipids) needed for cell membrane
formation, consists of about 10% of total-body lipid (Heyward
& Stolarczky, 1996).
Nonessential Lipids
Triglycerides found primarily in adipose tissue, consists
of about 90% of total body lipid (Heyward & Stolarczky, 1996).
Total Body Density (BD)
Total body mass expressed relative to total body volume
(Heyward & Stolarczky, 1996).
Body Mass Index (BMI)
It is the ratio of body weight, in kg, to the square of
height, in meter (kg/m²). It gives a gross estimate of
appropriateness of weight for certain height. It is also used
as assessing growth and nutritional status (Anshel, et al.,
1992).
Bioelectric Impedance Analysis (BIA)
BIA is a device used as determining body composition. A
specific amount of electrical current is transmitted through
the body, and the device calculates the resistance (impedance)
of the body. As fat is a poor conductor of electricity,
resistance is directly related to the amount of fat in the
body. The resistance is also related to the length (height)
and cross-sectional area (weight) of the conductor (body).
These data are required in predicting percentage body fat
(Anshel, et al., 1992).
Underwater Weighing (UWW)
UWW is a criterion method to measure body fat percentage.
It based on Archimedes’ principle, estimate body fat
percentage by measuring body density. Subjects were weighted
out of and fully submerged in water. The underwater weight
is corrected for residual volume, gastrointestinal gas, and
water temperature. Body fat percentage is calculated by the
body density in Brozek or Siri equation. It is also called
as hydrostatic weighing (Anshel, et al., 1992). It was
referred as the “gold standard” for validating other indirect
methods for assessing body composition (Going, 1996).
Residual Volume (RV)
Residual volume is the amount of air remained in the lung
after maximal exhalation (Martini, 2004).
Gastrointestinal Gas
Gastrointestinal gas is the gas trapped in the
gastrointestinal tract (Heyward, 1991).
Delimitations
A total of 30 Chinese male and 30 Chinese female university
students form Hong Kong Baptist University were involved in
this pilot study. Due to time and financial constraint, the
population size was limited to 60. All the subjects were
measured using underwater weighing and the 10 Bioelectrical
Impedance Analysis (BIA) devices, in the Dr. Stephen Hui
Centre for Physical Recreation and Wellness located at Hong
Kong Baptist University. Residual volume was measured for
calculation of body composition. The percentage body fat data
measured were used for statistical analysis, for the purpose
of examine the validity of the BIA devices, compared with
Underwater Weighing.
Limitations
The following limitations were understood for the purpose
of interpreting this pilot study:
1. The sample of subjects was limited to Hong Kong Baptist
University students, aged from 19 to 24.
2. We assumed that all of the subjects were biologically
matured.
3. Data were collected during different dates and time.
4. The two-component model of body composition was
assumed.
Significance of Study
Due to the advanced technology, Bioelectrical Impedance
Analysis (BIA) devices became a common machine appeared in
the market. We could find many different BIA devices in
department stores, or some health related shops. Different
models have their different formula to analysis percentage
body fat. But some of the models might not design for Chinese
populations. So, in this pilot study, we would compare these
devices to determine which one would be the best prediction
for Chinese population.
Chapter 2
REVIEW OF LITERATURES
Bioelectric impedance analysis (BIA) system was developed
in the 1960s-1970s. Experts had conducted many investigations
on BIA, and other body fat analysis methods. There were direct
and indirect methods to measure body composition. BIA was one
of the indirect methods which were comparatively easier to
process. And many formulas were developed in order to fit most
of the population. In this study, the main purpose was to
investigate the validity of nine different leg-to-leg BIA
devices, which were available in the market, when compared
with underwater weighing (UWW). UWW was used as a criterion
method for validation. We would like to find out the best BIA
device which fit our target population, 19-24 adults in both
genders.
In this chapter, we would focus on reviewing the past
literatures which was correlated with our study’s topic. In
the following, it will be divided into two parts. The first
one was about underwater weighing (UWW), where the second one
was about bioelectric impedance analysis (BIA).
Underwater Weighing (UWW)
In this study, our calculations on the subjects’ percentage
body fat were base on the two-component model. In order to
study body composition, the body weight needed to divide into
two or more compartments. In most of the researches in body
composition, the two-component model and the chemical
four-component model were used generally (Heyward &
Stolarczky, 1996).
Two-component Model
Theoretical models were used to obtain reference measures
of body composition for the development of anthropometric,
BIA, skinfold method and equation. The classic two-components
separated the body into fat and fat free body compartments.
The fat consisted of all extractable lipids and the fat free
body included protein, mineral and water components (Siri,
1961). Although the chemical four-component model was widely
used, we had chose two-component model in this study, since
the calculation was more convenience, and we could concern
less about the subjects’ chemical difference. This
two-component model was served as the foundation for the
underwater weighing method (Heyward, 1991). Based on this
model, human bodies were divided into two compartments, the
fat body and the fat free body (FFB).
In order to apply this two-component model, the following
assumptions were required (Brozek, Grande, Anderson & Keys
1963; Siri, 1961):
1. The density of fat is 0.901 g/cc, and the density
of FFB is 1.10 g/cc.
2. The densities of fat and the FFB components (water,
protein, minerals) in all individuals remain
constant.
3. The densities of the tissues comprising the FFB are
constant within an individual, and their
proportional contribution to the lean component
remains constant.
4. The individual being measured differs from the
reference body only in the amount of fat. The FFB
of the reference body is assumed to be 73.8% water,
19.4% protein, and 6.8% mineral.
Based on the above assumptions, Siri (1961) developed an
equation that could be derived to convert one’s total body
density (BD) from underwater weighing into relative body fat
proportions (%BF). The equation was as follows:
%BF = [(4.95/BD) – 4.500] ╳ 100 (Siri, 1961)
Later on, Brozek et al. (1963) also developed an equation
that assumed the density of fat was 0.88876 g/cc, and the
density of the FFB was assumed to be 1.01033 g/cc. The equation
was as follows:
%BF = [(4.57/BD) – 4.142] ╳ 100 (Brozek et al., 1963)
Assumptions and the Validity of Underwater Weighing
The validity of the estimation of body fat from body density
depended on the following assumptions:
1. The densities of the constituents of the body were
relatively constant from person to person (Going,
1996).
2. The separate densities of the body composition were
additive (Going, 1996).
3. The proportions of the constituents other than fat were
relatively constant from person to person (Going,
1996).
UWW as the Gold Standard
In the field of assessing body composition, UWW and
dual-energy x-ray absorptiometry (DEXA) were the only methods
that had been scientifically validated. These two methods were
considered as the “gold standard”. All other indirect method
of assessing body composition was validated using the gold
standard (Clark, Kuta & Sullivan, 1993). In this pilot study,
UWW was used as the criterion method. And we had chose Siri’s
(1961) equation to estimate %BF from the BD obtained form UWW.
Many Researchers considered the method of Siri (1961) and
Brozek et al. (1963) predicting %BF from BD based on the two
component model as the “gold standard” for assessing body
composition. Besides UWW often had been used as the criterion
method in validation studies of new body composition
assessment methods (Going, 1996).
Since DEXA devises were too expensive, when comparing the
cost and effectiveness, UWW was the most common method used
in a laboratory setting, for assessing body composition
(Baumgartner & Jackson, 1995).
Principle of UWW
According to Katch and Katch (1980), body weight, body
volume measurement and residual volume were the three main
components that constitute the computed body density score.
UWW for assessing body fat based on the Archimedes’ Principle
and the two-component model. By the Archimedes’ Principle,
when the body immersed in a fluid, the buoyancy force acted
on the body was evident by a loss of weight equal to the weight
of the displaced fluid. Therefore, when a subject was
submerged in water, body volume was equal to the loss of weight
in water, corrected for the density of water corresponding
to the temperature of water at the time of the submersion (Going,
1996). As body density (BD) = Mass / Volume, we could find
the density of the subjects.
The main objective of UWW was to measure percentage body
fat. This could be done by calculating BD from body volume
and body weight. Then BD could be translated into %BF by using
the traditional equations, such as the equation from Siri
(1961) or Brozek et al. (1963). By the equation of Goldman
and Buskirk (1969), BD could be found:
BD = MA / {MA – MW – (RV – 100) ╳ WD}
Where MA was the mass of body in air in g, MW was the mass of
the body under water in g, WD was the density of water, RV
stand for the residual volume of the subject in ml, and the
value “100” was the estimated value of air trapped in the
gastrointestinal tract. Based on the two-component model,
body was separated into fat body and fat-free body. As their
densities were different, the percentage of fat could be
calculated.
For the height and mass of body in air, it could be measured
by some valid and reliable devices, like Detecto stadiometer
and beam balance scale. For the mass under water, the subject
needed to seat on a chair assembly suspended from an autopsy
scale, or be seated or kneeled on a weighing platform supported
by a force transducers (Going, 1996).
The underwater weighing system originally described by
Goldman and Buskirk in 1961. This system had gained widespread
use (Going, 1996). The system used a rectangular weighing
platform made from 1 inch aluminum pipe and galvanized
hardware cloth of 1/2 inch mesh suspended from four load cells
mounted on a 2 inch rim surrounding the top of a welded aluminum
(1/4 inch stock) tank. The weighing platform could be set on
load cells that were sealed and mounted under the water on
the bottom of the tank. But these kinds of systems were
expensive (Going, 1996).
During the UWW process, the weight obtained would have
fluctuations. We had administered at least three to ten trials,
and we averaged the highest 3 trials within 0.1 kg (Heyward,
1991). This mass subtracted the mass of the chair or the others
supportive devices under water would be the subject’s weight
under water.
Measurement of residual volume (RV) was very important in
assessing changes in body density (Katch & Katch, 1980). RV
could be measured by gas dilution methods. Either the closed
circuit approach or the open circuit approach could be used.
In fact there was a dilution and eventual equilibration of
an inert traces or indicator gas such as nitrogen, helium or
oxygen. This technique had the advantage of being very rapid,
hence it had gained widespread use (Going, 1996). For the open
circuit approach where nitrogen was washed out of the lungs
during a specified period of oxygen breathes. Both of these
two approaches yielded precise estimates of residual volume
and with appropriate equipment and procedural modifications
can be used to estimate residual volume with the subject either
inside the tank outside the tank, which was measured on land
(Going, 1996). In this pilot study, Sensor Medics Vmax series
was used for determine residual volume, which was on land.
Katch and Katch (1980) stated that in the case of a single
residual volume score, a low score would be considered truer
or better than a higher one.
In the equation of Goldman et al. (1961), the density of
water was also included. Since water density varied with water
temperature, we needed to check the water temperature before
the test procedure began.
So, in order to calculate an individual’s BD, weight in
air, weight under water, residual lung volume and water
temperature were required.
Bioelectrical Impedance Analysis (BIA)
BIA was a noninvasive, rapid, and relatively inexpensive
method for assessing body composition (Heyward & Stolarczky,
1996). It now became a common devices used in laboratory, sport
training center, or even some beauty salon. Although the
relative predictive accuracy of the BIA method was similar
to the skinfold method, BIA might be a more preferable method
as it did not required a high degree of technical skill, it
is generally more comfortable and did not intruded the
client’s privacy, and it could be used for obese populations
(Gray, Bray, Gemayel, & Kaplan, 1989). In this pilot study,
we would like to compare the validity of different BIA devices.
Father of BIA
Thomasett (1962) worked on the basic BIA principle on the
early 1960’s. As Hoffer, Meador, and Simpson (1969) indicated
that there was a strong relationship between total body
impedance and total body water (TBW). They suggested that BIA
might be a valuable tool for assessing body composition.
At the most beginning, BIA devices were connected on the
arm and leg on one side of the body. Nowadays, there were BIA
devices connected with leg-to-leg and arm-to-arm. In this
study, we just focused on the leg-to-leg type BIA devices.
Principle of BIA
BIA devices looked like traditional bathroom scales, and
in one respect, acted like them too. They weighted the body
when they were stepped on. But placing the feet on a BIA scale
also put them in contact with electrodes that sent a small
and undetectable electrical current through the body. The
scale compared the current entering the body with the current
leaving it and calculated body fat composition using
bioelectric impedance analysis (BIA), which was based on the
difference in the ways that an electrical current was affected
by muscle and fat. The reason was that muscle was about 75
percent water and a good electrical conductor. In our body,
fat free mass (FFM) included the protein matrix of adipose
tissue, contained most of the water (~73%) and electrolytes
in the body, it made FFM a better conductor of electricity
than fat(Heyward & Stolarczky, 1996). While fat, which was
only about 20 percent water, which was a poor conductor. The
basic operation of BIA based on the body’s impedance. Since
water and electrolytes in the body were good conductors of
electricity. In fact, fat was such a poor conductor that the
original electrical current was diminished as it traveled
through fat. Human body contained intracellular and
extracellular fluids, which capable for electrical conduction
with cell membranes acted as electrical condensers or
capacitors (Heyward, 1991). Impedance was a measure both of
this resistance and of reactance, the ability of body tissue
to hold a charge and thus delayed its passage through the body.
Generally, the faster the current moved through the legs and
the body, the less resistance it encountered, the thinner the
individual was. BIA devices used a very weak electric current
to determine how thin or fat an individual was. Because muscle
and fat had different electrical properties, the current
passed through the body would be affected more or less
depending on the proportions of muscle and fat. By combining
this information with data like sex, age, height, weight and
comparing these with data from the general population, a
body-fat percentage could be determined.
So, the resistance of the body could be used to estimate
percentage body fat based on the above relationship. BIA
devices measured the body’s resistance and reactance, for
calculation of the resistance index (squared height /
resistance). FFM was then predicted (Lukaski, Johnson,
Bolonchuk, & Lykken, 1985).
In different types of BIA devices, different data were
required to input for %BF prediction. It based on different
equations installed into the machines, which was developed
by researchers for different populations. Athletic mode
became more common nowadays, which was for the use of some
elite athletics with fewer body fats.
Factors influenced BIA accuracy
There were numbers of variables which could influence the
BIA %BF estimation. Factors like the volume and distribution
of body water, surface electrolyte content, skin temperature,
or even blood distribution could bias BIA calculation (Segal,
Gutin, Presta, Wang & Van Itallie, 1985). The precision and
accuracy of the BIA measurements were affected by
instrumentation, technician skill, client factors and
environmental factors (Heyward, 1991). A major source of error
in BIA method was variability due to the subject’s state of
hydration. Eating, drinking and dehydration alter the
individual’s hydration state, thereby affecting total body
resistance and the estimation of fat free mass (Heyward, 1991).
Body resistance measurement 2 to 4 hours after a meal over
predicted the fat free mass of an individual by almost 1.5
kg (Deurenberg, Westrate, Paymans, & van der Kooy, 1988).
Exercise was another major factor that affected BIA
estimation. But the effect depended on the intensity and
duration of the exercise workout. Researchers reported that
jogging and cycling at moderate intensities (~70% VO2 max) for
90 to 120 minutes decrease body resistance. It would result
in a large overestimation of fat free mass (~12 kg) (Khaled,
McCutcheon, Reddy, Pearman, Hunter, & Weinsier, 1988). The
decrease of body resistance after exercise reflected that the
relatively greater loss of body water in the sweat and expired
air, compared to the loss of electrolytes. This leaded to a
higher electrolyte concentration in body’s fluid, therefore
decreasing body resistance values (Deurenberg et al., 1988).
And skin temperature and skin blood flow altered by exercise
also would alter the BIA results (Liang, Su, & Lee, 2000).
Summary
From the literature review above, we understood that UWW
was often used as the gold standard for determining body
composition when we wanted to judge with some indirect
techniques. But it was a relatively expensive and time
consuming process. For the view of popularity, experts found
ways to predict %BF, like BIA, which was more rapid,
noninvasive, and relatively inexpensive. New models which
were available in the market became more affordable. People
could assess their body composition in an economic way, and
in long term, control the problem of being overweight. But
certain factors would affect accuracy of BIA scales in
assessing %BF.
Chapter 3
METHODOLOGY
Subjects
Thirty Chinese male and thirty Chinese female university
students, aged 19-24 from the Hong Kong Baptist University
were invited to participate this study. Informed written
consent was obtained prior to initiating the testing protocols
voluntarily. Investigation components included body height
and weight measurements, percentage body fat measurement
using nine different BIA devices from six different
manufacturers, that were available in Hong Kong market, a
TANITA BIA machine in the laboratory, and UWW measurement.
Subjects were required not to eat 2 hours before the test began,
and did not drink fluid unless they felt thirsty. All tests
for each single individual were conducted within the same day.
Body Height and Weight Measurements
Body height was obtained by a wall mounted stadiometer,
to the nearest 0.5 cm. Body weight was obtained by TANITA TBF410
BIA scale, to the nearest 0.1 kg. Participants were instructed
to stand in an erect and eye-front posture, with heels together
at the center of the horizontal platform. They were also
required to wear swimming clothes when processing the tests.
BIA Measurement
Participants were required to stand in an upright position,
looking forward and with feet on the footpad electrodes on
ten different types of BIA devices, followed with the
instruction manuals. Nine of them were bought from the market,
and one of them was the laboratory’s equipment. The models
of the BIA devices were: 1) TANITA BF-682, 2) TANITA UM-029,
3) TANITA Ultimate Scale (TANITA Corp., Tokyo, Japan), 4)
HANSON HFX50 (HANSON UK Ltd), 5) OTO WS-001 (OTO Bodycare Pte.
Ltd., Singapore), 6) CONAIR C8991H, 7) CONAIR C8976H (CONAIR,
New York, USA), 8) Oregon Scientific GA101 (Oregon Scientific
INC., USA), 9) OSIM OS-1100 (OSIM International Ltd.,
Singapore), which were purchased in Hong Kong department
stores, which prices ranged from HK$400 to 900. TANITA TBF-410
(TANITA Corp., Tokyo, Japan) was installed in the laboratory.
In each single test, non-athletic adult model was selected
and the subject’s height and sex was input into each monitor.
Results obtained were recorded. And the subjects were required
to fulfill all the BIA tests in the same 15 minutes interval
in the same day. Alcohol pads were used to clean up the footpad
of the BIA devices.
UWW Measurement
Prior to measurement, the Chatillon autopsy scale (0-9 kg)
was calibrated. The water temperature in the tank was adjusted
to 34-36oC. Participants were measured in swimming brief.
Before entering the tank, they were asked to void their
bladders and to defecate if necessary. And they were required
to shower their bodies. After entering the tank, participants
needed to wet their bodies completely. And they were told to
rub over their entire body with their hands, in order to remove
any trapped air bubbles in hair, skin and swimming brief. Then,
he or she would be seated securely on the nylon sit web hung
from the scale. They were instructed to immerse completely
in the water and to produce maximal exhalation for every trail.
Also, subjects were instructed to lower their head to avoid
their heads above water level. When bubbles stopped appearing
from the participant’s month, tester would record the reading.
The average of the three highest readings within 100 g was
obtained. Water temperature was recorded for determining
water density. The weight of the nylon sit web was also
determined for calculation of the individual’s true
underwater weight.
Body density was determined by underwater weight using the
equation of Goldman et al. (1961). Percentage body fat was
estimated from body density by the equation of Siri (1961).
Determination of Residual Volume
Sensor Medics Vmax Series 2130 Spirometer, V6200 Autobox
and 6200 Autobox DL were used for determination of residual
volume (RV). The machine was calibrated before the tests began.
Individual’s name, age, height, weight, race were inputted
into the program. Plethysmography program was used to
determine RV. Then the participant prepared to attach a nose
clip and sat comfortable on a chair in a chamber, which would
not affect the breath. Then, a mouthpiece was inserted and
the participant was breathing the air in the chamber. At the
beginning, the participant was told to breathe normally. After
a signal given by the tester, the participant inhaled and
exhaled once maximally. Then remained normal breathe. After
that, a signal was given to the participant to pant fast and
slightly. Signal was given to the participant to stop panting
and remain normal breathe. Finally, the participant was told
to give a maximal inhalation and exhalation. The individuals
RV would be shown by the program. And a new mouthpiece with
filter was given to each participant.
Method of Analysis
In this pilot study, the results from different BIA devices
were compared with that of UWW. Lohman (1984) suggested that
a number of variables including the mean ± standard deviation
(SD), mean difference (MD), standard deviation difference
(SDD), correlation coefficient (r), standard error of
estimate (SEE) and total error (TE) should be included.
Collected data were analyzed by the “Statistic Package of
Social Science 13.0 for windows” (SPSS 13.0) software. As the
%BF calculated from UWW was the criterion method, all other
%BF results came from different BIA devices were compared as
UWW was the prediction method. Results were compared using
the Pearson product-moment coefficient correlation. Besides,
body weight, age and body mass index (BMI) were entered as
descriptive statistics. Also, a paired samples t-test was used
to determine if there was a significant difference in the %BF
means of the UWW and all of the BIA methods.
Chapter 4
ANALYSIS OF DATA
Results
The physical characteristics of the participants were
summarized in Table 1 and Table 2.
Table 1
Physical Characteristics of the male Participants (N = 30)
Minimum Maximum Mean ±SD
age 19 23 21 ±1.26
Weight(kg) 53.61 98.05 68.52 ±8.85
Height(cm) 163 194 174.43 ±6.98
BMI 17.6 27.1 22.42 ±2.21
RV(L) 1 2.59 1.73 ±0.35
Table 2
Physical Characteristics of the female Participants (N = 30)
Minimum Maximum Mean ±SD
age 19 24 21.03 ±1.4
Weight(kg) 45.8 65.9 53.25 ±5.49
Height(cm) 153.5 171 162.75 ±4.14
BMI 16.7 24.7 20.02 ±1.82
RV(L) 0.77 2.05 1.40 ±0.25
The age of the male participants were ranged from 19-23 years
old with a mean age of 21 years old and a standard deviation
of 1.26 years. The age of the female participants were ranged
from 19-24 years old with a mean age of 21.03 years old and
a standard deviation of 1.40 years. The weights of the male
participants were ranged from 53.61-98.05 kg with a mean
weight of 68.52 kg and a standard deviation of 8.85 kg. The
weights of the female participants were ranged from
45.80-65.90 kg with a mean weight of 53.25 kg and a standard
deviation of 5.49 kg. The heights of the male participants
were ranged from 163-194 cm with a mean height of 174.43 cm
and a standard deviation of 6.98 cm. The heights of the female
participants were ranged from 153.5-171 cm with a mean height
of 162.75 cm and a standard deviation of 4.14 cm. The BMI of
the male participants were ranged from 17.6-27.1 with a mean
BMI of 22.42 and a standard deviation of 2.21. The BMI of the
female participants were ranged from 16.7-24.7 with a mean
BMI of 20.02 and a standard deviation of 1.82. For residual
volume (RV), male participants had a RV ranged from 1 to 2.59
L, mean RV of 1.73 L and Standard deviation of 0.35 L. Female
participants had RV ranged from 0.77 to 2.05 L, as mean RV
was 1.40 L and Standard deviation of 0.25 L. These five
categories represented a wide range of physical
characteristics and body types.
The Pearson correlation coefficient of the results from
both gender were shown in Table 3 and 4. All the %BF results
from the BIA analysis results were compared with UWW method.
Table 3
Correlation of the %BF results from BIA devices with UWW in
male participants
BIA models n r p
TANITA BF682 28 0.647** 0.000
TANITA UM029 28 0.638** 0.000
TANITA ULTIMATE SCALE 28 0.663** 0.000
HANSON HFX50 28 0.602** 0.001
OTO WS001 28 0.564** 0.002
CONAIR C8991H 27 0.525** 0.005
CONAIR C8976H 28 0.603** 0.001
Oregon Scientific GA101 28 0.640** 0.000
OSIM OS1100 28 0.530** 0.004
TANITA TBF410 28 0.649** 0.000
**Correlation is significant at the 0.01 level (2-tailed).
Table 4
Correlation of the %BF results from BIA devices with UWW in
female participants
BIA models n r p
TANITA BF682 30 0.647** 0.000
TANITA UM029 30 0.555** 0.001
TANITA ULTIMATE SCALE 30 0.627** 0.000
HANSON HFX50 30 0.603** 0.000
OTO WS001 30 0.433* 0.017
CONAIR C8991H 30 0.446* 0.014
CONAIR C8976H 30 0.482** 0.007
Oregon Scientific GA101 30 0.602** 0.000
OSIM OS1100 30 0.398* 0.030
TANITA TBF410 30 0.648** 0.000
**Correlation is significant at the 0.01 level (2-tailed).
* Correlation is significant at the 0.05 level (2-tailed).
From Table 3 and 4, we could see the correlations and
significant values, as most of the BIA devices could give
significant data about the subjects’ %BF. In male subjects,
all the correlations were significant at the 0.01 level (p
< 0.05). In female subjects, most of the correlations were
at the 0.01 level, as only some of them fell within the 0.05
level. For the correlation coefficients between UWW and
TANITA BF682, the Pearson correlation value was 0.647 in male,
where the value in female was 0.647. For the correlation
coefficients between UWW and TANITA UM029, the Pearson
correlation value was 0.638 in male, as the value in female
was 0.555. For TANITA Ultimate Scale, the Pearson correlation
with UWW was 0.663 in male, and female was 0.627. These three
TANITA BIA devices, with TANITA TBF410, where the values were
0.649 and 0.648 respectively with male and female, gave
similar correlations. But the %BF results given by these
machines had significant difference with the results from UWW
(p < 0.05). For the others results, HANSON HFX50 had r value
0.602 in male, and 0.603 in female. OTO WS001 had values of
0.564 and 0.433 in males and females respectively. CONAIR
C8991H and CONAIR C8976H had r value at 0.525 and 0.603 for
male, and 0.446 and 0.482 for female respectively. CONAIR
C8891H gave the highest p value, 0.005 in male subjects. It
gave the closest results of %BF when compared with the other
BIA machines in male aspect. For Oregon Scientific GA101, the
r value in male and female were 0.640 and 0.602. Lastly, for
OSIM OS1100, r value in male was 0.530, and in female was 0.648.
OSIM OS1100 had the highest p value in female participants,
which was 0.030. It gave the closest results of %BF when
compared with the other BIA machines in female aspect.
In fact, all the BIA devices had a significant correlation
with UWW method, ranged from 0.398 to 0.649. Although TANITA
TBF410 in the laboratory was much more expensive (~HK$20000)
than the others household BIA, however, data indicated that
similar measurements were found between expensive device and
other inexpensive ones.
Table 5
Correlation of the %BF results from BIA devices with UWW for
all participants
BIA models n r p
TANITA BF682 58 0.793** 0.00
TANITA UM029 58 0.745** 0.00
TANITA ULTIMATE SCALE 58 0.787** 0.00
HANSON HFX50 58 0.697** 0.00
OTO WS001 58 0.503** 0.00
CONAIR C8991H 57 0.735** 0.00
CONAIR C8976H 58 0.470** 0.00
Oregon Scientific GA101 58 0.755** 0.00
OSIM OS1100 58 0.535** 0.00
TANITA TBF410 58 0.799** 0.00
**Correlation is significant at the 0.01 level (2-tailed).
From Table 5, it showed all the correlations of BIA scales
with UWW for all of the participants. TANITA BF-682 (r = 0.793),
TANITA UM-029 (r = 0.745), TANITA Ultimate Scale (r = 0.787),
HANSON HFX50 (r = 0.697), OTO WS-001 (r = 0.503), CONAIR C8991H
(r = 0.735), CONAIR C8976H (r = 0.470), Oregon Scientific GA101
(r = 0.755), OSIM OS-1100 (r = 0.535) and TANITA TBF410 (r
= 0.799) all gave a significant correlations with UWW at the
0.01 level of significant. Among all household BIA devices,
TANITA BF-682 had the highest r value. But overall, TANITA
TBF410 had the highest r value. However, the differences
between the two values were not large.
Table 6
Comparison of Mean ± SD, mean difference (MD) by Paired-sample
t-test, and Standard Deviation Difference (SDD) for the %BFF
of each Prediction Methods when compared with UWW in male
subjects.
Method n Mean ± SD MD t p SDD
UWW 28 8.64 ±4.04 / / / /
TANITA BF682 28 18.07 ±3.67 -9.43 -15.31 0.000 3.26
TANITA UM029 28 18.36 ±3.74 -9.72 -15.49 0.000 3.32
TANITA
Ultimate Scale 28 17.93 ±3.71 -9.29 -15.37 0.000 3.20
HANSON HFX50 28 19.51 ±4.92 -10.87 -14.11 0.000 4.08
OTO WS001 28 18.84 ±4.75 -10.19 -13.00 0.000 4.15
CONAIR C8991H 27 12.43 ±3.96 -3.68 -4.88 0.000 3.92
CONAIR C8976H 28 18.40 ±4.54 -9.76 -13.41 0.000 3.85
Oregon
Scientific
GA101
28 18.49 ±3.77 -9.85 -15.69 0.000 3.32
OSIM OS1100 28 20.09 ±2.94 -11.45 -17.23 0.000 3.52
TANITA TBF410 28 17.26 ±3.49 -8.62 -14.27 0.000 3.20
Table 7
Comparison of Mean ± SD, mean difference (MD) by Paired-sample
t-test, and Standard Deviation Difference (SDD) for the %BFF
of each Prediction Methods when compared with UWW in female
subjects.
Method n Mean ± SD MD t p SDD
UWW 30 17.23 ±5.37 / / / /
TANITA BF682 30 24.08 ±3.89 -6.85 -9.11 0.000 4.12
TANITA UM029 30 23.74 ±3.81 -6.51 -7.85 0.000 4.54
TANITA
Ultimate Scale 30 23.83 ±3.85 -6.60 -8.58 0.000 4.21
HANSON HFX50 30 24.16 ±3.93 -6.93 -8.74 0.000 4.34
OTO WS001 30 20.95 ±4.15 -3.72 -3.94 0.000 5.17
CONAIR C8991H 30 21.00 ±3.49 -3.77 -4.19 0.000 4.93
CONAIR C8976H 30 19.51 ±4.27 -2.28 -2.50 0.019 5.00
Oregon
Scientific
GA101
30 23.56 ±3.63 -6.33 -8.05 0.000 4.31
OSIM OS1100 30 22.00 ±2.59 -4.77 -5.28 0.000 4.95
TANITA TBF410 30 23.30 ±3.77 -6.07 -8.11 0.000 4.10
Although almost all BIA devices gave significant
correlation values with UWW, all the BIA devices overestimated
all the subjects’ %BF. Table 6 and 7 showed the mean difference
(MD) and standard deviation differences (SDD) in both male
and female subject groups.
For male subjects, all the means form BIA devices were
greater than UWW, ranged from 8.62 – 10.67 except CONAIR C8991H.
MD of CONAIR C8991H with UWW was 3.68, which had the closest
%BF results with UWW. It showed that in male populations of
19-24 age groups, CONAIR C8991H was relatively more accurate
when compared with the others BIA devices.
For male subjects, all the means form BIA devices were also
greater than UWW, ranged from 3.72 – 6.93 except CONAIR C8976H.
MD of CONAIR C8976H with UWW was 2.28, which had the closest
%BF results with UWW. It showed that in male populations of
19-24 age groups, CONAIR C8976H was relatively more accurate
when compared with the others BIA devices.
When comparing the results from male and female, we could
see that MD values of the BIA devices with UWW were greater
in male than that in female. It represented that those BIA
devices were comparatively more accuracy in assessing %BF for
female subjects in our target age group, 19-24 years old.
Then we would compare the BIA scales in the same brand.
There were 3 household TANITA BIA scales, TANITA BF682, TANITA
UM029 and TANITA Ultimate Scale and 1 laboratory BIA scale,
TANITA TBF 410. In male subjects, the Mean ± SD values were
18.07 ± 3.67, 18.36 ± 3.74, 17.93 ± 3.71, and 17.26 ± 3.49
respectively. In female subjects, the Mean ± SD values were
24.08 ± 3.89, 23.74 ± 3.81, 23.83 ± 3.85, and 23.30 ± 3.77
respectively. These scales gave close mean %BF values for the
same subject gender group. There were also 2 CONAIR scales
in this pilot study, which were C8991H and C8976H. In male
subjects, the Mean ± SD values were 12.43 ± 3.96, and 18.40
± 4.54 respectively. In female subjects, the Mean ± SD values
were 21.00 ± 3.49, and 19.51 ± 4.27 respectively. The mean %BF
values were closer in female than that in male. All the scales
had a negative t value with p < 0.05.
Table 8
Comparison of Mean ± SD, mean difference (MD) by Paired-sample
t-test, and Standard Deviation Difference (SDD) for the %BFF
of each Prediction Methods when compared with UWW in all
subjects.
Method n Mean ± SD MD t P SDD
UWW 58 13.08 ±6.41 / / / /
TANITA BF682 58 21.18 ±4.82 -8.09 -15.74 0.000 3.92
TANITA UM029 58 21.15 ±4.62 -8.06 -14.34 0.000 4.28
TANITA Ultimate
Scale 58 20.98 ±4.79 -7.90 -15.18 0.000 3.96
HANSON HFX50 58 21.91 ±4.98 -8.83 -14.54 0.000 4.63
OTO WS001 58 19.93 ±4.53 -6.84 -9.16 0.000 5.69
CONAIR C8991H 57 16.94 ±5.68 -3.73 -6.33 0.000 4.44
CONAIR C8976H 58 18.97 ±4.40 -5.89 -7.70 0.000 5.83
Oregon
Scientific
GA101
58 21.11 ±4.47 -8.03 -14.48 0.000 4.22
OSIM OS1100 58 21.08 ±2.90 -7.99 -11.18 0.000 5.45
TANITA TBF410 58 20.39 ±4.72 -7.30 -14.34 0.000 3.88
The mean ± standard deviation and MD for all subjects were
shown in Table 8. TANITA BF-682 (mean ± SD = 21.18 ± 4.82, MD
= 8.09), TANITA UM-029 (mean ± SD = 21.15 ± 4.62 ,MD = 8.06),
TANITA Ultimate Scale (mean ± SD = 20.98 ± 4.79 ,MD = 7.90),
HANSON HFX50 (mean ± SD = 21.91 ± 4.98 ,MD = 8.83), OTO WS-001
(mean ± SD = 19.93 ± 4.53 ,MD = 6.84), CONAIR C8991H (mean ±
SD = 16.94 ± 5.68 ,MD = 3.73), CONAIR C8976H (mean ± SD = 18.97
± 4.40 ,MD = 5.89), Oregon Scientific GA101 (mean ± SD = 21.11
± 4.47 ,MD = 8.03), OSIM OS-1100 (mean ± SD = 21.08 ± 2.90 ,MD
= 7.99) and TANITA TBF410 (mean ± SD = 20.39 ± 4.72 ,MD = 7.30),
all showed MD value about 6 to 8 except CONAIR C8991H. The
Mean difference of CONAIR C8991H and UWW in assessing %BF was
the smallest. All the scales had a negative t value as p <
0.05.
Figure 1 and 2 showed the relationships of %BF values
between UWW and the BIA devices for all subjects.
Figure 1
Scatter-plots showing the Correlation between TANITA BF682,
TANITA UM029, TANITA Ultimate Scale, HANSON HFX50, OTO WS001
and UWW in %BF for all subjects (n=58).
30.0020.0010.000.00
TANITA_BF682 (%BF)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
UWW
(%BF
)
LOI
30.0020.0010.000.00
TANITA_UM029 (%BF)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
UW
W (%
BF)
LOI
30.0020.0010.000.00
HANSON_HFX50 (%BF)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
UWW
(%BF
)
LOI
30.0020.0010.000.00
OTO_WS001 (%BF)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
UW
W (%
BF)
LOI
30.0020.0010.000.00
TANITA_UltimateScale (%BF)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
UW
W (%
BF)
LOI
LOI = Line of identity
Figure 2
Scatter-plots showing the Correlation between CONAIR C8991H,
CONAIR C8976H, Oregon Scientific GA101, OSIM OS1100, TANITA
TBF410 and UWW in %BF for all subjects (n=58).
30.0020.0010.000.00
CONAIR_C8976H (%BF)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
UW
W (%
BF)
LOI
30.0020.0010.000.00
OSIM_OS1100 (%BF)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
UW
W (%
BF)
LOI
30.0020.0010.000.00
CONAIR_C8991H (%BF)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
UW
W (%
BF)
LOI
30.0020.0010.000.00
Oregon_Scientific_GA101 (%BF)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
UWW
(%BF
)
LOI
30.0020.0010.000.00
TANITA_TBF410 (%BF)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
UW
W (%
BF)
LOI
LOI = Line of identity
The relationships between all the BIA scales in this study
with UWW method were shown on Figure 1 and 2, for all of the
subjects. All of the patterns illustrated that a positive
relationships between all the BIA scales and UWW. And the
points lie around LOI with more points on the right of the
line.
Discussions
The purpose of this pilot study was to examine the validity
of various BIA scales which was available in the market, for
Chinese adults aged 19-24. The criterion method used in this
pilot study was Underwater Weighing technique (Siri, 1961),
which is long referred to as the “gold standard” for validation
studies in the field of body composition assessment. The
subjects of this study were 60 Chinese university students,
including 30 males and 30 females. The present finding drawn
from this study might be limited to the homogenous sample and
physical characteristic of Chinese university students in
Hong Kong.
Characteristics of the Participants
Participants in this pilot study were students from the
Hong Kong Baptist University. They were all healthy adults
with an active lifestyle. The mean %Bf of the males and females
participants, measured by the UWW method, was 8.64 with a SD
of 4.04% and 17.23 with a SD of 5.37% respectively. When
comparing the mean %BF of the participants of this pilot study
to a study by Lee (1998) on Chinese male university students
with a mean age of 22.45 years old, the two mean %BF values
were very close that the mean %BF, also measured by UWW of
the participants of Lee (1998) was 9.88% with a SD of 2.647%.
Similarities between the two samples of population could be
found in terms of age, lifestyle, and occupation. These all
suggested that the mean %BF of the participants in the present
study was similar to that of the population of the same group.
However, it should be noted that there were 2 male participants
had a negative value of %BF. This might be a result of technical
error. These 2 data were excluded from data analysis as it
was not a reasonable value it would affect the analyzing
process.
Validity of BIA scales
The 9 different household leg-to-leg BIA scales and the
TANITA TBF410 in laboratory using a tetra-polar pressure
contact footpad electrode system, expect the 2 models form
CONAIR which is bi-polar and Oregon Scientific GA101, which
have 6 conductive pads.
For TANITA BF682, UM029, and the Ultimate Scale (TANITA
Corp., Tokyo, Japan), they were some tetra-polar family-use
models for people aged above 7 years old. For BF682, activity
level could set to levels 1 to 4, which represented different
level of physical training. And it could be set to athlete
mode to suit special needs. They defined “athlete” as a person
involved in intense physical activity of approximately 10
hours per week and who has a resting heart rate of approximately
60 beats per minutes or less (User’s Guide, TANITA Corp., Tokyo,
Japan). The results of the present study demonstrated that
there were statistically significant mean %BD differences
between these 3 BIA devices and UWW in both genders (MD = 9.43%,
9.72%, 9.29% respectively in male, MD = 9.43%, 9.72%, 9.29%
respectively in female, p < 0.05). In the scatter-plot of the
relationships between TANITA BF682, UM029 and the Ultimate
Scale with UWW (Figure 1), most of the points lied to the right
to LOI. This showed that these 3 scales overestimated %BF when
compared with UWW, as the criterion method.
For HANSON HFX50 (HANSON UK Ltd), it was a tetra-polar
household BIA scales which had “athlete mode” for determine
%BF. They defined athlete as a person who consistently trains
a minimum of three times per week for 2 hours each time, in
order to improve specific skills required in the performance
of their specific sport and/or activity (User’s Guide, HANSON
Ltd., UK). The results of the present study demonstrated that
there was a statistically significant mean % BD difference
between HANSON HFX50 and UWW in both genders (MD = 10.87% in
male, MD = 6.93% in female, p < 0.05). In the scatter-plot
of the relationships between HANSON HFX50 with UWW (Figure
1), most of the points lied to the right to LOI. This showed
that this scale overestimated %BF when compared with UWW, as
the criterion method.
For OTO WS-001 (OTO Bodycare Pte. Ltd., Singapore), it was
a tetra-polar household BIA scale for people aged 10-100. The
results of the present study demonstrated that there was a
statistically significant mean % BD difference between OTO
WS-001 and UWW in both genders (MD = 10.19% in male, MD = 3.72%
in female, p < 0.05). In the scatter-plot of the relationships
between OTO WS-001 with UWW (Figure 1), most of the points
lied to the right to LOI. This showed that this scale
overestimated %BF when compared with UWW, as the criterion
method.
For CONAIR C8991H and C8976H (CONAIR, New York, USA), they
were bi-polar BIA scales for household use for people over
16 years old. For C8891H, fitness level could be set from 1-3.
Mode one for people who exercise lightly or infrequently, like
less than 20 minutes of light aerobics one or two times a week.
Mode 2 for people engages in moderate activity for about 30
minutes, 3 to 5 times a week. Mode 3 for people who is highly
active, engaging in 60 minutes of moderate to vigorous
exercise 5 times a week (User’s Guide, CONAIR, New York, USA).
Our subjects all fit on mode 2. One of the data was missed,
as C8891H unable to detect the %BF of one lean male subject.
The results of the present study demonstrated that there were
statistically significant mean %BD differences between these
2 BIA devices and UWW in both genders (MD = 3.68%, 9.76%
respectively in male, MD = 3.77%, 2.28% respectively in female,
p < 0.05). In the scatter-plot of the relationships between
CONAIR C8991H and C8976H with UWW (Figure 2), most of the points
lied to the right to LOI. This showed that these 3 scales
overestimated %BF when compared with UWW, as the criterion
method.
For Oregon Scientific GA101 (Oregon Scientific INC., USA),
it was a 6 conductive pads household BIA scale. It could detect
people in age 7 to 99 years old (User’s Guide, Oregon Scientific
INC., USA). The results of the present study demonstrated that
there was a statistically significant mean % BD difference
between Oregon Scientific GA101 and UWW in both genders (MD
= 9.85% in male, MD = 6.33% in female, p < 0.05). In the
scatter-plot of the relationships between GA101 with UWW
(Figure 2), most of the points lied to the right to LOI. This
showed that this scale overestimated %BF when compared with
UWW, as the criterion method.
For OSIM OS-1100 (OSIM International Ltd., Singapore), it
was a tetra-polar household BIA scales for populations in 6
to 100 years old (User’s Guide, OSIM International Ltd.,
Singapore). The results of the present study demonstrated that
there was a statistically significant mean % BD difference
OSIM OS-1100 and UWW in both genders (MD = 11.45% in male,
MD = 4.77% in female, p < 0.05). In the scatter-plot of the
relationships between OS-1100 with UWW (Figure 2), most of
the points lied to the right to LOI. This showed that this
scale overestimated %BF when compared with UWW, as the
criterion method.
In this pilot study, TANITA TBF410 (TANITA Corp., Tokyo,
Japan) was not a household BIA device. And the price of it
was about twenty thousand dollars. It was out of our range
as defined “acceptable to general public”. The results were
used to compare with the others household BIA scales. The
results of the present study demonstrated that there was a
statistically significant mean % BD difference TANITA TBF410
and UWW in both genders (MD = 8.62% in male, MD = 6.07% in
female, p < 0.05). In the scatter-plot of the relationships
between TBF410 with UWW (Figure 2), most of the points lied
to the right to LOI. This showed that this scale overestimated
%BF when compared with UWW, as the criterion method. When
TBF410’s MDs are compared with that of the 3 TANITA household
BIA scales, we observed that the MD of TBF410 with UWW was
the smallest among the four TNAITA scales. But the different
was not large.
The major advantage of using these household BIA scales
to assess body composition was that the process was fast and
convenience. And it was a relatively inexpensive method to
assess %BF, and required minimum technique. However, there
were still other possible sources of error, apart from the
systematic error suggested to be present in the machines. Also,
the sources of error in present leg-to-leg BIA system were
similar to that of the conventional arm-to-leg gel-electrode
BIA system, as both types of BIA gave %BF value in correlation
with similar magnitude (Nunez, Gallagher, Visser, Pi-Sunyer,
Wang, & Heymsfield, 1997). Therefore, those household BIA
scales shared with the conventional BIA system in some similar
sources of error in measuring body composition. The major
source of error with the BIA method was intra-individual
variability in whole body electrical resistance due to factors
that affected by the participant’s hydration state (Heyward
and Stolarczyk, 1996). Eating, drinking, exercising and
dehydrating were examples of factors altering the
participant’s individual hydration state, and in turn,
affected the total body resistance and the estimated fat free
mass. Further more, there would be changes in our body
resistance, within 3.1% to 3.9% of variance attributed
day-to-day, due to the fluctuations in body water (Jackson,
Pollock, Graves, and Mahar, 1988). In present pilot study,
participants were only advised to fast 2 hours, and did not
drinks water unless they felt thirsty before the measurements
began. However, they might not follow advises and their
pre-measurement behaviors were uncontrollable. Also,
environmental factors could be another category of possible
sources of error. As Segal, Gutin, Presta, Wang and Van Itallie
(1985) realized that skin temperature would affect %BF
estimation, environment temperature was one of the factors
that affect skin temperature. Participants in present pilot
study were not measured together in one specific period within
one day. The room temperature of the laboratory might not be
the same or about the same. The number of people in the
laboratory could also affect the room temperature.
In conclusion, CONAIR C8891H had the lowest MD in males’
%BF detection, which was 3.68%. The MD of C8891H in females’
subjects was also not high, which were 3.77%. So, C8891H was
relatively more accurate in assessing %BF in our target age
group. And CONAIR C8976H had the lowest MD in females’ %BF
detection, which were 2.28%. Most of the scales were more
accurate when assessing females’ %BF, except CONAIR C8976H.
The MD in assessing female subjects was always smaller. When
analyzing the data for all the subjects, CONAIR C8891H had
the lowest MD of 3.73, which was the closest to the UWW method.
All the scales %BF values had a significant correlation with
that of UWW. And despite of the large MD between TANITA BF682
and UWW, the correlation coefficient between TANITA BF682 and
UWW (r = 0.793, p < 0.05) for all the subjects was the highest
among the 9 household BIA scales. TANITA TBF410 in the
laboratory had the highest r value (r = 0.799, p < 0.05). When
analyzing all the subject’s data, we could observe that all
the TANITA scales, CONARI C8891H and Oregon Scientific GA101
in our study had a r value higher than 7. So, in conclusion,
we could say that all TANITA BIA scales, Oregon Scientific
GA101 and CONAIR C8991H were relatively valid for assessing
%BF in Hong Kong university students (TANITA BF682: r = 0.793,
TANITA UM029: r = 0.745, TANITA Ultimate Scale: r = 0.787,
CONAIR C8991H: r = 0.735, Oregon Scientific GA101: r = 0.755,
p < 0.05).
The Criterion Method UWW
UWW was used as the criterion method for validation in the
present study. But it has been challenged on its use as a “gold
standard” since it had sources of errors for a number of reasons.
Clark et al. (1993) suggested that inaccurate measurement of
RV, lacking of ability to account for intestinal gas, the
participant’s movement in water, and variation in equipment
and methodologies were all possible errors in UWW measurement.
Katch et al. (1980) reported that a difference of 600 ml in
residual volume might affect the estimation of %BF at about
8%. Although residual volume was measured by Vmax Spirometer,
some of the subjects might had difficulties to control their
breath to fit the program’s need, and unable to check the true
residual volume.
The equation used to convert BD measured by UWW to %BF in
the present study was the one developed in 1961 by Siri. Heyward
(1996) claimed that the use of this formula or the one by Brozek
et al. (1963) was a major source of error since both of them
were derived using the 2-component body composition model and
were based on direct analysis of a limited number White male
and female cadavers who were not necessary the representative
of the entire population. Both of the equations assumed the
density of the FFB to be constant, but the density of FFB varies
with age, gender, physical activity, ethnicity, relative
proportion of water, mineral, and protein comprising the FFB.
The average density of the FFB for some population groups might
be close to the assumed value (1.10 g/cc), but
inter-individual variations of a high degree might present.
Heyward (1996) claimed that it is necessary for “using body
composition prediction equations that are validated against
a reference body composition measure derived from
multi-component models and a combination of technologies that
account for individual differences in bone mineral content
and hydration levels” (p. 150). Besides, UWW also required
much cooperation from the participants. Participants who were
afraid of being totally submerged in the water might not be
able to expel the air in their lungs, even to an acceptable
amount.
Chapter 5
SUMMARY AND CONCLUSION
The present study attempted to determine the validity of
9 common BIA analyzers which could be bought in most local
department stores. It included the following models: TANITA,
CONAIR, OTO, OSIM, HANSON, and Oregon Scientific, and the cost
ranged between HK$399 and HK$895, which could be afforded by
general public. In this study, we would like to use these nine
different models of leg-to-leg BIA devices, and compare the
results got from UWW.
Summary of Results
The present study showed that the %BF values produced by
CONAIR C8891H had the lowest mean difference (MD) in males’
%BF detection, which is 3.68%. The MD of CONAIR C8891H in
females’ subjects was also low, which are 3.77%. All the scales
%BF values had significant correlations with that of UWW. And
despite of the large MD between TANITA BF682 and UWW, the
correlation coefficient between TANITA BF682 and UWW (r =
0.793, p < 0.05) for all the subjects is the highest among
the 9 household BIA scales. TANITA TBF410 in the laboratory
have the highest r value (r = 0.799, p < 0.05). When analyzing
the entire subject’s data, we could observe that all the TANITA
scales, CONAIR C8891H and Oregon Scientific GA101 in our study
had r values higher than 0.7, which was accepted as a valid
tool to assess %BF (p < 0.05).
Conclusions
Using underwater weighing as a criterion method, the 9
different models of leg-to-leg household BIA scales were valid
in assessing body composition. Most of the scales gave closer
%BF value to that of UWW method when assessing females’ %BF,
except CONAIR C8976H. The MD in assessing female subjects was
always smaller. When analyzing the data for all the subjects,
CONAIR C8891H had the lowest MD of 3.73, which was the closest
to the UWW method. So, C8891H was relatively more accurate
in assessing %BF in our target age group. So we could say that
CONAIR C8891H is a relatively more valid household BIA scale
in our pilot study (r = 0.735, MD = 3.73) when compared with
UWW method to assess %BF. In conclusion, we could say that
all TANITA BIA scales, Oregon Scientific GA101 and CONAIR
C8991H were relatively valid for assessing %BF in Hong Kong
university students (TANITA BF682: r = 0.793, TANITA UM029:
r = 0.745, TANITA Ultimate Scale: r = 0.787, CONAIR C8991H:
r = 0.735, Oregon Scientific GA101: r = 0.755, p < 0.05).
Recommendations
The use of an accurate and reliable criterion method is
vital in validation studies. Estimation of body density by
UWW based on the 2-component model did not involve a number
of demerits as discussed in the previous chapters. A better
body composition model should be chose. It could improve the
accuracy of body composition assessment by UWW. Some of the
subjects were fear of deep water. It would affect the UWW
procedures. Dual-energy x-ray absorptiometry (DEXA) was a
better criterion method, which could detect all the body
composition in the subject’s body on land. And they need not
to submerge in water. But the equipments were very expensive
and not available in the laboratory
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APPENDIX A
Consent From to Participants
Hong Kong Baptist University
Informed Consent for Body Composition Analysis
In order to assess the body composition of the Chinese university adults for the purpose of validating various Bioelectrical Impedance Analysis (BIA) analyzers against the underwater weighing (UWW) method, the undersigned hereby voluntarily consents to involve in the measurements of the BIA devices, residual volume and UWW. Explanation of the Tests The measurement of percentage body fat using the BIA devices requires the participant to stand in an upright position on the footpad electrodes of the monitors. Residual volume measurement procedure involves panting, maximal inhalation and exhalation in a gas chamber. Data obtained by the program will be used for percentage body fat calculation in UWW. The UWW procedure involves the participant being completely submerged in a warm water tank and expires maximally. This test provides the participant an accurate assessment of body composition. Risk and Discomforts BIA devices and residual volume measurement procedures are very safe and there is generally no risk and discomforts during the procedures. Participant may experience some discomforts during the UWW procedure, especially if the precipitant is fearful of being submerged. Detailed instruction by the test administrators and plenty of practices will be given to the participant to minimize the discomforts. Inquires Questions about the detailed procedures of the analysis are encouraged. If the participant has any questions or needs additional information, please ask the test administrator to explain further.
Freedom of Consent The participant’s permission to participate is voluntary and the participant is free to stop the test at any point, if he or she so desires. In signing this consent from, I, (Name of Participant), affirm that I have read this form in its entirety and that I understand the description of the testing procedures and the risks and discomforts, and having had an opportunity to ask questions that have been answered to my satisfaction. (Signature of participant) (Date) (Person administering tests) (Date)
APPENDIX B
Data Collection Form
Hong Kong Baptist University
Body Composition Analysis: Data Collection Form
Name: Student ID: Age: Sex: Weight: (kg) Height: (cm) Tester(s): BMI: Underwater Weighting Residual Volume Water Temp.: ℃ Trail 1: Chair Weight: g Trail 2: Trail 1: Trail 3: Trail 2: Trail 4: Trail 3: Trail 5: Trail 4: Trail 5: Trail 6: Trail 7: Trail 8: Trail 9: Trail 10: BIA data C: kg %BF 1: kg %BF 6: kg %BF 2: kg %BF 7: kg %BF 3: kg %BF 8: kg %BF 4: kg %BF 9: kg %BF 5: kg %BF
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