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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


UWW in female participants.......................37


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




Methods when compared with UWW in female

subjects........................................43




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


Relative Body Fat (%BF)

The FM expressed as a percentage of total body weight


Essential Lipids

Compound lipids (phospholipids) needed for cell membrane

formation, consists of about 10% of total-body lipid (Heyward


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


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


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


OSIM OS1100 30 0.398* 0.030

TANITA TBF410 30 0.648** 0.000


* 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


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


OSIM OS1100 58 0.535** 0.00

TANITA TBF410 58 0.799** 0.00


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



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



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


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


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


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


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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