VALIDITY OF VARIOUS BIOELECTICAL IMPEDANCE ANALYSIS (BIA) ANALYZERS IN ASSESSING BODY FATNESS AMONG HONG KONG UNIVERSITY STUDENTS

Transcription

1 VALIDITY OF VARIOUS BIOELECTICAL IMPEDANCE ANALYSIS (BIA) ANALYZERS IN ASSESSING BODY FATNESS AMONG HONG KONG UNIVERSITY STUDENTS BY CHAN YIU WA 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

2 15 th 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 Chief Advisor Prof. B. Chow Second Reader Process Grade: Product Grade: Overall Grade:

3 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:

4 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.

5 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 REVIEW OF LITERATURE...11 Underwater Weighing (UWW) Bioelectrical Impedance Analysis (BIA) Summary METHODOLOGY...27 Subjects Body Height and Weight Measurements BIA Measurements UWW Measurement Determination of Residual Volume... 30

6 CHAPTER Page Method of Analysis ANALYSIS OF DATA...33 Results Discussion SUMMARY AND CONCLUSIONS...63 Summary of Results Conclusions Recommendations BIBLIOGRAPHY...66 APPENDICES...70 A. Consent From to Participants B. Data Collection Form... 72

7 LIST OF TABLES TABLE Page 1. Physical Characteristics of the male Participants (N = 30) Physical Characteristics of the female Participants (N = 30) Correlation of the %BF results from BIA devices with UWW in male participants Correlation of the %BF results from BIA devices with UWW in female participants Correlation of the %BF results from BIA devices with UWW for all participants 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

8 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 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

9 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) 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

10 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

11 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

12 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

13 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).

14 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).

15 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

16 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).

17 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.

18 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 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

19 for Chinese population.

20 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, 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

21 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

22 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 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

23 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 g/cc, and the density of the FFB was assumed to be 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

24 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).

25 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

26 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 = M A / {M A M W (RV 100) WD} Where M A was the mass of body in air in g, M W 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

27 by a force transducers (Going, 1996). The underwater weighing system originally described by Goldman and Buskirk in 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

28 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

29 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

30 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

31 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

32 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.

33 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

34 jogging and cycling at moderate intensities (~70% VO 2 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

35 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.

36 Chapter 3 METHODOLOGY Subjects Thirty Chinese male and thirty Chinese female university students, aged 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

37 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

38 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 o C. 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

39 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 D L 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

40 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

41 %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.

42 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 ±1.26 Weight(kg) ±8.85 Height(cm) ±6.98 BMI ±2.21 RV(L) ±0.35 Table 2 Physical Characteristics of the female Participants (N = 30) Minimum Maximum Mean ±SD age ±1.4 Weight(kg) ±5.49 Height(cm) ±4.14 BMI ±1.82 RV(L) ±0.25 The age of the male participants were ranged from years old with a mean age of 21 years old and a standard deviation

43 of 1.26 years. The age of the female participants were ranged from years old with a mean age of years old and a standard deviation of 1.40 years. The weights of the male participants were ranged from kg with a mean weight of kg and a standard deviation of 8.85 kg. The weights of the female participants were ranged from kg with a mean weight of kg and a standard deviation of 5.49 kg. The heights of the male participants were ranged from cm with a mean height of cm and a standard deviation of 6.98 cm. The heights of the female participants were ranged from cm with a mean height of cm and a standard deviation of 4.14 cm. The BMI of the male participants were ranged from with a mean BMI of and a standard deviation of The BMI of the female participants were ranged from with a mean BMI of and a standard deviation of 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

44 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.

45 Table 3 Correlation of the %BF results from BIA devices with UWW in male participants BIA models n r p TANITA BF ** TANITA UM ** TANITA ULTIMATE SCALE ** HANSON HFX ** OTO WS ** CONAIR C8991H ** CONAIR C8976H ** Oregon Scientific GA ** OSIM OS ** TANITA TBF ** **Correlation is significant at the 0.01 level (2-tailed).

46 Table 4 Correlation of the %BF results from BIA devices with UWW in female participants BIA models n r p TANITA BF ** TANITA UM ** TANITA ULTIMATE SCALE ** HANSON HFX ** OTO WS * CONAIR C8991H * CONAIR C8976H ** Oregon Scientific GA ** OSIM OS * TANITA TBF ** **Correlation is significant at the 0.01 level (2-tailed). * Correlation is significant at the 0.05 level (2-tailed).

47 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 in male, where the value in female was For the correlation coefficients between UWW and TANITA UM029, the Pearson correlation value was in male, as the value in female was For TANITA Ultimate Scale, the Pearson correlation with UWW was in male, and female was These three TANITA BIA devices, with TANITA TBF410, where the values were and 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 in male, and in female. OTO WS001 had values of

48 0.564 and in males and females respectively. CONAIR C8991H and CONAIR C8976H had r value at and for male, and and for female respectively. CONAIR C8891H gave the highest p value, 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 and Lastly, for OSIM OS1100, r value in male was 0.530, and in female was OSIM OS1100 had the highest p value in female participants, which was 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 to 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.

49 Table 5 Correlation of the %BF results from BIA devices with UWW for all participants BIA models n r p TANITA BF ** 0.00 TANITA UM ** 0.00 TANITA ULTIMATE SCALE ** 0.00 HANSON HFX ** 0.00 OTO WS ** 0.00 CONAIR C8991H ** 0.00 CONAIR C8976H ** 0.00 Oregon Scientific GA ** 0.00 OSIM OS ** 0.00 TANITA TBF ** 0.00 **Correlation is significant at the 0.01 level (2-tailed).

50 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.

51 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 ±4.04 / / / / TANITA BF ± TANITA UM ± TANITA Ultimate Scale ± HANSON HFX ± OTO WS ± CONAIR C8991H ± CONAIR C8976H ± Oregon Scientific GA ± OSIM OS ± TANITA TBF ±

52 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 ±5.37 / / / / TANITA BF ± TANITA UM ± TANITA Ultimate Scale ± HANSON HFX ± OTO WS ± CONAIR C8991H ± CONAIR C8976H ± Oregon Scientific GA ± OSIM OS ± TANITA TBF ±

53 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 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 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 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 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

54 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, 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 ± 3.67, ± 3.74, ± 3.71, and ± 3.49 respectively. In female subjects, the Mean ± SD values were ± 3.89, ± 3.81, ± 3.85, and ± 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 ± 3.96, and ± 4.54 respectively. In female subjects, the Mean ± SD values were ± 3.49, and ± 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.

55 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 ±6.41 / / / / TANITA BF ± TANITA UM ± TANITA Ultimate Scale ± HANSON HFX ± OTO WS ± CONAIR C8991H ± CONAIR C8976H ± Oregon Scientific GA ± OSIM OS ± TANITA TBF ±

56 The mean ± standard deviation and MD for all subjects were shown in Table 8. TANITA BF-682 (mean ± SD = ± 4.82, MD = 8.09), TANITA UM-029 (mean ± SD = ± 4.62,MD = 8.06), TANITA Ultimate Scale (mean ± SD = ± 4.79,MD = 7.90), HANSON HFX50 (mean ± SD = ± 4.98,MD = 8.83), OTO WS-001 (mean ± SD = ± 4.53,MD = 6.84), CONAIR C8991H (mean ± SD = ± 5.68,MD = 3.73), CONAIR C8976H (mean ± SD = ± 4.40,MD = 5.89), Oregon Scientific GA101 (mean ± SD = ± 4.47,MD = 8.03), OSIM OS-1100 (mean ± SD = ± 2.90,MD = 7.99) and TANITA TBF410 (mean ± SD = ± 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 < Figure 1 and 2 showed the relationships of %BF values between UWW and the BIA devices for all subjects.

57 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) UWW (%BF) UWW (%BF) LOI 5.00 LOI TANITA_BF682 (%BF) TANITA_UM029 (%BF) UWW (%BF) UWW (%BF) LOI 5.00 LOI TANITA_UltimateScale (%BF) HANSON_HFX50 (%BF) UWW (%BF) LOI OTO_WS001 (%BF) LOI = Line of identity

58 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) UWW (%BF) UWW (%BF) LOI 5.00 LOI CONAIR_C8991H (%BF) CONAIR_C8976H (%BF) UWW (%BF) UWW (%BF) LOI 5.00 LOI Oregon_Scientific_GA101 (%BF) OSIM_OS1100 (%BF) UWW (%BF) LOI TANITA_TBF410 (%BF) LOI = Line of identity

59 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 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.

60 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 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 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

61 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%,