J.Anthrop.Soc.Nippon人 類 誌 99(2):141-148(1991) Body Composition and Lean Body Mass Index for Japanese College Students Komei HATTORI Laboratory of Anatomy and Physical Activity Sciences, College of General Education, Ibaraki University Abstract Lean body mass (LBM) and fat mass (FM) are two major components of body composition and when totalled equal body mass. Body mass index (BMI) as represented by weight/height2, has proven to be both a simple and valid way of assessing body composition. However, the significance of the index is not clear since body weight is composed of two main components: LBM and FM, each of whose densities show distinct differences. In order to present the body constitution as clear quantitative measures, the lean body mass index (LBMI; LBM/height2), fat mass index (FMI; FM/height2) and a chart system (body composition chart) are introduced in this study. Through this chart system, we can detect the relative amount of the two major body constructs and differentiate subjects into adipo-muscular, lean-muscular, adipo-atrophy and lean- atrophy types. Keywords Body composition, Lean body mass index, Japanese, Students TREMBLAY, 1990; WATSON,1984). As a simple Introduction indicator of body composition, body mass index, Lean body mass (LBM) and fat mass (FM) are as represented by weight/height2, has prevailed two major components of body composition and due to its validity (BILLEwICZ et al., 1962; EL- when totalled equal body mass. The proportion NOFELY, 1986; FLOREY, 1970; GARN and of the two components is of great concern in the PESICK, 1982; KEYS et al., 1972; KHOSLA and fields of human biology, clinical medicine and LOWE,1967; MIcozzI et al., 1986; REVICKIand exercise physiology because it is an important ISRAEL, 1986; ROSS et al. 1988; SMALLEY et anthropological indicator (ABDEL-MALEKet al., al., 1990; WOMERSLEY et al., 1976). However, 1985; BENN, 1971; HARSHA et al., 1980; the significance of the index is still not clear since MUELLER, 1982; VAGUE, 1956) and an indicator body weight is composed of two main com- of chronic disease risk factors (DEUTCH and ponents: LBM and FM whose densities each MUELLER, 1985; FREEDMAN, 1987, 1989). In show distinct differences. The body mass index addition it is also related to habitual physical (BMI) is generally accepted as reflecting excess activity (BROWN, 1977; SATWANTI et al., 1983; fat, but it also shows the reverse information. Article No. 9105 Received February 7, 1991 142 K. HATTORI That is, the greater one's BMI value the greater weight/height2 index was used in this paper proportion of lean body mass such as muscle or because it has been recommended by many bone (WOMERSLEY and DURNIN, 1977). authors as a valid estimate of body fat which is SMALLEY et al. (1990) have also suggested that also independent of height (KEYS et al., 1972; BMI should be used with caution as an indicator HATTORI et al., 1977; REVICKI and ISRAEL, of obesity. 1986; MICOZZI et al., 1986). Body mass index For an analysis of the gross body constitution, can be divided into two terms as follows: the somatotype method may be useful, provided BMI = weight/height2 only general information about physique or = (LBM + FM)/height2 physical constitution is required. Since the basic = LBM/height2 + FM/height2 idea of the somatotype method is qualitative (in The two indices that compose of BMI; spite of its scoring system), quantitative informa- LBM/height2 and FM/height2 are termed lean tion about fat and LBM are not revealed by this body mass index (LBMI) and fat mass index method. (FMI), respectively. To present body constitution in clear Results quantitative measures, the lean body mass index (LBMI), fat mass index (FMI) and a chart system The data on body composition are shown in are introduced in this paper. Table 1. The means for LBM and FM were 51.3 kg and 9.0 kg for males, and 38.9 kg and 11.9 Subjects and Methods kg for females. Males tended to have a larger Subjects were 67 male and 76 female college amount of LBM and smaller amount of FM than students ranging in age from 18 to 22 years. All females in terms of absolute values. It should be were in average health and none were engaged stressed that BMI values for both sexes did not in special exercise programs. Body density was show a large difference (20.9 for males and 20.4 determined by hydrostatic weighing with residual for females). However, mean LBMI for males lung volume calculated by the O2 rebreathing was larger than that for females (17.8 and 15.6). method (WILMORE et al. 1980). LBM and FM Conversely, mean FMI for females was larger were calculated by SIRI's equation (SIRI, 1956). than that for males (4.8 and 3.1). While other studies of body composition of the Percent body fat is generally used as the Japanese have employed BROZEK's equation criterion for adiposity level. The relationship (NAGAMINE and SUZUKI, 1964; OHNAKA, between percent fat and FMI is shown in Fig. l . 1986), the SIRI equation was used in this study Since the two items showed clear correlations because of its theoretical simplicity and ease of (0.97 for males and 0.95 for females), the modification when the subject's LBM and fat significance of the information from FMI is densities differ from the adult standard almost identical with that from percent fat. (LOHMAN,1986). In practice both equations are Figs. 2 and 3 are scatter graphs for LBMI and based on similar densitometric data of various FMI vs. stature. No significant correlations were tissues. Since the data are a relatively constant found between the two items in both sexes. Thus biological factor, it was felt that SIRI's equation the two indices appear to be independent of body could equally well be applied to a Japanese size. Therefore, graphically the position in the sample (HATTORI et al., 1991). chart that the two indices take, given one com- Of the various body mass indices, ponent on each axis, represent the subject's status Lean Body Mass Index for Japanese 143 Table 1. Body composition and body mass indices for males and females ** Significant sex difference at p< .01 Fig. 1. Scatter plot of percent body fat (% Fat) vs. fat mass index (FM/height2), on the two components independent of size. + SD are termed atrophy, intermediate and Tables 2 and 3 show the dividing points of LBMI muscular for LBMI, and lean, intermediate and and FMI based on the mean values and standard adipose for FMI. Figs. 4 and 5 represent the deviations. The groups below the mean-SD, body composition chart for males and females. between means ± SDs and larger than mean The subjects located in the upper right section Table 2. Categorization of muscularity based on lean Table 3. Categorization of adiposity based on fat mass body mass index index 144 K. HATTORI Fig. 2. Scatter plot of stature vs. lean body mass index (LBM/height2).Fat mass index Fig. 3. Scatter plot of stature vs. fat mass index. have somewhat larger amounts of fat and LBM male and two female subjects in these sections. (adipo-muscular). Three subjects of each sex Fig. 6 presents the distribution of intermediate belong to this category. The lower right section subjects for both males and females. The male corresponds to a lean-muscular physique. Only intermediate zone is shifted toward the muscular one female subject is in this section. Upper left and lean sides of the female on the LBMI and and lower left sections are termed the adipo- FMI axes. atrophy and lean atrophy sections. There are four Lean Body Mass Index for Japanese 145 Body Composition Chart MatesFat Mass Index Lean Body Mass Index Fig. 4. Body composition chart for males. Lean body mass index and fat mass index are classified into three subgroups, respectively. Body Composition Chart FemalesFat mass index Lean Body Mass Index Fig. 5. Body composition chart for females. Lean body mass index and fat mass index are classified into three subgroups, respectively. 146 K. HATTORIFat Mass Index Lean Body Mass Index Fig. 6. Average distribution of two indices for both sexes in the body com- position chart. tailed information on body composition that is Discussion not necessarily clear in traditional analytical pro- Several reports have concluded that total body cedures. The body composition chart system may adiposity does not show a significant correlation be persuasive in practical assessment situations with body height (FLEGAL, 1990; GARN and because of its visual representation style. This in- PESICK, 1982; FRISANCHO and FLEGAL, 1982; formation is typically important since many MICOzzI et al., 1986; REVICKI and ISRAEL, people attempt to lose weight without any interest 1986; WOMERSLEY and DURNIN, 1977; HIMES or concern for body composition. Following the and ROCHE, 1986). In this sense, fat mass is weight reduction, however, LBM is atrophied and adequate to indicate total body adiposity. percent fat increased or maintained unless the However, it cannot be denied that fat mass is in- person adds an exercise regimen. Using the body fluenced by many factors, body size being one composition chart system, we can distinguish latent factor. Hence the percent fat (proportion those who are slim without excess fat from the of fat mass vs. body mass) is verified as a proper slim who maintain fat or so called "hidden indicator of adiposity. It therefore seems obesity". reasonable to assess adiposity by FMI since the two indices are strongly correlated. Acknowledgment One of the advantages of using LBMI and The author is grateful to Dr.