The use of body mass index to predict body composition in children

Background : Simple anthropometric indices of body composition have particular appeal for use in children, and as such body mass index (BMI) has been used to predict percentage body fat in a number of studies. Aim : To evaluate the relationship between BMI and percentage body fat (%body fat) and a proposed, more appropriate relationship between BMI and fat mass/height 2 in a cohort of young children. Subjects and methods : Cross-sectional study of 109 children aged between 6 and 10 years residing in either Sydney or Brisbane, Australia. Weight and height were measured using standard methods. Body composition was measured using a stable isotope method to firstly determine total body water and subsequently fat free mass. Results : The correlation between BMI and fat mass/height 2 was markedly greater than that between BMI and percentage body fat. In the entire group of children the R 2 ( &#50 100%) value for the relationship between BMI and fat mass/height 2 was 73.3% compared with 46.5% for the relationship between BMI and percentage body fat. Conclusions : We have shown that the use of BMI to predict fat mass/height 2, and consequently percentage body fat, is superior to the use of BMI to predict percentage body fat based directly upon the R 2 values of the above analysis.     

The use of body mass index to predict body composition in children

BACKGROUND: Simple anthropometric indices of body composition have particular appeal for use in children, and as such body mass index (BMI) has been used to predict percentage body fat in a number of studies. AIM: To evaluate the relationship between BMI and percentage body fat (%body fat) and a proposed, more appropriate relationship between BMI and fat mass/height(2) in a cohort of young children. SUBJECTS AND METHODS: Cross-sectional study of 109 children aged between 6 and 10 years residing in either Sydney or Brisbane, Australia. Weight and height were measured using standard methods. Body composition was measured using a stable isotope method to firstly determine total body water and subsequently fat free mass. RESULTS: The correlation between BMI and fat mass/height(2) was markedly greater than that between BMI and percentage body fat. In the entire group of children the R(2) (x100%) value for the relationship between BMI and fat mass/height(2) was 73.3% compared with 46.5% for the relationship between BMI and percentage body fat. CONCLUSIONS: We have shown that the use of BMI to predict fat mass/height(2), and consequently percentage body fat, is superior to the use of BMI to predict percentage body fat based directly upon the R(2) values of the above analysis.     

Body mass index and the prediction of percentage body fat in Australian Chinese women

Background: Body mass index (BMI) is frequently related to percentage body fat. Nevertheless, the relationship between BMI and fat mass/height² (FM/H²), theoretically, should be more appropriate.

Aim: This study seeks to evaluate the relationship between BMI and both percentage body fat and FM/H² in a group of Chinese Australian females.

Subjects and methods: Forty subjects took part in the study and all were Chinese females resident in Brisbane, Australia. Body mass index was calculated from height and weight. Percentage body fat and fat mass were calculated from measurements of total body water.

Results: The use of BMI to predict FM/H² accounted for double the variance of that found when BMI was used to predict percentage body fat.

Conclusions: As a consequence, it is possible that the use of BMI to predict FM/H² and not percentage body fat in the first instance may prove to be more useful in a number of adult populations. Nevertheless, with a relatively small sample size it is difficult, if not impossible, to test the developed equations on a validation group and further investigation into the findings described in this paper needs to be undertaken.

Hintergrund: Der Body Mass Index (BMI) wird häufig mit dem prozentualen Körperfett in Verbindung gebracht. Jedoch erscheint das Verhältnis zwischen BMI und Fettmasse/Körpergröße² (FM/H²) theoretisch angemessener zu sein. Ziel: Diese Studie versucht, sowohl das Verhältnis zwischen BMI und prozentualem Körperfett als auch FM/H² in einer Gruppe von australischen Frauen chinesischer Abstammung auszuwerten. Material und Methoden: Vierzig Frauen chinesischer Abstammung, die in Brisbane (Australien) ansässig waren nahmen an der Studie teil. Der BMI wurde aus Körpergröße und Gewicht errechnet. Das prozentuale Körperfett und die Fettmasse wurden anhand von Messungen des Gesamtkörperwassers errechnet. Ergebnisse: Bei der Verwendung des BMI zur Bestimmung von FM/H² kommt es zu einer Verdopplung der Varianz gegenüber der Verwendung des BMI zur Vorhersage des prozentualen Körperfettes. Schlußfolgerungen: Es ist möglich, daß bei einer Vielzahl von Erwachsen die Verwendung des BMI zur Vorhersage von FM/H² nützlicher sein kann als zur Bestimmung des prozentualen Körperfettes. Es ist jedoch schwierig, wenn nicht sogar unmöglich, anhand der verhältnismäßig kleinen Stichprobe die entwickelten Gleichungen zu prüfen. Es sollten weitere Untersuchungen im Hinblick auf die hier gemachten Befunde erfolgen.

Contexte: L'indice de masse corporelle (IMC) est fréquemment associé au pourcentage de graisse corporelle, cependant la relation entre IMC et masse grasse/stature² (MG/H²) serait théoriquement plus appropriée. But: cette étude cherche à évaluer la relation entre l'IMC, le pourcentage de graisse corporelle ainsi que MG/H² dans un groupe de femmes australiennes d'origine chinoise. Matériel et méthode: quarante chinoises résidentes à Brisbane en Australie, ont pris part à l'étude. L'indice de masse corporelle a été calculé à partir du poids et de la stature. Le pourcentage de graisse et la masse grasse l'ont été à partir de mesures de l'eau corporelle totale. Résultats: l'utilisation de l'IMC pour prédire MG/H² fournit une variance double de celle qui est trouvée lorsque l'IMC est utilisé pour prédire le pourcentage de graisse corporelle. Conclusions: en conséquence, il est possible que l'utilisation de l'IMC pour prédire MG/H² et non le pourcentage de graisse corporelle se révèle plus utile pour nombre de populations adultes. Cependant, il est difficile sinon impossible d'éprouver les équations développées sur un groupe de validation à partir d'un échantillon de taille relativement faible, si bien que d'autres recherches sur les résultats présentés dans ce travail doivent être effectuées.     

Age‐related pattern of body density and body composition of Japanese men and women 18–59 years of age

Age‐related patterns of body size and composition were studied in a cross‐sectional sample of Japanese adults 18–59 years of age. Height, weight, the body mass index (BMI), body density (BD), percentage body fat (%Fat), fat mass (FM), fat‐free mass (FFM), and the sum of seven skinfold thicknesses (SF) of 288 men and 552 women were considered. Body density was measured by underwater weighing densitometry. Mean values of height, weight, BMI, BD, %Fat, FM, FFM, and SF of males were 169.0 cm, 65.3 kg, 22.8 kg/m², 1.0600 g/ml, 17.0%, 11.4 kg, 53.9 kg, and 95.0 mm, respectively, while corresponding values for females were 157.4 cm, 52.9 kg, 21.4 kg/m², 1.0420 g/ml, 24.4%, 13.1 kg, 39.7 kg, and 128.2 mm, respectively. Height, BD, and FFM correlated negatively with age in both sexes, while weight, BMI, %Fat, FM, and SF correlated positively with age. The highest BD and the lowest %Fat were observed in males ages 20 to <25 years (G20) and in females 25 to <30 years (G25). The lowest BD and highest %Fat were observed in G50 in both sexes. Correlations among parameters of body size and composition were stable with age in each sex. Height correlated negatively with BMI and %Fat in females, but not in males. In males, FM started to increase between G20 and G25 and continued to increase until G50, while SF and BMI remained stable during this period. In females, FM accumulation started around 30 years of age and continued until G50 and was accompanied by increases in SF and BMI. Am. J. Hum. Biol. 14:743–752, 2002. © 2002 Wiley‐Liss, Inc.     

Validity of BMI as a measure of obesity in Australian white Caucasian and Australian Sri Lankan children

BACKGROUND: Body mass index (BMI) is used to diagnose obesity. However, its ability to predict the percentage fat mass (%FM) reliably is doubtful. Therefore validity of BMI as a diagnostic tool of obesity is questioned. AIM: This study is focused on determining the ability of BMI-based cut-off values in diagnosing obesity among Australian children of white Caucasian and Sri Lankan origin. SUBJECTS AND METHODS: Height and weight was measured and BMI (W/H2) calculated. Total body water was determined by deuterium dilution technique and fat free mass and hence fat mass derived using age- and gender-specific constants. A %FM of 30% for girls and 20% for boys was considered as the criterion cut-off level for obesity. BMI-based obesity cut-offs described by the International Obesity Task Force (IOTF), CDC/NCHS centile charts and BMI-Z were validated against the criterion method. RESULTS: There were 96 white Caucasian and 42 Sri Lankan children. Of the white Caucasians, 19 (36%) girls and 29 (66%) boys, and of the Sri Lankans 7 (46%) girls and 16 (63%) boys, were obese based on %FM. The FM and BMI were closely associated in both Caucasians (r=0.81, P<0.001) and Sri Lankans (r=0.92, P<0.001). Percentage FM and BMI also had a lower but significant association. Obesity cut-off values recommended by IOTF failed to detect a single case of obesity in either group. However, NCHS and BMI-Z cut-offs detected cases of obesity with low sensitivity. CONCLUSIONS: BMI is a poor indicator of percentage fat and the commonly used cut-off values were not sensitive enough to detect cases of childhood obesity in this study. In order to improve the diagnosis of obesity, either BMI cut-off values should be revised to increase the sensitivity or the possibility of using other indirect methods of estimating the %FM should be explored.     

Age‐related pattern of body density and body composition in Japanese males and females, 11 and 18 years of age

The age‐related pattern of body density and body composition in Japanese males (n = 266) and females (n = 318), 11.00 to 18.99 years of age was studied. Body density (BD) as well as height, body weight, and seven skinfold thicknesses were measured. Percentage fat (%Fat) was calculated using the age‐ and sex‐specific equation of Lohman. Fat mass (FM), fat‐free mass (FFM), and the body mass index (BMI) were calculated. The trend for BD in males was lowest at 11 years (1.0530 g/ml) and increased to 1.0695 g/ml at 14 years, and then decreased slightly at 15 to 17 years. In female, BD decreased from 1.0530 g/ml at 13 years to 1.0424 g/ml at 17 years. Mean %Fat was highest in males at 11 years (15.8%), and lowest at 14 years (10.1%). The highest mean %Fat in females occurred at 16 years (22.8%), and the lowest at age 11 years (15.2%). Overall, only 6.8% of males and 3.1% of females were classified as obese. Between 11 and 18 years, FFM of males differed by 20.7 kg or 67.9%, whereas females showed a difference of only 10.8 kg or 34.7%. Consequently, age effects explained approximately 60% of the male variance of FFM but only 26% in females. Body density of each sex and age group in this study did not differ significantly from previous Japanese studies, and the pooled BD data for 1,457 Japanese including the present study are reported as a reference. Am. J. Hum. Biol. 14:327–337, 2002. © 2002 Wiley‐Liss, Inc.     

Lean body mass and bone mineral density in physically exercising postmenopausal women

OBJECTIVES: To investigate whether the relative contribution of body composition (lean and fat mass component) to postmenopausal bone mineral density (BMD) differs between women participating in physical exercise and sedentary women. METHODS: Subjects were 45 postmenopausal women participating in regular physical exercise and 89 sedentary controls aged 50-60 years. Baseline characteristics included age, height, weight, body mass index (BMI, Wt/Ht(2)), age at menopause, and years since menopause (YSM). Body fat mass, percentage of body fat, lean body mass, and lumbar spine BMD (L2-4) were measured by dual-energy X-ray absorptiometry. RESULTS: Although age, height, weight, BMI, and YSM did not differ between the two groups, lean body mass and lumbar spine BMD were significantly higher (P<0.05 and <0.001, respectively), while body fat mass and percentage of body fat mass were significantly lower in exercising women than in sedentary controls (P<0.05 and <0.05, respectively). In exercising women, BMD was positively correlated with lean body mass (r=0.415, P<0.01) but not with body fat mass (r=0.155, NS). Conversely, in sedentary controls, BMD was correlated with body fat mass (r=0.251, P<0.05) and lean body mass (r=0.228, P<0.05). CONCLUSIONS: Lean body mass is a more significant determinant of postmenopausal BMD in physically exercising women than in sedentary women.     

Why is the body mass index calculated as mass/height2, not as mass/height3?

BACKGROUND: The body mass index or BMI, mass/height(2), is used to predict fatness and health. It is an approximation to the Benn index, mass/height(p), where p (typically 1.1-2.5 for adult populations) makes the index uncorrelated with height. Mass/height(3) is an index of body build that is independent of scale and statistics. AIM: To explain why p varies and is less than three, show how statistical methods can distort perceptions of mass-height relationships, and clarify the nature of the BMI. METHODS: A hypothetical adult population is modelled statistically, with mass being approximately proportional to height(3) and with neither variable determining the other. Values of p are calculated both for the model and for real adults. RESULTS: In both cases p increases with the correlation between mass and height. Both p and that correlation are usually lower for women than for men. CONCLUSIONS: In adult populations mass must vary more nearly with height(3) than with height(2), although, for reasons explained, conventional statistical techniques suggest otherwise. Nevertheless the BMI is a valid predictor of fatness from mass and height in adults and is properly divisible into fat mass and fat-free mass indices. The validity of the latter three indices for children is questionable.     

Fat mass and fat-free mass as indicators of body composition among Bengalee Muslim children

Background: The composition of fat mass (FM) and fat-free mass (FFM) are now considered to be important indicators of body composition.

Aim: This cross-sectional study determines the body composition using FM and FFM among children.

Subjects and methods: The study was conducted among 1248 children (619 boys; 629 girls) aged 5–12 years and belonging to the Bengalee Muslim population of West Bengal, India. Anthropometric measurements of height, weight, triceps and sub-scapular skin-folds were recorded and body mass index (BMI) calculated. Body composition was assessed using FM and FFM.

Results: The age-specific mean values of FM and FFM ranged from 1.93–3.07 kg (boys) and 1.91–3.62 kg (girls) and from 14.69–23.44 kg (boys) and 14.18–22.87 kg (girls), respectively. Statistically significant sex differences were observed in FM and FFM (p < 0.05). Age- and sex-specific smooth percentile curves were derived for BMI, FM and FFM using the L, M and S modelling approach for further evaluation of body composition.

Conclusion: These findings are important for future investigations in the field and in epidemiological and clinical settings so as to accurately identify risk of lower or higher adiposity and body composition using FM and FFM.     

Validity of BMI as a measure of obesity in Australian white Caucasian and Australian Sri Lankan children

Background: Body mass index (BMI) is used to diagnose obesity. However, its ability to predict the percentage fat mass (%FM) reliably is doubtful. Therefore validity of BMI as a diagnostic tool of obesity is questioned. Aim: This study is focused on determining the ability of BMI-based cut-off values in diagnosing obesity among Australian children of white Caucasian and Sri Lankan origin. Subjects and methods: Height and weight was measured and BMI (W/H²) calculated. Total body water was determined by deuterium dilution technique and fat free mass and hence fat mass derived using age- and gender-specific constants. A %FM of 30% for girls and 20% for boys was considered as the criterion cut-off level for obesity. BMI-based obesity cut-offs described by the International Obesity Task Force (IOTF), CDC/NCHS centile charts and BMI-Z were validated against the criterion method. Results: There were 96 white Caucasian and 42 Sri Lankan children. Of the white Caucasians, 19 (36%) girls and 29 (66%) boys, and of the Sri Lankans 7 (46%) girls and 16 (63%) boys, were obese based on %FM. The FM and BMI were closely associated in both Caucasians (r?=?0.81, P<0.001) and Sri Lankans (r?=?0.92, P<0.001). Percentage FM and BMI also had a lower but significant association. Obesity cut-off values recommended by IOTF failed to detect a single case of obesity in either group. However, NCHS and BMI-Z cut-offs detected cases of obesity with low sensitivity. Conclusions: BMI is a poor indicator of percentage fat and the commonly used cut-off values were not sensitive enough to detect cases of childhood obesity in this study. In order to improve the diagnosis of obesity, either BMI cut-off values should be revised to increase the sensitivity or the possibility of using other indirect methods of estimating the %FM should be explored.     

Serum Leptin and Skeletal Differences between Obese and Non-Obese Patients with Chronic Obstructive Pulmonary Disease

ObjectiveChronic obstructive pulmonary disease (COPD) affects body composition, adipokine secretion, and skeletal integrity. The aim was to determine the association between leptin, body mass (BM) and body composition parameters - fat mass (FM) and fat mass index (FMI), lean tissue mass (LTM), lean tissue mass index (LTMI) and bone mineral density (BMD) in 67 male COPD patients.MethodsBM, body composition and biochemical indicators were measured or calculated using standard methods. Data were analyzed according to groups: non-obese (N = 48, BMI 21.0-29.9 kg/m²) and obese (N = 19, BMI ≥ 30.0 kg/m²).ResultsIn the non-obese group statistically significant correlations were observed: negative ones of age with most BMD T scores, positive ones of BMI with all T scores, FM, FMI, LTMI and leptin, of FMI with leptin and all T scores, and of LTMI with most T scores. In the obese group also statistically significant correlations were found: positive ones of BMI with FMI, LTM, leptin and T scores (trochanter, total hip); of FMI with leptin; and of leptin with total hip T score.ConclusionA positive relationship between FMI and BMD was found only in non-obese but not in obese COPD patients. Leptin concentration was associated positively with the total hip T score only in obese COPD patients, suggesting its protective role on the skeleton of obese COPD patients.Key Words: Body mass, Body mass index, Fat mass, Fat mass index, Lean tissue mass, Lean tissue mass index, 25-OH vitamin D, Leptin, Bone mineral density     

Body Composition Characteristics of a Load-Capacity Model: Age-Dependent and Sex-Specific Percentiles in 5- to 17-Year-Old Children

IntroductionBody composition assessment is superior to the use of body mass index (BMI) to characterize the nutritional status in pediatric populations. For data interpretation, suitable reference data are needed; hence, we aimed to generate age-dependent and sex-specific body composition reference data in a larger population of children and adolescents in Germany.MethodsThis is a cross-sectional study on a representative group of 15,392 5- to 17-year-old children and adolescents. Body composition was assessed by bioelectrical impedance analysis using a population-specific algorithm validated against air displacement plethysmography. Age- and sex-specific percentiles for BMI, fat mass index (FMI), fat-free mass index (FFMI), and a “load-capacity model” (characterized by the ratios of fat mass [FM]/ fatt-free mass [FFM] and FM/FFM²) were modeled using the LMS method.ResultsBMI, FMI, FFMI, FM/FFM, and FM/FFM² curves showed similar shapes between boys and girls with steady increases in BMI, FMI, and FFMI, while FM/FFM²-centiles decreased during early childhood and adolescence. Sex differences were observed in FMI and FM/FFM percentiles with increases in FMI up to age 9 years followed by a steady decrease in FM/FFM during and after puberty with a fast-growing FFMI up to age 17 in boys. The prevalence of low FFM relative to FM reached more than 60% in overweight children and adolescents.ConclusionThese pediatric body composition reference data enable physicians and public health scientists to monitor body composition during growth and development and to interpret individual data. The data point out to an early risk of sarcopenia in overweight children and adolescents.     

Body composition characteristics and body fat distribution in lean women with polycystic ovary syndrome

Body composition, fat distribution and bone mineral density were examined in lean women suffering from polycystic ovary syndrome (PCOS) and compared with body composition and fat distribution characteristics of weight-matched lean controls. Ten women with PCOS and a body mass index (BMI) below 25.00 (kg/m(2)) and 10 healthy women with a BMI below 25.00 (kg/m(2)) matched for age and weight and BMI as controls were enrolled in this study. Body composition and bone density were measured by dual-energy- x-ray-absorptiometry and fat distribution patterns were calculated. Although matched for age, weight and BMI, lean PCOS patients showed a significantly higher amount of body fat and lower amount of lean body mass than the controls. The majority of PCOS patients showed an intermediate or android kind of fat distribution. Only 30% of the lean PCOS patients corresponded to the definition of gynoid fat distribution while this was true of all lean controls.     

Hierarchical differences in body composition of professional Sumo wrestlers

The body composition of 36 professional Sumo wrestlers and 39 collegiate male students were assessed densitometrically. The means of body weight, BMI and %fat for Sumo wrestlers were 117.1 kg, 36.5 and 26.2%, extraordinarily large compared with untrained men (p < 0.001). Results of the analysis of variance of divisions of Sumo wrestlers revealed significant differences in body weight, fat-free mass, fat mass, BMI, fat-free mass index (FFM/height2) and fat mass index (FM/height2). For the visual expression of the hierarchical differences of body composition, fat mass index and fat-free mass index of the wrestlers in various leagues were plotted on a body composition chart. Wrestlers in the Sekitori division had significantly larger fat-free mass index scores in comparison with wrestlers from the lower divisions who share a common area of the chart. The cut-off point of fat-free mass index which divided Sekitori wrestlers from other wrestlers is approximately 30 and this value may be one of the anthropometrical indications of whether or not a Sumo wrestler is destined to be successful.     

Comparison of body size and composition between young adult Japanese-Americans and Japanese nationals in the 1980s

Background : Data on body composition of American-born Japanese (Japanese-Americans) are scarce. Studies on differences of body composition between Japanese-Americans and Japanese nationals at various stages of life as well as at various times of measurements are useful for understanding the impact of lifestyle changes on body composition in the two societies. Aim : To see the differences in body size and composition between young adult Japanese-Americans and Japanese nationals. Subjects and Methods : Body size and composition of 50 Japanese-Americans consisting of 28 males and 22 females ranging in age from 18 to 23 years were compared with Japanese nationals matched for age and height. Body composition was measured using the underwater weighing method. The study was conducted in the 1980s in the USA and Japan. Results : The average percentage body fat of males was 13.7% for both Japanese-Americans and Japanese nationals, and that of females was approximately 24% for both groups, even though Japanese-American males and females had significantly greater body weight, fat-free mass, and body mass index than Japanese nationals. Conclusion : Although young adult Japanese-Americans showed larger body size than Japanese nationals, their percentage fat did not differ at this stage of life in the 1980s.     

Comparison of body size and composition between young adult Japanese-Americans and Japanese nationals in the 1980s

BACKGROUND: Data on body composition of American-born Japanese (Japanese-Americans) are scarce. Studies on differences of body composition between Japanese-Americans and Japanese nationals at various stages of life as well as at various times of measurements are useful for understanding the impact of lifestyle changes on body composition in the two societies. AIM: To see the differences in body size and composition between young adult Japanese-Americans and Japanese nationals. SUBJECTS AND METHODS: Body size and composition of 50 Japanese-Americans consisting of 28 males and 22 females ranging in age from 18 to 23 years were compared with Japanese nationals matched for age and height. Body composition was measured using the underwater weighing method. The study was conducted in the 1980s in the USA and Japan. RESULTS: The average percentage body fat of males was 13.7% for both Japanese-Americans and Japanese nationals, and that of females was approximately 24% for both groups, even though Japanese-American males and females had significantly greater body weight, fat-free mass, and body mass index than Japanese nationals. CONCLUSION: Although young adult Japanese-Americans showed larger body size than Japanese nationals, their percentage fat did not differ at this stage of life in the 1980s.     

Change in body mass index is a stronger predictor of change in fat mass than lean mass in elderly black and white women

The aim of this study was to determine the relation between change in body mass index (BMI) and changes in fat mass (FM), lean soft tissue (LST), and percentage body fat (%Fat) in elderly (67.6 ± 6.0 years) women varying in race (53 black, 144 white) who underwent measurements of BMI, FM, LST, and %Fat at baseline and after 2 years. The group did not markedly change body composition over 2 years (BMI = ?0.1 ± 1.5 kg/m², P = 0.53; FM = 0.0 ± 2.8 kg, P = 0.95; LST = ?0.4 ± 1.7 kg, P < 0.001; %Fat = 0.3 ± 2.0%, P = 0.06). Change in BMI predicted change in FM (r = 0.90, SEE = 1.19 kg FM, P < 0.001) but was less predictive of change in %Fat (r = 0.64, SEE = 1.54%Fat, P < 0.001). Change in BMI was curvilinearly related to change in LST adjusted for change in height (R = 0.76, SEE = 1.10 kg LST, P < 0.001). Change in BMI more strongly predicts change in FM than LST and could be used to monitor change in FM in community‐dwelling women. Am. J. Hum. Biol., 2009. © 2008 Wiley‐Liss, Inc.     

Assessment of body composition by using a new chart method

The body mass index (BMI, weight/height²), is commonly used as a simple and valid way of assessing body composition. However, the significance of the BMI is not clear, since body mass is composed of two main components: fat-free mass (FFM) and fat mass (FM), each with different densities. In order to graphically present body composition as a quantitative measure, a chart based on the fat-free mass index (FFMI, FFM/height²) and fat mass index (FMI; FM/height²), as reported in a previous paper (Hattori, J. Anthropol. Soc. Nippon 99:141–148, 1991), was revised by adding information on both the percentages of body fat (%fat) and the BMI. The benefit of the new chart method is its simplicity which comes from the application of two variables on a two dimensional chart. The chart containing the lines of %fat and the BMI can be of use in detecting multiple aspects of body composition since it provides four pieces of information at the same time: FMI, FFMI, BMI, and %fat. Am. J Hum. Biol. 9:573–578, 1997. © 1997 Wiley-Liss, Inc.     

Assessment of total body potassium in healthy Italian men

BACKGROUND: Whole-body (40)K counting is a valuable tool for assessing cellular changes in body composition with ageing. AIM: The objectives of this study were to assess total body potassium (TBK) and body cell mass (BCM) differences with age, and to compare TBK and BCM between individuals with a body mass index (BMI) < 25 kg m(-2) versus > 25 kg m(-2). SUBJECTS AND METHODS: Body composition of 840 healthy Italian men, 18-70 years of age, was measured by whole-body counting of (40)K. BCM (kg) was calculated as 0.00833 x TBK (mmol). RESULTS: Body weight did not differ among groups. TBK, TBK/height, TBK/body weight, and BCM were significantly lower for the 51-70-year-old group compared with all other groups. The 51-70-year-old group with a BMI < 25 kg m(-2) had significantly lower TBK, TBK/height, and BCM than all other decades with a BMI < 25 kg m(-2); whereas TBK/body weight was significantly lower than the 18-30 and 31-40-year-old groups. The 51-70-year-old group with a BMI > 25 kg m(-2) had significantly lower TBK, TBK/height, TBK/body weight, and BCM than all other decades with a BMI > 25 kg m(-2). CONCLUSION: TBK and BCM decrease significantly with ageing, which could result in decreased functional capacity in older adults.     

Validity of the body mass index as an indicator of adiposity in an ethnically diverse population of youths

The primary objective was to investigate the influences of ethnicity and pubertal stage on the ability of body mass index (BMI) to rank adiposity in a cohort of 402 Asian, African, Hispanic, and White Americans, aged 9–25 years. BMI was calculated from measured weight and height. Body composition and pubertal stage were determined by dual energy x-ray absorptiometry and self-rating, respectively. Multiple linear regression models with BMI, ethnicity, puberty, and age as explanatory variables were used to determine if ethnicity and pubertal stage modify the ability of BMI to predict percent of body weight that is fat (%BF). Spearman's correlation coefficients of BMI with %BF were also estimated. Both ethnicity and pubertal stage interacted with BMI. The correlation between BMI and %BF (r) was much higher in females (r = 0.72, P < 0.001) than in males (r = 0.15, NS). Among females, correlations did not vary much by pubertal stage, but tended to be higher in Blacks. Among males, correlations tended to be low during mid-puberty. However, a high correlation between BMI and lean body mass (LBM) was consistently observed in mid-pubertal males across all ethnic groups. Stratification by quartile of BMI showed that the correlation was >0 (P < .05) only in the highest quartile. Thus, in an ethnically diverse cohort of 9–25 year olds, the correlation between BMI and %BF is poor in the lower quartiles of BMI. In comparison, LBM correlates better with BMI than %BF in the lower quartiles of BMI. © 1996 Wiley-Liss, Inc.