Evaluation of Total Body Electrical Conductivity to Estimate Body Composition of a Small Mammal

ABSTRACT The ability to measure body composition is critical for studying the physiological ecology of animals. This is particularly true for small mammals that have a high metabolic rate. We evaluated a nondestructive method of body composition analysis that would allow accurate assessment of body fat, body water, and lean mass. We used total body electrical conductivity (TOBEC) to estimate body composition in the little brown myotis (Myotis lucifugus). In a sample of 46 individuals, TOBEC was both accurate and precise in estimating total body water and lean mass but was less effective at estimating total body fat. Mass-independent or whole-body compartments (i.e., total body water, total body fat, lean dry mass, and lean body mass) were more accurately estimated than mass-dependent or mass-specific body composition compartments (i.e., water content, fat index, and % lean dry mass). The TOBEC measurements we made using an SA-3000 analyzer were influenced by extremes in body temperature, as well as by aluminum and incoloy wing bands. Our study also presents a new method of restraint especially suited for small mammals and birds that increases precision of TOBEC measurements. This study shows that TOBEC is a potentially valuable tool for studying changes in body composition of small mammals and may provide insight into the physiological impacts of various life history stages such as postnatal growth, reproduction, and hibernation.     

Kinetics of stable isotope and body composition in olive baboons (Papio anubis) estimated by deuterium dilution space: a pilot study

Morphometrics and isotope-labelled water were used to determine body composition [total body water, total body fat and fat-free mass (FFM)] of three captive female olive baboons (Papio anubis). Mean mass was 16.5 kg, comparable with other captive settings but heavier than wild olive baboons. Average water content was 66%; FFM averaged 90.5%. Baboon females have less body fat than human counterparts. Compared with captive or wild baboons, these females were adequately nourished for their energy expenditure. A positive association between total mass and FFM existed, but due to the small sample no general relationship was observed for body fat or FFM and condition or size measures. The kinetics of deuterium equilibration in body fluids for baboons was determined as 3-4 hours after injection, similar to that for humans. Deuterium dilution technique appears to be an appropriate method for studying body composition in baboons, although a larger sample is needed for relationships between morphometric indices and body composition.     

湖南、湖北、贵州土家族成人的体成分比较

体成分指的是身体脂肪、蛋白质、肌肉、水等含量在体质量中所占的百分比.各成分之间的合理比例,对于维持机体的正常运行,十分重要.因此身体成分的研究一直是国内外研究的热点.体成分存在着人种和民族差异,因此它也是人类学研究的重要课题.目前的研究主要集中在中国青少年、大学生的体成分及体成分与其他身体指标的关系,而对于土家族的研究...     

Noninvasive estimation of body composition in small mammals: a comparison of conductive and morphometric techniques

Body fat stores may serve as an index of condition in mammals. Thus, techniques that measure fat content accurately are important for assessing the ecological correlates of condition in mammal populations. We compared the ability of two conductive techniques, bioelectrical impedance analysis (BIA) and total body electrical conductivity (TOBEC), to predict body composition with that of morphometric methods in three small mammal species: red squirrels (n=13), snowshoe hares (n=30), and yellow-bellied marmots (n=4). Animals were livetrapped in northern Idaho; BIA (all subjects) and TOBEC (squirrels only) measurements were taken following chemical immobilization in the field, and morphometric measurements were taken postmortem. Information provided by BIA and TOBEC failed to improve upon the predictive power of morphometric equations for total body water (TBW) and lean body mass (LBM) in squirrels and hares, which do not store substantial amounts of fat (<5% body mass comprised of fat). Although the same pattern held with respect to LBM in marmots, which accumulate substantial amounts of body fat (>10% body mass), a BIA-based model proved best at estimating TBW, suggesting that the usefulness of conductive techniques may be a function of fat deposition. However, regardless of the technique used to predict body composition, estimates of body fat furnished by our equations failed to approximate actual fat levels accurately in all three test species, probably because these techniques only provide indirect estimates of fat content. These results highlight the limitations inherent in contemporary methods of animal fat estimation and underscore the need for the development of direct and accurate measures of body fat in mammals.     

Evaluation of a Quantitative Magnetic Resonance Imaging System for Whole Body Composition Analysis in Rodents

We evaluated the EchoMRI‐900 combination rat and mouse quantitative magnetic resonance (QMR) body composition method in comparison to traditional whole‐body chemical carcass composition analysis (CCA) for measurements of fat and fat‐free mass in rodents. Live and postmortem (PM) QMR fat and lean mass measurements were obtained for lean, obese and outbred strains of rats and mice, and compared with measurements obtained using CCA. A second group of rats was measured before and after 18 h food or water deprivation. Significant positive correlations between QMR and CCA fat and lean mass measurements were shown for rats and mice. Although all live QMR fat and lean measurements were more precise than CCA for rats, values obtained for mice significantly differed from CCA for lean mass only. QMR performed PM slightly overestimated fat and lean values relative to live QMR but did not show lower precision than live QMR. Food deprivation reduced values for both fat and lean mass; water deprivation reduced estimates of lean mass only. In summary, all measurements using this QMR system were comparable to those obtained by CCA, but with higher overall precision, similar to previous reports for the murine QMR system. However, PM QMR measurements slightly overestimated live QMR values, and lean and fat mass measurements in this QMR system are influenced by hydration status and animal size, respectively. Despite these caveats, we conclude that the EchoMRI QMR system offers a fast in vivo method of body composition analysis, well correlated to but with greater overall precision than CCA.     

Effect of subclinical hypothyroidism on body fluid compartments.

OBJECTIVE: The present study was aimed to assess the effects of subclinical hypothyroidism on body composition (BC). SUBJECTS: Thirty-one women (age: 37 +/- 9.9 years) with a wide range of body mass index (BMI) were studied. Subclinical hypothyroidism was defined by a basal TSH > or = 4 mU/L and/or TRH stimulated peak > or = 30 mU/L. MEASUREMENTS: For each subject, weight, height, BMI, multifrequency bioelectrical impedance spectroscopy (BIS) and D2O and NaBr dilution tests were performed to assessed total body water (TBW) and extracellular water (ECW). Thyroid function (basal and TRH stimulated TSH, free T3, and free T4) were determined from fasting blood samples for all subjects. Total body dual energy X-ray absorptiometry (DXA) were used to measure fat mass (FM) and lean mass (Lean). RESULTS: The results of BIS were compared with the TBW and ECW estimated by the dilution techniques on the same individuals. The correlation was R2 = 0.65 for impedance at 5 kHz and ECW by NaBr and R2 = 0.72 for impedance at 100 kHz and TBW by D2O. Intracellular water (ICW) was calculated as differences between TBW and ECW measured by dilution methods. Percent of ECW and ICW were related to BMI (ANOVA, p < 0.001). No difference in TBW, body water distribution and body composition related to thyroid function was demonstrated. CONCLUSIONS: In our patients affected with subclinical hypothyroidism, with or without obesity, only obesity appeared related to TBW, ECW and ICW; the subclinical hypothyroidism, on the contrary, had no effect on compartments of body fluids. Bioimpedance is a valid tool to assess body fluid distribution in subclinical hypothyroidism.     

Changes in Body Composition in Anorexia Nervosa: Predictors of Recovery and Treatment Outcome

The restoration of body composition (BC) parameters is considered to be one of the most important goals in the treatment of patients with anorexia nervosa (AN). However, little is known about differences between AN diagnostic subtypes [restricting (AN-R) and binge/purging (AN-BP)] and weekly changes in BC during refeeding treatment. Therefore, the main objectives of our study were twofold: 1) to assess the changes in BC throughout nutritional treatment in an AN sample and 2) to analyze predictors of BC changes during treatment, as well as predictors of treatment outcome. The whole sample comprised 261 participants [118 adult females with AN (70 AN-R vs. 48 AN-BP), and 143 healthy controls]. BC was measured weekly during 15 weeks of day-hospital treatment using bioelectrical impedance analysis (BIA). Assessment measures also included the Eating Disorders Inventory-2, as well as a number of other clinical indices. Overall, the results showed that AN-R and AN-BP patients statistically differed in all BC measures at admission. However, no significant time×group interaction was found for almost all BC parameters. Significant time×group interactions were only found for basal metabolic rate (p = .041) and body mass index (BMI) (p = .035). Multiple regression models showed that the best predictors of pre-post changes in BC parameters (namely fat-free mass, muscular mass, total body water and BMI) were the baseline values of BC parameters. Stepwise predictive logistic regressions showed that only BMI and age were significantly associated with outcome, but not with the percentage of body fat. In conclusion, these data suggest that although AN patients tended to restore all BC parameters during nutritional treatment, only AN-BP patients obtained the same fat mass values as healthy controls. Put succinctly, the best predictors of changes in BC were baseline BC values, which did not, however, seem to influence treatment outcome.     

Estimation of human body composition by electrical impedance methods: a comparative study

This study 1) further validated the relationship between total body electrical conductivity (TOBEC) and densitometrically determined lean body mass (LBMd) and 2) compared with existing body composition techniques (densitometry, total body water, total body potassium, and anthropometry) two new electrical methods for the estimation of LBM: TOBEC, a uniform current induction method, and bioelectrical impedance analysis (BIA), a localized current injection method. In a sample of 75 male and female subjects ranging from 4.9 to 54.9% body fat the correlation between LBMd and LBM predicted from TOBEC by use of a previously developed regression equation was extremely strong (r = 0.962), thus confirming the validity of the TOBEC method. LBM predicted from BIA by use of prediction equations provided with the instrument also correlated with LBMd (r = 0.912) but overestimated LBM compared with LBMd in obese subjects. However, no such systematic error was apparent when new prediction equations derived from this heterogeneous sample of subjects were applied. Thus the TOBEC and BIA methods, which are based on the differing electrical properties of lean tissue and fat and which are convenient, rapid, and safe, correlate well with more cumbersome human body composition techniques.     

Comparison of DXA and CT in the Assessment of Body Composition in Premenopausal Women With Obesity and Anorexia Nervosa

Accurate methods for assessing body composition in subjects with obesity and anorexia nervosa (AN) are important for determination of metabolic and cardiovascular risk factors and to monitor therapeutic interventions. The purpose of our study was to assess the accuracy of dual‐energy X‐ray absorptiometry (DXA) for measuring abdominal and thigh fat, and thigh muscle mass in premenopausal women with obesity, AN, and normal weight compared to computed tomography (CT). In addition, we wanted to assess the impact of hydration on DXA‐derived measures of body composition by using bioelectrical impedance analysis (BIA). We studied a total of 91 premenopausal women (34 obese, 39 with AN, and 18 lean controls). Our results demonstrate strong correlations between DXA‐ and CT‐derived body composition measurements in AN, obese, and lean controls (r = 0.77–0.95, P < 0.0001). After controlling for total body water (TBW), the correlation coefficients were comparable. DXA trunk fat correlated with CT visceral fat (r = 0.51–0.70, P < 0.0001). DXA underestimated trunk and thigh fat and overestimated thigh muscle mass and this error increased with increasing weight. Our study showed that DXA is a useful method for assessing body composition in premenopausal women within the phenotypic spectrum ranging from obesity to AN. However, it is important to recognize that DXA may not accurately assess body composition in markedly obese women. The level of hydration does not significantly affect most DXA body composition measurements, with the exceptions of thigh fat.     

Measurement of subcutaneous adipose tissue using ultrasound images.

The objectives of this paper are to explore the potential of the ultrasound technique to quantify subcutaneous adipose tissue, and to explain the differences between skinfolds and ultrasound measurements across a large range of ages and levels of adiposity. The sample consisted of 115 men and 117 women aged 35 to 51 years, 132 girls and 145 boys aged 12 to 20 years. Subcutaneous fat thickness was measured at four sites using skinfolds calipers, and at seven sites using a real-time B-mode ultrasound scanner. Anthropometric measurements were obtained, and percent body fat was estimated using electric impedance. The agreement between skinfolds and ultrasound measurements was calculated for each age and sex group. The agreement between techniques, and the levels of correlation between body composition and fatness measurements were high in the sample of young men. However, the results were less consistent in the other groups. Site specific differences were also noted.     

Body Composition of African American and White Children: A 2‐Year Follow‐Up of the BAROC Study

Objective: To evaluate the 2‐year changes in body composition of white and African American boys and girls. Research Methods and Procedures: A total of 114 boys and girls ages 12 to 14 years with equal sex and ethnic distribution between African American and white races participated in measurements of body composition using DXA, underwater weighing (densitometry), skinfold thickness, corporal diameters, circumferences, isotope dilution (H₂¹⁸O), and bioelectric impedance. Results: Sixty‐eight of the 114 children advanced from Tanner Stages 1 and 2 to Tanner Stages 3 to 5 over a 2‐year period. More than 50% of the children were in the top 15th percentile according to normative data for body mass index but not for triceps skinfold. All measures except for percentage of fat, density, and four of the six skinfolds increased significantly during the 2 years, with no differences between races, genders, or fat group. The boys who advanced in Tanner Stage reduced their percentage of fat and a number of skinfolds and increased their lean body mass, but the girls did not. The percentage of water was significantly higher in the fatter children and declined significantly over 2 years. Most children remained in the same quartile of body fat, lean body mass, and bone mineral content over 2 years. Discussion: The data are consistent with the hypothesis that over 2 years, growth is the major determinant of changing body composition, with body‐fat group and sexual maturation being additional variables.     

Validity of Six Field and Laboratory Methods for Measurement of Body Composition in Boys

Objective: To determine the validity of the following six body composition methods against a reference method (three‐component model): air displacement plethysmography (BODPOD); estimation from body density using BODPOD; skinfold thickness using the Slaughter equations; bioelectrical impedance, both leg‐leg (TANITA) and hand—foot (Bodystat) approaches; and total body water. Research Methods and Procedures: Forty‐two healthy white 10‐ to 14‐year‐old boys (mean age, 12.9 ± 1.0 years) were enrolled in this study. Measures of body fat percentage and body fat mass derived from the three‐component model were used as the reference method. Validity of all of the other methods was assessed by comparison against the reference by calculation of biases and limits of agreement. Results: Mean body fatness measured using the reference method was 16.4 ± 11.6% and 8.7 ± 7.0 kg. Estimates of fatness from total body water had the narrowest limits of agreement relative to the reference (+0.9 ± 5.0% body fat; +0.5 ± 2.9 kg fat mass). For all other methods tested, we observed large biases and very wide limits of agreement. Discussion: This study suggests that the validity of newer field and laboratory methods for estimation of body composition is poor in adolescent boys. For applications where high accuracy of estimation at the individual level is essential, only reference methods would be acceptable.     

Body composition assessment in type 1 diabetes mellitus patients over 15 years old.

BACKGROUND: The aim of the present study was to assess the anthropometric characteristics and body composition in type 1 diabetic patients and compare the results with a randomly selected control population. MATERIAL AND METHODS: We studied 75 type 1 diabetic patients, 43 male and 32 female, recruited from consecutive diagnosed type 1 diabetic patients attending the Endocrine Unit and treated with a intensive insulin regimen, and 93 control subjects, 44 males and 49 females representative of the census of this city. We performed a dietary recall in patients and determined anthropometric characteristics, both in patients and controls, body weight, height, body-mass index, waist-hip ratio and body composition parameters: total body water, free-fat mass, body free-fat mass, fat mass and body fat by bioelectrical impedance analyser. RESULTS: In diabetic male patients, we observed lower waist-hip ratio than in controls, 0.84 +/- 0.06 vs. 0.88 +/- 0.07, p = 0.021, higher free-fat mass in female diabetic patients, 48.5 +/- 5.6 vs. 45.6 +/- 5.9 kg, p = 0.03, lower fat mass in male diabetic patients, 9.5 +/- 6.9 vs. 14.6 +/- 8.5 kg, p = 0.003. We did not find any correlation among the parameters of body composition and dietary macronutrient intake in patients. CONCLUSIONS: The present study exposes the differences in anthropometric characteristics and body composition in type 1 diabetes mellitus, especially lower waist-hip ratio in male, higher free-fat mass in female and lower fat mass in male.     

Changes in Total Body Water and Body Fat in Young Women in the Course of Menstrual Cycle

This paper reports on the changes in total body water and body fat in young women in during the course of the menstrual cycle. We followed 40 young women with an average age of 21.52 years, and took bioelectrical impedance measurements during two menstrual cycles. The measurements were taken in three phases of the menstrual cycle. We found that body mass and total body water fluctuate during the menstrual cycle. Both parameters are highest in the luteal phase and lowest in the late folicular phase; 65% of the young women demonstrated these changes. The presence or absence of premenstrual symptoms had no influence on these values.     

Body build related body composition and nutrition in adulthood--a comparison of skinfold thickness measurement and bioelectric impedance analysis

The objective of the present study was to conduct a comprehensive analysis of body build, body composition and nutritional status. The study sample consists of 498 men and women aged from 35 to 65 years. Subjects underwent a detailed anthropometric examination incompassing thirty-one body measurements, eleven skinfold thickness measurements, and bioelectrical impedance analysis for determination of body composition. Dietary intake was assessed by a semiquantitative food frequency questionnaire. Body composition was clearly associated with age and body build. Somatometric differentiation by use of the metric index showed that percentage of body fat was significantly higher in pycnomorphic compared to leptomorphic subjects, whereas reported dietary energy intake was lower. Comparison of estimates of body fat showed considerably deviating results for skinfold thickness measurements and bioelectrical impedance analysis depending on the equations used. This was especially pronounced in obese subjects, where, on an average, bioelectrical impedance analysis resulted in higher values for percentage of body fat compared to skinfold thickness measurements. We conclude that for assessment of nutritional status body composition should be investigated taking into account body build in addition to age and sex.     

New insights into body composition assessment in obese women.

During treatment of patients with non-insulin-dependent diabetes mellitus, there may be marked body weight loss. Therefore, body composition should be monitored to check for a decrease in fat mass alone, without an excessive decrease of both fat-free mass and total body water. Accordingly, it is useful to monitor the hydration of these patients. One method that allows us to check the status of body hydration is the multifrequency bioelectric impedance analysis (MFBIA). It makes use of formulas that estimate total body water on the basis of the concept that the human body may be approximated to a cylinder of length equal to body height. In normal subjects body water estimates are sufficiently accurate, but in obese subjects the true hydration status may be overestimated. In this report, we describe the accuracy of mathematical models previously described in the literature, and correct for the overestimation of total body water in obese subjects by means of a new equation based on a new model. The coefficients for each model have been recalculated by the weighing of our sample in order to test the accuracy of estimates obtained with the equations. This new model includes both body volume and two impedances at appropriate frequencies useful for identifying two terms strictly related to extra- and intra-cellular water. The new formulas do not include body weight, but they include the body volume, a parameter more closely related to the biophysical reference model. Fifty-five overweight females, body mass index ranging from 26.8 to 50.2 kg/m2, were enrolled in the study. The proposed equations, taking advantage of two impedance values at appropriate frequencies, better predict total body water in obese women. This was particularly evident when the results obtained with the multifrequency bioelectric impedance analysis and deuterium isotopic oxide dilution method were compared. Although this last method is considered the "gold standard," it is not suitable for use in routine clinical practice. In conclusion, evaluation of total body composition by means of bioelectric impedance analysis might be included in programs for the prevention of non-insulin-dependent diabetes and for monitoring weight loss during overt pathology.     

Reliability of Multifrequency Bioelectrical Impedance Analysis to Quantify Body Composition in Patients After Musculoskeletal Trauma

BackgroundChanges in body composition, especially loss of lean mass, commonly occur in the orthopedic trauma population due to physical inactivity and inadequate nutrition. The purpose of this study was to assess inter-rater and intra-rater reliability of a portable bioelectrical impedance analysis (BIA) device to measure body composition in an orthopedic trauma population after operative fracture fixation. BIA uses a weak electric current to measure impedance (resistance) in the body and uses this to calculate the components of body composition using extensively studied formulas.MethodsTwenty subjects were enrolled, up to 72 hours after operative fixation of musculoskeletal injuries and underwent body composition measurements by two independent raters. One measurement was obtained by each rater at the time of enrollment and again between 1-4 hours after the initial measurement. Reliability was assessed using intraclass correlation coefficients (ICC) and minimum detectable change (MDC) values were calculated from these results.ResultsInter-rater reliability was excellent with ICC values for body fat mass (BFM), lean body mass (LBM), skeletal muscle mass (SMM), dry lean mass (DLM), and percent body fat (PBF) of 0.993, 0.984, 0.984, 0.979, and 0.986 respectively. Intra-rater reliability was also high for BFM, LBM, SMM, DLM, and PBF, at 0.994, 0.989, 0.990, 0.983, 0.987 (rater 1) and 0.994, 0.988, 0.989, 0.985, 0.989 (rater 2). MDC values were calculated to be 4.05 kg for BFM, 4.10 kg for LBM, 2.45 kg for SMM, 1.21 kg for DLM, and 4.83% for PBF.ConclusionPortable BIA devices are a versatile and attractive option that can reliably be used to assess body composition and changes in lean body mass in the orthopedic trauma population for both research and clinical endeavors. Level of Evidence: III     

Effect of physical training on body composition in Moscow adolescents

The influence of physical activity on body mass components has been studied using a sample of Moscow children. 195 girls and 259 boys of Russian ethnicity from 12 to 17 years old were investigated cross-sectionally in 2005 in different Moscow schools. According to the level of physical activity they were divided into three groups: 1-those who did not take part in regular physical exercise (44 boys and 50 girls); 2-those who took part in special sports programs in general education schools (82 boys and 82 girls); 3-students of special sports schools with a high sports ranking (133 boys and 63 girls). The program included anthropometric measurements, evaluation of sexual maturation indices, somatotypes, and "functional" traits (diastolic and systolic blood pressure, pulse rate, hand grip, etc). For the study of body composition, bioelectrical impedance analysis (BIA) was used. The estimates of body mass components were also calculated using the anthropometric measurements. For the fat component, the estimates obtained by BIA and the anthropometric methods were highly correlated: r=0.85-0.88. Age changes of BIA measurements and body components were analysed. With multiple regression analysis it was shown that BIA measurements are dependent on a great number of morphological and functional traits, with the most informative sets of traits being selected. The degree of physical activity has a strong effect on body components: the contents of fat-free mass (FFM) and total body water (TBW) significantly increase, and the fat mass (FM) in girls decreases.     

生物电阻抗法测定广西京族的体成分

本文利用生物电阻抗法对广西京族的体成分进行了测定,初步分析了其体成分形成的原因。研究组于2020年12月在广西壮族自治区东兴市“京族三岛”测定了430例京族成人（男182例,女248例）的16项指标。结果表明,京族男、女性的体质量、总肌肉量、躯干肌肉量、推定骨量、总能量代谢与年龄呈显著负相关。体成分随年龄增长而发生的变化,主要是自然的生理变化和劳动强度下降所致。随着年龄增长,男性的体脂率升高,这主要是躯干脂肪增多造成的。京族男性的体质量、总肌肉量、推定骨量、总能量代谢、水分率、四肢和躯干肌肉量均大于女性,而体脂率、四肢和躯干脂肪率均小于女性。京族男性比女性拥有更大的体质量和更高比例的骨骼肌,这两方面因素再加上劳动强度的差异,可能导致男性肌肉量、骨量、脂肪率等体成分与女性存在差异。总体来看,京族成人身体偏胖,脂肪含量较高,身体含水量基本正常,体成分特征与同为南亚语系或同在沿海地区的其他中国族群并不相似,而相对更接近于中国蒙古族,并且表现在体质量、体脂率、水分率等方面接近。生活环境、社会经济、日常饮食和劳动强度等因素是导致京族成人体质量及体脂率较高的原因。     

Are Ethnic and Gender Specific Equations Needed to Derive Fat Free Mass from Bioelectrical Impedance in Children of South Asian,Black African-Caribbean and White European Origin? Results of the Assessment of Body Composition in Children Study

Background

Bioelectrical impedance analysis (BIA) is a potentially valuable method for assessing lean mass and body fat levels in children from different ethnic groups. We examined the need for ethnic- and gender-specific equations for estimating fat free mass (FFM) from BIA in children from different ethnic groups and examined their effects on the assessment of ethnic differences in body fat.

Methods

Cross-sectional study of children aged 8–10 years in London Primary schools including 325 South Asians, 250 black African-Caribbeans and 289 white Europeans with measurements of height, weight and arm-leg impedance (Z; Bodystat 1500). Total body water was estimated from deuterium dilution and converted to FFM. Multilevel models were used to derive three types of equation {A: FFM = linear combination(height+weight+Z); B: FFM = linear combination(height²/Z); C: FFM = linear combination(height²/Z+weight)}.

Results

Ethnicity and gender were important predictors of FFM and improved model fit in all equations. The models of best fit were ethnicity and gender specific versions of equation A, followed by equation C; these provided accurate assessments of ethnic differences in FFM and FM. In contrast, the use of generic equations led to underestimation of both the negative South Asian-white European FFM difference and the positive black African-Caribbean-white European FFM difference (by 0.53 kg and by 0.73 kg respectively for equation A). The use of generic equations underestimated the positive South Asian-white European difference in fat mass (FM) and overestimated the positive black African-Caribbean-white European difference in FM (by 4.7% and 10.1% respectively for equation A). Consistent results were observed when the equations were applied to a large external data set.

Conclusions

Ethnic- and gender-specific equations for predicting FFM from BIA provide better estimates of ethnic differences in FFM and FM in children, while generic equations can misrepresent these ethnic differences.