OBJECTIVEAge-specific body mass index (BMI) is commonly employed as an index of adiposity for pediatric clinical and research purposes. However, BMI fails to discriminate between fat and lean mass, making it an imperfect monitor for obesity. We hypothesized that simple anthropometry and organized non-aquatic physical activity assessment (PA) would provide superior explanatory value for pediatric body composition outcomes.RESEARCH METHODS AND PROCEDURESIn a cross-sectional analysis, whole body DXA assessed body composition in 120 pre-menarcheal girls. Questionnaires were used to record and generate annual means for PA. Age, Tanner breast self-stage, height, weight, BMI, skinfold thicknesses, girths and PA were examined as potential predictors of body composition outcomes, using backward stepwise multiple linear regression. A parsimonious regression model was developed in 75% and cross-validated in 25% of the total sample; models were rerun with the total sample.RESULTSSubject means were as follows: age = 10.4±1.2 y; lean soft tissue (LST) = 24.4±4.2 kg; fat mass (FM) = 8.1±4.1 kg; BMI = 17.6±2.5 kg/m2; PA = 6.8±5.0 h/wk; Tanner breast self-stage ranged from 1 to 3. BMI for age Z scores ranged from -2 to 2.1. Age and BMI alone yielded adjusted model r2=0.44 to 0.78. The final model, including age, height, weight, biceps skinfold and PA, yielded adjusted r2=0.61 to 0.92, P <0.001. Prediction of LST and FM increased from r2=0.64 and 0.76 to r2=0.92 and 0.91, respectively.DISCUSSIONCompared to BMI and age alone, models including biceps skinfold, PA, height, weight and age had superior explanatory value for clinically-relevant body composition outcomes, and are feasible for clinical use.
OBJECTIVE:Anthropometrics are commonly used indices of total and central adiposity. No study has compared anthropometric measurements to dual-energy X-ray absorptiometry (DXA) measurements as correlates of cardiovascular risks in a nationally representative sample of youth. We aimed to evaluate the validity of anthropometrics compared to DXA-assessed adiposity in relation to cardiovascular risks in youth aged 8-19 years. METHODS:Data were from the National Health and Nutrition Examination Survey 1999-2004 (n=7013). We examined the correlations between anthropometric and DXA measures of adiposity (i.e., body mass index (BMI) versus percent fat mass (%FM) and fat mass index, and waist circumference (WC) and waist-to-height ratio (WHtR) versus percent trunk fat mass (%TFM)) with nine cardiovascular risks, stratified by sex and age, or race-ethnicity. RESULTS:Anthropometric and DXA adiposity measures were significantly correlated with insulin (r: 0.48 to 0.66), C-reactive protein (r: 0.47 to 0.58), triglycerides (r: 0.15 to 0.41), high-density lipoprotein cholesterol (HDL-C, r: -0.44 to -0.22), systolic blood pressure (SBP, r: 0.10 to 0.31), low-density lipoprotein cholesterol (r: 0.09 to 0.30), total cholesterol (TC, r: 0.01 to 0.29) and glucose (r: 0.05 to 0.20). Only in all youth, BMI was more strongly correlated with SBP (0.22 vs. 0.12, P<0.0001) and HDL-C (-0.34 vs. -0.25, P<0.0001) than %FM; WC but not WHtR was more strongly correlated with HDL-C (-0.37 vs. -0.30, P<0.0001) but less strongly associated with TC (0.12 vs. 0.21, P<0.0001) than %TFM. CONCLUSIONS:DXA adiposity measures do not produce stronger associations with cardiovascular risk factors in youth than BMI or WC.
OBJECTIVE:Assess the utility of peripheral quantitative computed tomography (pQCT) for estimating whole body fat in adolescent girls.RESEARCH METHODS AND PROCEDURES:Our sample included 458 girls (aged 10.7 ± 1.1y, mean BMI = 18.5 ± 3.3 kg/m2) who had DXA scans for whole body percent fat (DXA %Fat). Soft tissue analysis of pQCT scans provided thigh and calf subcutaneous percent fat and thigh and calf muscle density (muscle fat content surrogates). Anthropometric variables included weight, height and BMI. Indices of maturity included age and maturity offset. The total sample was split into validation (VS; n = 304) and cross-validation (CS; n = 154) samples. Linear regression was used to develop prediction equations for estimating DXA %Fat from anthropometric variables and pQCT-derived soft tissue components in VS and the best prediction equation was applied to CS.RESULTS:Thigh and calf SFA %Fat were positively correlated with DXA %Fat (r = 0.84 to 0.85; p <0.001) and thigh and calf muscle densities were inversely related to DXA %Fat (r = -0.30 to -0.44; p < 0.001). The best equation for estimating %Fat included thigh and calf SFA %Fat and thigh and calf muscle density (adj. R2 = 0.90; SEE = 2.7%). Bland-Altman analysis in CS showed accurate estimates of percent fat (adj. R2 = 0.89; SEE = 2.7%) with no bias.DISCUSSION:Peripheral QCT derived indices of adiposity can be used to accurately estimate whole body percent fat in adolescent girls.
To investigate the effects of the atypical antipsychotics drugs (AADs), olanzapine and risperidone, on femoral bone characteristics in female C57BL/6J mice.Mice were treated with placebo or AADs (olanzapine or risperidone) for 3-4 weeks. Femoral cortical and trabecular bone characteristics were determined using micro-computed tomography.Olanzapine-treated mice tended to have lower trabecular bone volume (P = 0.088) and connectivity (P = 0.057) but no significant differences in bone density (P = 0.521) relative to controls. Risperidone-treated mice had significantly lower trabecular bone density (P = 0.001) and volume (P = 0.008), bone volume/total volume (P = 0.001), connectivity (P = 0.007), and trabecular number (P = 0.003) relative to controls. Cortical bone was not significantly affected by olanzapine or risperidone treatment.AADs inhibited trabecular bone accrual in C57BL/6J mice suggesting that alternative treatment options may need to be considered for the schizophrenia patient with potential osteoporosis risk.
PURPOSE:Adipocyte cell size varies among individuals and importantly, is inversely correlated with insulin sensitivity, and modifiable by weight loss or pharmaceutical agents. However, there are no non-invasive, in vivo methods for adipocyte cell size determination. Here we apply Chemical-Shift Water-Fat MRI to in vivo measures of subcutaneous (inguinal) and visceral (gonadal) white adipose tissue (WAT) to determine whether the fat-signal fraction (FF) is a sensitive indicator of adipocyte cell size.MATERIALS AND METHODS:C57BL/6J male mice (8 weeks old) were singly housed and fed a low-fat diet, high-fat diet or very high-fat diet (n = 16 or 15/group) for 8 weeks. Food intake, body weight and composition were measured; CS-MRI was performed on a 9.4 Tesla Bruker magnet with respiratory gating and anesthesia. Histology was acquired for gonadal WAT; both gonadal and inguinal WAT were fixed with osmium tetroxide and then measured through Image J for cell size.RESULTS:Mice fed with higher fat content diets gained significantly more body weight, fat and lean mass while maintaining higher energy intakes over the 8 weeks. There was no significant difference in fat fraction for either gonadal (P = 0.1295) or inguinal (P = 0.4704) WAT among the three groups, despite significantly larger adipocytes (P <0.0001) in mice on high fat diets.CONCLUSION:Although diet-induced obesity significantly increased the amount of fat mass, as well as mean and overall white adipocyte cell size, the CS-MRI measured fat fraction between groups were not significantly different. These results do not support the utility of CS-MRI measured FF for in vivo determination of adipocyte cell size.
OBJECTIVE:Accumulation of intra-abdominal (visceral) adipose tissue, independent of total adiposity, is associated with development of metabolic abnormalities such as insulin resistance and type-2 diabetes in children and adults. The objective of this study was to develop prediction equations for estimating visceral adiposity (VAT) measured by magnetic resonance imaging (MRI) using anthropometric variables and measures of abdominal fat mass from DXA in adolescents and young adults.METHODS:Cross-sectional data was collected from a multiethnic population of seventy males and females, aged 12-25 years, with BMI ranging from 14.5-38.1 kg/m2. Android (AFM; android region as defined by manufacturers instruction) and lumbar L1-L4 regional fat masses were assessed using DXA (GE Lunar Prodigy; GE Lunar Corp, Madison, WI, USA). Criterion measures of intra-abdominal visceral fat were obtained using single-slice MRI (General Electric Signa Model 5x 1.5T) and VAT area was analyzed at the level OF L4-L5. Image analysis was carried out using ZedView 3.1.RESULTS:DXA measures of AFM (r=0.76) and L1-L4 (r=0.71) were significantly (P<0.0001) correlated with MRI-measured VAT. DXA AFM, together with gender and weight, explained 62% of the variance in VAT (SEE=10.06 cm2). DXA L1-L4 fat mass with gender explained 54% of the variance in VAT (SEE=11.08 cm2). Addition of the significant interaction, gender × DXA fat mass, improved prediction of VAT from AFM (Radj2=0.61, SEE=10.10cm2) and L1-L4 (Radj2=0.59, SEE=10.39cm2).CONCLUSION:These results demonstrate that VAT is accurately estimated from regional fat masses measured by DXA in adolescents and young adults.
OBJECTIVE: Body Adiposity Index (BAI), a new surrogate measure of body fat (hip circumference/[height 1.5-18]), has been proposed as a more accurate alternative to BMI. We compared BAI with BMI and their correlations with measures of body fat, waist circumference (WC), and indirect indices of fat pre- and post-Roux-en-Y gastric bypass (RYGB). METHODS: Sixteen clinically severe obese (CSO) non-diabetic women (age = 33.9± 7.9 SD; BMI = 46.5±9.5 kg/m(2)) were assessed pre-surgery, and at 2 (n=9) and 5 mo (n=8) post-surgery. Body fat percentage (% fat) was estimated with bioimpedance analysis (BIA), air displacement plethysmography (ADP), and dual-energy x-ray absorptiometry (DXA). WC, an indicator of central fat, and both plasma leptin (ng/ml) and insulin (mU/l) concentrations were measured as indirect body fat indices. Pre- and post-surgery values were analyzed with Pearson correlations and linear regressions. RESULTS: BAI and BMI correlated significantly with each other pre-surgery and at each time point post surgery. BAI and BMI also correlated significantly with % fat from BIA and ADP; however, only BMI correlated significantly with % fat from DXA pre- and post-RYGB. BMI was the single best predictor of WC and leptin at 2 and 5 mo post-surgery and had significant longitudinal changes correlating with % fat from BIA and DXA as well as with leptin. DISCUSSION: Both BAI and BMI were good surrogates of % fat as estimated from BIA and ADP, but only BMI was a good surrogate of % fat from DXA in CSO women. Thus, BAI may not be a better alternative to BMI.
BACKGROUND Bioelectrical impedance analysis (BIA) is a simple tool to assess total body water (TBW), from which body composition can be estimated using statistical equations. However, standard BIA equations have not been sufficiently validated during pregnancy, in HIV infection, or in sub-Saharan Africa. We therefore compared TBW estimates from multifrequency BIA with those from the reference method deuterium isotope dilution (Deut) in a cohort of 30 HIV-uninfected and 30 HIV-infected pregnant women from Tanzania. METHODS We enrolled pregnant women presenting for routine antenatal care and collected data on pregnancy outcomes. At each trimester of gestation and once at 10-wk post-partum, we measured maternal anthropometry, TBWBIA, and TBWDeut. RESULTS TBWBIA was highly correlated at each time point with TBWDeut among HIV-infected (all P ≤0.001) and HIV-uninfected women (all P <0.0001). During pregnancy, mean TBWBIA progressively underestimated TBWDeut in the overall cohort; trimester-specific differences (mean ±SD) were -1.02 ±2.36 kg, -1.47 ±2.43 kg, and -2.42 ±2.63 kg, respectively. The difference at 10-wk postpartum was small (-0.24 ±2.07 kg). In Bland-Altman and regression models, TBWBIA was subject to a systematic predictive bias at each antenatal and postnatal time point (all P ≤0.038). Among HIV-positive women, TBWDeut measured during the first (P =0.02) and second trimester (P =0.03) was positively related to birthweight. CONCLUSIONS The validity of current BIA equations to assess TBW during pregnancy and in the postpartum period among women from sub-Saharan Africa remains uncertain. Deuterium dilution may assess aspects of maternal body composition relevant for pregnancy outcomes among HIV-infected women.
Mass-specific basal metabolic rate (mass-specific BMR), defined as the resting energy expenditure per unit body mass per day, is an important parameter in energy metabolism research. However, a mechanistic explanation for magnitude of mass-specific BMR remains lacking. The objective of the present study was to validate the applicability of a proposed mass-specific BMR model in healthy adults. A mechanistic model was developed at the organ-tissue level, mass-specific BMR = Σ(Ki × Fi), where Fi is the fraction of body mass as individual organs and tissues, and Ki is the specific resting metabolic rate of major organs and tissues. The Fi values were measured by multiple MRI scans and the Ki values were suggested by Elia in 1992. A database of healthy non-elderly non-obese adults (age 20 - 49 yrs, BMI <30 kg/m2) included 49 men and 57 women. Measured and predicted mass-specific BMR of all subjects was 21.6 ± 1.9 (mean ± SD) and 21.7 ± 1.6 kcal/kg per day, respectively. The measured mass-specific BMR was correlated with the predicted mass-specific BMR (r = 0.82, P <0.001). A Bland-Altman plot showed no significant trend (r = 0.022, P = 0.50) between the measured and predicted mass-specific BMR, versus the average of measured and predicted mass-specific BMR. In conclusion, the proposed mechanistic model was validated in non-elderly non-obese adults and can help to understand the inherent relationship between mass-specific BMR and body composition.
OBJECTIVE: To develop a magnetic resonance imaging (MRI)-based approach for quantifying absolute fat mass in organs, muscles, and adipose tissues, and to validate its accuracy against reference chemical analysis (CA). METHODS: Chemical-shift imaging can accurately decompose water and fat signals from the acquired MRI data. A proton density fat fraction (PDFF) can be computed from the separated images, and reflects the relative fat content on a voxel-by-voxel basis. The PDFF is mathematically closely related to the fat mass fraction and can be converted to absolute fat mass in grams by multiplying by the voxel volume and the mass density of fat. In this validation study, 97 freshly excised and unique samples from four pigs, comprising of organs, muscles, and adipose and lean tissues were imaged by MRI and then analyzed independently by CA. Linear regression was used to assess correlation, agreement, and measurement differences between MRI and CA. RESULTS: Considering all 97 samples, a strong correlation and agreement was obtained between MRI and CA-derived fat mass (slope = 1.01, intercept = 1.99g, r(2) = 0.98, p < 0.01). The mean difference d between MRI and CA was 2.17±3.40g. MRI did not exhibit any tendency to under or overestimate CA (p > 0.05). When considering samples from each pig separately, the results were (slope = 1.05, intercept = 1.11g, r(2) = 0.98, d = 2.66±4.36g), (slope = 0.99, intercept = 2.33g, r(2) = 0.99, d = 1.88±2.68g), (slope = 1.07, intercept = 1.52g, r(2) = 0.96, d = 2.73±2.50g), and (slope=0.92, intercept=2.84g, r(2) = 0.97, d = 1.18±3.90g), respectively. CONCLUSION: Chemical-shift MRI and PDFF provides an accurate means of determining absolute fat mass in organs, muscles, and adipose and lean tissues.
The purpose of this study was to compare Tanita tetrapolar foot‐to‐foot bioelectrical impedance analysis (Model TBF‐310, Tanita Corporation of America, Arlington Heights, IL; Tanita‐BIA) and fan beam dual‐energy X‐ray absorptiometry (Hologic Discovery A v12.6, Waltham, MA; DXA). Seventy Hispanic diabetic participants (23 male, 47 female; mean age: 53.03 ± 10.32 yrs; mean weight: 81.45 ± 17.65 kg; and mean body mass index: 31.40 ± 6.80 kg/m^2) participated in a three‐month diabetes education follow‐up study. Fat mass (FM), percent fat mass (%FM), and fat free mass (FFM) were compared using both relative and absolute measures of agreement. Relative measures included Pearson's and Spearman's rank correlation coefficients while absolute agreement was assessed using Bland‐Altman analyses and concordance correlation with 95% confidence intervals calculated using a bootstrap resampling of the data. Pearson's (FM: 0.96, %FM: 0.91, and FFM: 0.82), and Spearman's rank (FM: 0.94, %FM: 0.91, and FFM: 0.92) correlation coefficients showed high measures of association. Bland‐Altman and concordance analyses also demonstrated good agreement [FM: 0.93 (95% CI: 0.89, 0.96)], [%FM: 0.86 (95% CI: 0.79, 0.90)], and [FFM: 0.93 (95% CI: 0.89, 0.96)]. Tanita‐BIA may provide valid measures of FM, %FM and FFM in Hispanic diabetics, and could be a convenient and practical approach for assessment in community‐based research. This study was supported in part by grants 03‐00335 from the Centers for Medicare and Medicaid Services and 5P20MD001632 from the National Institutes of Health.
Fat distribution, especially increased visceral fat, may be as important as overall obesity in increasing risk of heart disease, type 2 diabetes and certain cancers. Risk of disease, as well as visceral fat, increases dramatically with age. Cross-sectional data suggests that increased risk of disease may be largely prevented if the age related increase in visceral fat does not occur. The objective of this short review is to present data that shows visceral fat increasing over 200% in men and 400% in women between the 3rd and 7th decades, show that a combination of weight gain, loss of muscle, and a shift from peripheral to central fat patterning contributes to this increase, and identify hormones that may be responsible for the shift. Finally, the review will show how participation in exercise can slow the age related shift in visceral fat.
Osteoporosis is characterized by low bone mass and micro-architectural deterioration resulting in a reduction in bone strength and an increased susceptibility to fracture [1]. In the U.S., its prevalence is projected to increase from 10–12 million individuals over age 50 to nearly 14 million individuals by 2020 [2]. In addition, an estimated 47 million individuals with osteopenia (low bone mass) are at risk for future osteoporosis [2]. Current estimates suggest 30–50% of women and 15–30% of men will suffer a fracture due to osteoporosis sometime in their lifetime [1]. Approximately 1.5 million fractures occur in the U.S. each year. Fractures occur most frequently at the hip, spine, and distal forearm. Hip fractures are the most serious because they require hospitalization, and are associated with significant pain, disability, and excess mortality. A reported 315,000 Americans age 45 and older were admitted to hospitals with hip fractures in 2001 [2]. Sadly, after sustaining a hip fracture, 20% of people die within the first year [3], 40% are unable to work independently, and 60% require long-term care [4]. Vertebral fractures are also associated with significant disability and morbidity, including decreased function, back pain, loss of height and deformity, and a reduced quality of life. Moreover, there are data showing that following a vertebral fracture there is a 2–3 times increased risk of a subsequent fracture of a different type, and at least a fourfold increase in risk of another vertebral fracture [5]. The economic costs of osteoporotic fractures are enormous. In the U.S. alone, the estimated cost per year for osteoporotic-related fractures is about $17 billion [2], and the costs are projected to increase to approximately $45 billion over the next 10 years. Development of effective osteoporosis prevention strategies is clearly a public health imperative.
OBJECTIVE: The objective of this study was to determine associations of anthropometric measures of thigh and abdominal adipose tissue with metabolic risk factors, and whether these associations differed with ethnicity. We hypothesized that thigh circumference (ThC) would have an independent favorable association with insulin sensitivity, lipids, and blood pressure, whereas waist circumference (WC) would have an independent deleterious association with these variables in both African Americans (AA) and European Americans (EA). METHODS: Subjects were 228 healthy, overweight, premenopausal AA and EA women. Insulin sensitivity was assessed by intravenous glucose tolerance test and minimal modeling. Simple relationships between anthropometric measures and risk factors were determined by Pearson correlation analysis. Partial correlation coefficients were determined for circumference measures adjusted for thigh and abdominal skinfolds to differentiate relationships between thigh and abdominal subcutaneous fat from thigh muscle and deeper abdominal fat, respectively. RESULTS: In EA but not AA, ThC was positively associated with insulin sensitivity, independent of thigh skinfold. In both EA and AA, ThC was associated with a desirable lipid profile. In AA but not EA, WC was associated with lower insulin sensitivity and a less desirable metabolic profile. CONCLUSION: Results suggest that thigh muscle (ThC adjusted for thigh skinfold) may be metabolically protective in EA but not AA. In contrast, WC was a better indicator of insulin sensitivity and metabolic health in AA. Further investigation is needed to verify the association between thigh muscle and metabolic health, and to probe the reason for the observed ethnic specificity of the associations between anthropometric measures and metabolic risk factors.
OBJECTIVE: We have previously shown that surrounding fat causes an increase of up to 21% in bone mineral density (BMD) measured by Lunar 'Intelligent DXA' (iDXA), one of the latest generation dual energy X-ray absorptiometry (DXA) scanners [1]. The purpose of our study was to see if it was possible to avoid this artifact when measuring the BMD of metacarpals II, III, and IV by digital X-ray radiogrammetry (DXR). METHODS: We took X-rays of the bones of a cadaveric left hand which were immobilized in a wooden cradle to preserve an approximate in vivo configuration. The X-rays were digitized into Digital Imaging and Communications in Medicine (DICOM) files which were analyzed using dxr-online (dxr-online, Sectra, Sweden) which uses the same DXR-BMD algorithm previously used by Pronosco X-posure v2 and Sectra Osteoporosis package. The X-rays were repeated four times. We then surrounded the bones with a layer of lard, and again X-rayed four times. This process was repeated with the bones were covered by two layers, and then three layers of lard. RESULTS: The measured DXR-BMD increased by a maximum of 0.44% when the metacarpals were covered by either two or three layers of lard compared with when the metacarpals were not covered by lard. CONCLUSION: The measurement of metacarpal BMD measured by DXR is minimally affected by surrounding lard. The measurement of metacarpal BMD by DXR seems to be a way of avoiding the artifactual change in BMD caused by fat, when it is measured by DXA.
OBJECTIVE: To assess the effects of a language-sensitive diabetes education program on dietary changes and plasma lipid profiles. METHOD: Hispanic participants (n=13 males and 18 females, mean age = 54.00 + 10.68 years) participated in a 3-month health education study. Spearman correlation coefficients were used to evaluate correlations between dietary intake and laboratory measurements. RESULTS: There were significant decreases in serum total cholesterol (-16.07 mg/dl, P= 0.035), HDL cholesterol (-3.23 mg/dl, P = 0.01), LDL cholesterol (-11.71 mg/dl, P = 0.013) and dietary cholesterol (-79.22 mg, P = 0.03). No significant mean change was observed in triglyceride and total cholesterol/HDL ratio. There was also a reduction in body mass index (BMI) (-0.15 kg/m(2), P = 0.40), fasting glucose (-3.90 mg/dl, P = 0.43) and dual energy X-ray absorptiometry (DXA) total fat (-0.50, P = 0.97). Although not statistically significant, saturated fatty acids (-4.90 g, P = 0.19), polyunsaturated fatty acids (-3.31g, P = 0.11), and carbohydrate (-44.82 g, P = 0.22), decreased after three months. CONCLUSION: There were significant improvements in dietary intake and serum lipids after a three-month culture-specific diabetes education program.
OBJECTIVES: Diabetes mellitus and obesity are prevalent in the Hispanic community. This group has not benefited greatly from diabetes interventions due to cultural, language and financial constraints. We designed a prospective cohort study to determine the clinical impact on adiposity and glycemic control in Hispanics with type 2 diabetes. RESEARCH DESIGN AND METHODS: The program conducted in Spanish by a multidisciplinary team of health care providers focused on improving glycemic control and complications through cultural lifestyle changes. Outcomes were changes in glycemic control by fasting insulin, glucose and HbA1c, body composition and selected adipokines, adiponectin, leptin and ghrelin. Body composition was measured by dual energy x-ray absorptiometry. Changes from baseline at three months were compared using paired t-tests and with Spearman's correlations. RESULTS: Glycemic control improved by HbA1c (7.9% ± 2.0% vs 7.1% ± 1.7%; P = <0.001), and fasting glucose (166.4 ± 66.0 mg/dl vs 143.2 ± 57.9 mg/dl; P = 0.003). Body weight (81.3 ± 17.9 kg vs 80.3 ± 18.0 kg; P = 0.002), waist circumference (101.6 ± 13.4 cm vs 99.1 ± 12.7 cm; P = 0.015), and truncal fat (16.5 ± 5.7 kg vs 15.9 ± 5.6 kg; P = 0.001) decreased. Only leptin (19.6 ± 15.0 ng/ml vs 16.3 ± 12.7 ng/ml; P = 0.002) was reduced and related to change in body weight (r = 0.392; P = 0.022). CONCLUSIONS: Our program significantly improved glycemic control and decreased obesity in diabetic Hispanic subjects. The early benefits on glycemic control may be related to reductions in leptin through loss of adipose tissue. Success in impacting diabetes and related complications can occur in a culturally focused and multidisciplinary context.
Diabetes mellitus continues to be a heavy burden on health and health resources throughout the world. In the USA the burden is borne disproportionately by ethnic minorities such as Hispanics. Therefore health education for Hispanics is important and it can help reduce the incidence of diabetes among Hispanics in the USA.
A study was conducted to appraise a new EchoMRI™ device for body composition analysis (BCA) of infants and to compare it with dual energy X-ray absorptiometry (DXA), using chemical analysis as a reference method.The calibration part of the study included cross-validation comparisons between EchoMRI™ measurements of awake, anesthetized and dead piglets of the calibration set. It also included comparison of two different approaches to refining the calibration of EchoMRI™, by low- or by high-dimensional linear regressions. Only the low-dimensional approach was applied to DXA.The validation part yielded EchoMRI™ accuracy of 27 g and 70 g for fat and total water, respectively, on piglets scanned while anesthetized, as compared with 24 g and 57 g, respectively, for DXA.EchoMRI™ precision was found to be 4 g and 7 g for fat and total water, respectively, for anesthetized piglets, as compared to 16 g and 14 g, respectively, for DXA. The differences between fat measurements of awake, anesthetized and dead piglets can be statistically significant, but are comparable in magnitude to random errors.To summarize: Characterization of random errors by CV, especially that of fat, is not suitable for BCA, whereas absolute errors or errors relative to total body weight can be applicable. Low- and high-dimensional regressions offer nearly the same accuracy improvements. Improved DXA and EchoMRI™ offer nearly the same accuracy, within 1% of weight in fat, while EchoMRI™ has better precision, within 0.2 % of weight in fat for anesthetized and dead piglets as compared to DXA's 0.5-0.6%.
OBJECTIVE: Bioelectrical impedance analysis (BIA) of hydration and body composition has made significant progress during the past 3 decades. With the development of Bioimpedance spectroscopy (BIS), bioimpedance has been expanded to reliably predict extracellular fluid (ECF) and total body water (TBW), allowing the calculation of fat-free mass (FFM) and fat mass (FM). In this study, a new BIS device (ImpediVet™), designed for body composition measurements in animals, was assessed for precision and accuracy in measuring TBW, FFM and FM in rats. METHODS: In a validation study, 25 rats were measured for body composition (TBW, FFM and FM) using BIS and chemical carcass analysis (CCA). BIS precision was assessed by the coefficient of variation using multiple BIS readings, while BIS accuracy was assessed by regression analysis of BIS and CCA values for each body compartment. In a cross-validation study, prediction equations generated from the validation group for TBW, FFM and FM were applied to an independent cohort of 25 rats that were measured by BIS and CCA. Linear regression analysis and paired t-tests were used to assess significance of relationships and measurement differences within groups. RESULTS: In the validation study, BIS was highly correlated with CCA for TBW (r(2)=0.988), FFM (r(2)=0.987) and FM (r(2)=0.966). Even so, BIS significantly underestimated TBW (mean: -31.07 g, -13.3%, p<0.001) and FFM (-50.69 g, -15.5%, p<0.001), while overestimating FM (+65.75 g, +63.5%, p<0.001). In the independent, cross-validation group of rats the prediction equations accurately predicted carcass values for TBW (-0.2%, p=0.350), FFM (-0.2%, p=0.457) and FM (+1.5%, p=0.508). CONCLUSION: Based on these results, BIS provided a precise and accurate means to determine in vivo body composition in rats.
