Is the Impedance index (ht2/R) significant in predicting total body water?

Kushner, Robert F.; Schoeller, Dale A.; Fjeld, Carla R.; Danford, Lynn C.

doi:10.1093/ajcn/56.5.835

Cited by 343 publications

(307 citation statements)

References 14 publications

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“…Nitrogen balance studies were conducted during days 3 to 7 [19,20]. Body composition was assessed by bioelectrical impedance analysis (RJL-101A Systems, Detroit, MI, USA) with equations validated for lean [21], obese [22] and elderly [23] subjects.…”

Section: Subjects Materials and Methodsmentioning

confidence: 99%

Elevations of plasma methylarginines in obesity and ageing are related to insulin sensitivity and rates of protein turnover

et al. 2005

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Elevations of plasma methylarginines in obesity and ageing are related to insulin sensitivity and rates of protein turnover Abstract Aims/hypothesis: Increased circulating methylarginines (MA) have been linked to the metabolic syndrome to explain endothelial dysfunction and cardiovascular disease risk. Proteins that contain MA are regulatory and release them during catabolism. We hypothesised that increased protein turnover in insulin-resistant states contributes to an increase in circulating MA. Materials and methods: We performed hyperinsulinaemic, euglycaemic, and isoaminoacidaemic experiments on 49 lean, obese and elderly subjects, with measurements of the kinetics of glucose and protein metabolism. Plasma MA, i.e. asymmetrical dimethylarginine (ADMA), symmetrical dimethylarginine (SDMA), and N G -monomethyl-L-arginine (NMMA), lipids and body composition were measured. Results: Insulin resistance of glucose and protein metabolism occurred in obese and elderly subjects. ADMA concentrations were 29 to 120% higher in obese and 34% higher in elderly than in lean subjects. SDMA were 34 and 20% higher in obese than in lean and than in elderly subjects, respectively. NMMA were 32% higher in obese than in lean subjects. ADMA differed by sex, being higher in men, namely by 1.75× in obese men and by 1.27× in elderly men. Postabsorptive ADMA (r=0.71), SDMA (r=0.46), and NMMA (r=0.31) correlated (all p<0.05) with rates of protein flux. All three MA correlated negatively with clamp glucose infusion rates and uptake (p<0.001). ADMA and SDMA correlated negatively with net protein synthesis and clamp amino acid infusion rates (p<0.05). All MA also correlated with adiposity indices and fasting insulin and triglycerides (p<0.05). Conclusions/ interpretation: Obesity, sex and ageing affect MA. Elevations of the three MA in obese, and of ADMA in elderly men, are related to increased protein turnover and to lesser insulin sensitivity of protein metabolism. These interrelationships might amplify insulin resistance and endothelial dysfunction.

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Section: Subjects Materials and Methodsmentioning

confidence: 99%

Elevations of plasma methylarginines in obesity and ageing are related to insulin sensitivity and rates of protein turnover

et al. 2005

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“…FFM was further calculated directly from the impedance index (ZI) as described by Kushner et al 23 . The ZI was then used to calculate FFM, using three different equations [1][2][3] that were derived from children with a similar age range as our study group (Table 1).…”

Section: Body Compositionmentioning

confidence: 99%

A Bedside Measure of Body Composition in Duchenne Muscular Dystrophy

Elliott

Davidson

Davies

et al. 2015

Pediatric Neurology

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Introduction:In clinical practice, monitoring body composition is a critical component of nutritional assessment and weight management in boys with Duchene muscular dystrophy (DMD). We aimed to evaluate the accuracy of a simple bedside measurement tool for body composition, namely bioelectrical impedance analysis (BIA), in boys with DMD. Methods:Measures of fat free mass (FFM) were determined using a BIA machine and compared against estimations obtained from a reference body composition model. Additionally, the use of raw impedance values were analysed using three existing predictive equations 1-3 for the estimation of FFM. Accuracy of BIA was assessed by comparison against the reference model by calculation of biases and limits of agreement.Results: Body composition was measured in ten boys with DMD, mean age 9.01 ± 2.34 years. The BIA machine values of FFM were on average 2.3 ± 14.1 kg higher than reference values. Limits of agreement (based on 95 % CI of the mean) were -7.4 to 2.9 kg. There was a significant correlation between the mean FFM and difference in FFM between the BIA machine and the reference model (r = -0.86, p= 0.02) suggesting that the bias was not consistent across the range of measurements. The most accurate predictive equation for the estimation of FFM using raw impedance values was Pietrobelli's 3 ; mean difference -0.7 kg, 95 % limits of agreement (-3.5 to 2.0 kg). Conclusion:In a clinical setting, where a rapid assessment of body composition is advantageous, the use of raw impedance values, combined with the Pietrobelli 3 equation, is recommended for the accurate estimation of FFM, in boys with DMD.

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“…18 Assumed densities of the four components were accounted for when Treatment of BIA data BIA data are usually expressed in the form HT 2 /R and then used to predict TBW. 17 This approach assumes that the body represents a single cylinder of conductive (water-containing) tissue. Impedance of that cylinder to an electrical current is proportional to cylinder length and volume, hence adjustment of R for HT (acting as a proxy for cylinder length) allows estimation of cylinder volume.…”

Section: C Modelmentioning

confidence: 99%

A simplified approach to analysing bio-electrical impedance data in epidemiological surveys

et al. 2006

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Background: Bio-electrical impedance analysis (BIA) is widely used to estimate body composition. It is simple, quick and cheap, but less accurate than other methods. It has potential epidemiological value, but has conventionally required validation before application. Aims: To develop a simple method of expressing weight, height and impedance data that avoids the need for populationspecific validation equations in order to facilitate epidemiological application. Methods: Body composition was measured using the four-component model in young adults (43 males, 90 females). Impedance (R) was measured hand-foot and foot-foot. Lean mass and fat mass were adjusted for height to give lean mass index (LMI) and fat mass index (FMI). Based on theoretical principles, we generated the index 1/R, which provides an index of body water adjusted for height. Sex-specific regression models were used to investigate the relationships between (a) 1/R and LMI, and (b) body mass index (BMI) adjusted for 1/R and FMI. The success of this approach was evaluated in relation to the conventional BIA approach, using correlation analysis. Results: 1/R was a highly significant predictor of LMI. BMI adjusted for 1/R was a significant predictor of FMI. Our approach performed as well as the conventional approach for LMI, but not for FMI. Discussion: Direct use of BIA data, rather than their combination with population-specific equations for the prediction of total body water, proved successful at ranking individuals of both sexes in terms of LMI and FMI. The index 1/R may prove particularly valuable in epidemiological studies where ranking of LMI is required.

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Is the Impedance index (ht2/R) significant in predicting total body water?

Cited by 343 publications

References 14 publications

Elevations of plasma methylarginines in obesity and ageing are related to insulin sensitivity and rates of protein turnover

Elevations of plasma methylarginines in obesity and ageing are related to insulin sensitivity and rates of protein turnover

A Bedside Measure of Body Composition in Duchenne Muscular Dystrophy

A simplified approach to analysing bio-electrical impedance data in epidemiological surveys

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