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At least 19 recordsLinked to original sources
PubMed1999

Fat mass in infants and toddlers: comparability of total body water, total body potassium, total body electrical conductivity, and dual-energy X-ray absorptiometry.

BACKGROUND: Accurate assessment of body composition in infants and children is fundamental to understanding normal growth and development. Validation of methods applicable to pediatric populations is needed. In the absence of a gold standard, this study was conducted to compare methods using total body water, total body potassium, total body electrical conductivity, and dual-energy x-ray absorptiometry measurements for the estimation of body fat mass in infants and toddlers. METHODS: Repeated body composition measurements were performed on 76 healthy term infants at 0.5, 3, 6, 9, 12, 18, and 24 months of age. Total body water was determined by deuterium dilution and converted to fat-free mass. Total body electrical conductivity was used to measure fat mass. Total body potassium was estimated by whole-body counting and converted to fat-free mass. Dual-energy x-ray absorptiometry was used to estimate fat mass at 0.5, 12, and 24 months only. Data were analyzed by repeated measures analysis of variance, followed by Bonferroni multiple comparisons at 5%. RESULTS: Significant differences among methods were encountered at each age (p = 0.001-0.05). The rank order of the methods and the magnitude of the method differences were a function of age, not of gender or infant feeding mode. Wide limits of agreement imply that the methods are not interchangeable for group or individual measurements. CONCLUSIONS: Methods using total body water, total body potassium, total body electrical conductivity, and dual-energy x-ray absorptiometry to estimate body fat mass in infants and toddlers are not interchangeable and require further development and validation.

Absorptiometry, Photon↗
PubMed1992

The prediction of total body water from body impedance in young obese subjects.

Almost all formulae for the prediction of total body water (TBW) from body impedance are based on the assumption of a constant conductor configuration--i.e. a constant subject section. In this paper we report on data obtained for a group of 19 young obese subjects (relative weight greater than 120%) and 10 young normal subjects (relative weight 80-110%). In obese subjects, the application of two different formulae generated from normal children gave biased results and led to an underestimation of TBW with respect to the reference value obtained by deuterium oxide dilution. Body mass index accounted for more than 40% of the inter-individual variability, suggesting that body size was not taken sufficiently into consideration by the predictive formulae used. We have used the body surface area as the anthropometrical parameter for the prediction of TBW from body impedance. The regression formula that we propose (TBW = 1.156 x (surface area/body impedance) - 2.356; R = 0.96), although requiring further validation on external populations, seems to provide a more realistic assessment of TBW in young obese subjects. We therefore suggest that the assessment of TBW in young obese subjects requires specifically designed prediction formulae.

Adolescent↗
PubMed2006

A novel method to determine lean body water using localized skin biopsies: correlation between lean skin water and lean body water in an overhydration model.

To determine the relationship between total body water (TBW) fraction and local water content measured in the skin (SW) this study assessed eight anesthetized piglets in an overhydration model. TBW was assessed by deuterium oxide dilution and body mass measurements taken throughout the experiments, and by whole body carcass analysis at the end of each experiment. Additionally, extracellular water and plasma volume were assessed using bromide dilution and Evan's blue dilution, respectively. SW was assessed by tissue biopsies taken at 60-min intervals throughout the experiment. Lean body water (LBW) fraction and lean skin water (LSW) fraction were assessed by extracting the fat from the carcass and biopsy samples. A correlation does exist between TBW fraction and SW fraction with r2=0.58 (P<0.05); however, the strongest correlation occurred between the LBW fraction and LSW fraction with r2=0.87 (P<0.05) and an SE of prediction of 0.77%. These data demonstrate that LSW gives an accurate and precise estimate of LBW and could therefore be used to determine the hydration index in appropriate research settings.

Animals↗
PubMed1997

Total body water and body composition in chronic peritoneal dialysis patients.

In this investigation, total body water (TBW) in ten chronic peritoneal dialysis patients was studied by deuterium (TBW-2H), skinfold thickness (TBW-ST), Watson formula (TBW-WA), 58% of body weight (TBW-58%), and bioelectrical impedance (TBW-BIA), and these results were compared with the reference oxygen18 (TBW-18O) method. We also analyzed the fat-free mass (FFM) by skinfold thickness (FFM-ST), bioelectrical impedance (FFM-BIA), oxygen18 (FFM-18O), and creatinine kinetics method (FFM-CK). In addition, resting metabolic rate was measured by indirect calorimetry. Compared with TBW-18O, TBW-58% and TBW-BIA were significantly different (P < 0.01). TBW-2H overestimated TBW-18O by 4.3%. TBW-ST and TBW-WA gave slightly greater values than TBW-18O, although these values were nonstatistically significant. The best prediction of total body water from these methods was obtained with the Watson formula. When Kt/V was calculated from these results, the values obtained were statistically greater (BIA, P < 0.001) and smaller (58% BW, P < 0.01) than those obtained with either 18O or Watson formula. The fat-free mass estimation also led to discrepant findings. Indeed, FFM-CK was significantly lower (P < 0.05) as compared with FFM-ST, FFM-BIA, or FFM-18O. Resting metabolic rate was strongly correlated with FFM estimated by skinfold thickness (r = 0.91, P < 0.001), bioelectrical impedance (r = 0.85, P < 0.005), and 18O (r = 0.77, P < 0.01), but not when fat-free mass was estimated by the creatinine kinetic method. The water content of fat-free mass estimated by skinfold thickness was found to be 69.7 +/- 6.9% in these patients, a value lower than the standard 73.2% found in healthy adults. This study confirms that there is an abnormal water distribution in chronic peritoneal dialysis patients. However, when compared with the oxygen18 reference method, the Watson formula allows a reliable estimation of Kt/V.

Aged↗
PubMed1980

Body composition. Prediction of normal body potassium, body water and body fat in adults on the basis of body height, body weight and age.

In 134 males and 242 females, aged 20-70 years, most of them randomly selected from population studies, the body composition was estimated from the measurements of body height (BH), body weight (BW), total body potassium (TBK) and total body water (TBW). TBK was measured with isotope dilution technique using 42K or determined as 40K in a whole body counter. TBW was determined with an isotope dilution technique using tritiated water, assayed in urine or plasma. From these data, body cell mass (BCM), intra- and extra-cellular water (ICW and ECW, resp.) and body fat (BF) were calculated for each individual. Significant correlations were found between age versus TBK, ECW, BF and ECW/ICW; between BW versus TBK, TBW, ECW, BF and ECW/ICW; (females only) and between BH versus TBK, TBW, ECW (females only) and ECW/ICW. For the prediction of TBK, TBW and BF, multiple regression equations based on BW, BH and age are given. These equations are also presented diagrammatically. The problems with the methods used are considered as well as the applicability of the formulas for the calculation of BCM etc. The predictive value of the results when both TBW and TBK are used for the calculation of body composition data is discussed and compared with similar results, based on TBW or TBK only. It is concluded, that the most reliable method for calculation of BF is to estimate both TBW and TBK.

Adult↗
PubMed1995

Assessing total body protein, mineral, and bone mineral content from total body water and body density.

We hypothesized that investigators could assess bone mineral content (BMC), total body mineral (M), and protein (P) from body water (W) and density (DB) based on the theory of W. E. Siri (Advances in Biological and Medical Physics, 1956, p. 239-280 and Techniques for Measuring Body Composition, 1961, p. 223-224) for body composition analysis. Siri used one or more of the body components and the densities of the body, fat (F), W, M, and P to estimate one of the remaining fractional masses. We compared M, BMC, P. F, and fat-free mass (FFM) in 31 subjects (15 women and 16 men) computed from measurements of W and DB with [4-compartment (4C) model] and without [3-compartment (3C) model] BMC (from dual X-ray absorptiometry). 4C model P was calculated by difference (P = FFM - W - M). Mean difference (P > 0.05) ranged from 0.1 to 0.8%. Correlations [+/- standard error of estimate (%)] between 4C and 3C model values were significant (r = 0.907 +/- 8.8, 0.907 +/- 8.7, 0.969 +/- 6.6, 0.998 +/- 2.0, and 0.999 +/- 0.7% for M, BMC, P, F, and FFM, respectively). We concluded that investigators can assess M, BMC, and P from W and DB.

Adult↗
PubMed1995

Multi-frequency impedance for the prediction of extracellular water and total body water.

The relationship between total body water (TBW) and extracellular water (ECW), measured by deuterium oxide dilution and bromide dilution respectively, and impedance and impedance index (height2/impedance) at 1, 5, 50 and 100 kHz was studied. After correction for TBW, ECW was correlated only with the impedance index at 1 and 5 kHz. After correction for ECW, TBW was best correlated with the impedance index at 100 kHz. The correlation of body-water compartments with impedance values obtained with modelling programs was lower than with measured impedance values. Prediction formulas for ECW (at 1 and 5 kHz) and TBW (at 50 and 100 kHz) were developed. The prediction errors for ECW and TBW were 1.0 and 1.7 kg respectively (coefficient of variation 5%). The residuals of both ECW and TBW were related to the ECW/TBW value. Application of the prediction formulas in a population, independently measured, revealed a slight overestimation of TBW and ECW, which could be largely explained by differences in the validation group in body-water distribution and in body build. The ratio of impedance at 1 kHz to impedance at 100 kHz was correlated with body-water distribution (ECW/TBW). The relation is however not strong enough to be useful as a predictor. It is concluded that an independent prediction of ECW and TBW, using impedance at low and high frequency respectively, is possible, but that the bias depends on the body-water distribution and body build of the measured subject.

Adult↗
PubMed1990

Comparison of estimates of fat-free mass in normal and obese women from measurements of body potassium, body water and body density.

The relation between the estimates of fat-free mass (FFM) obtained from measurements of density, total body potassium and water was investigated in 104 women with Quetelet's Index between 19.9 and 49.7 kg/m2, body weight between 42.3 and 133.5 kg. The mean difference between the estimates based on water and potassium, previously reported as 2.2 kg or 4.4 per cent, was found to be independent of Quetelet's Index. The mean difference (s.e.m.) between the estimates of FFM based on density, compared with the average values from water and potassium, was found to be +7.0 (1.0), +6.3 (0.7) and +7.4 (1.1) kg in the ranges of Quetelet's Index 19.9-30.0, 30.1-40.0, and 40.1-49.7, respectively. The relative independence on Quetelet's Index of the difference between the estimates based on density compared with (water + potassium) is consistent with the idea that tissues of a higher density (ie, skin and bone) make up a larger proportion of the fat-free body weight in thin subjects than in fat ones.

Adult↗
PubMed1998

Physical fitness influences water turnover and body water changes during trekking.

PURPOSE: This study was performed to assess water turnover and changes of body water during a trekking tour at moderate altitude. METHODS: Fifteen healthy normally trained adults participated in a 7-d backpack trek tour in the Swiss Alps (total walking distance: 120.5 km; cumulated altitude difference: 6990 m (uphill) and 7550 m downhill; lowest point: 1285 m; highest point: 3317 m). Total body water and water turnover were measured using deuterium dilution and elimination (oral load of 0.33 g 99.8% D2O per kg body weight, overnight equilibration period, pre- and postdose saliva samples immediately before and after sleep, analysis of D2O concentrations in saliva using Fourier-transform infrared spectroscopy, CV < 1%). Physical training state was assessed after the tour using the lactate-exercise intensity relationship obtained by performing 50-W increments every 3 min on a cycle ergometer. RESULTS: Body water decreased from the evening of day 0 to the evening of day 4 (from 45.3 +/- 7.3 L to 43.4 +/- 7.6 L, P < 0.05), and did not significantly decrease (43.5 +/- 7.9 L) until the evening of day 5 (maximum of trekking exercise intensity). Mean daily water turnover was 5.7 +/- 1.8 L x d(-1) corresponding to 78.7 +/- 17.5 mL x kg(-1) x d(-1). Body water changes and water turnover were significantly related to the exercise intensity obtained at the lactate threshold as well as at the level of 4 mM lactate. CONCLUSIONS: This correlation may be in part explained by differing glycogen content of muscle tissue.

Adult↗
PubMed1982

Total body water and total body potassium in patients with continent ileostomies.

Total body water and total body potassium were studied in 14 patients submitted to proctocolectomy six to 10 years after they had been provided with a continent ileostomy. Total body water was determined with an isotope dilution technique using tritiated water as a tracer. Total body potassium was determined by counting the gamma radiation from the naturally present nuclid 40K in a total body counter. The results were compared with 'normal values' produced by multiple regression analysis of data from 476 healthy controls which had been published earlier from the same laboratory. The investigations showed no signs of water or potassium depletion in patients with continent ileostomies.

Adult↗