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A whole-body model to distinguish excess fluid from the hydration of major body tissues^1,2,3

¹ From the Research and Development department, Fresenius Medical Care, Bad Homburg, Germany (PWC, PW, and UMM); the Institut für Humanernährung und Lebensmittelkunde, Christian Albrechts-Universität, Kiel, Germany (MJM, AB-W, and OK); and the MRC Childhood Nutrition Research Centre, Institute of Child Health, London, United Kingdom (NJF)

² Data from the Institut für Humanernährung und Lebensmittelkunde were obtained through funding from Fresenius Medical Care.

³ Reprints not available. Address correspondence to PW Chamney, Research and Development, Fresenius Medical Care, Bad Homburg, Germany.

	ABSTRACT

TOP ABSTRACT INTRODUCTION SUBJECTS AND METHODS RESULTS DISCUSSION APPENDIX A APPENDIX B APPENDIX C REFERENCES

 
Background: Excess fluid (ExF) accumulates in the body in many conditions. Currently, there is no consensus regarding methods that adequately distinguish ExF from fat-free mass.

Objective: The aim was to develop a model to determine fixed hydration constants of primary body tissues enabling ExF to be calculated from whole-body measurements of weight, intracellular water (ICW_WB), and extracellular water (ECW_WB).

Design: Total body water (TBW) and ECW_WB were determined in 104 healthy subjects by using deuterium and NaBr dilution techniques, respectively. Body fat was estimated by using a reference 4-component model, dual-energy X-ray absorptiometry, and air-displacement plethysmography. The model considered 3 compartments: normally hydrated lean tissue (NH_LT), normally hydrated adipose tissue (NH_AT), and ExF. Hydration fractions (HF) of NH_LT and NH_AT were obtained assuming zero ExF within the diverse healthy population studied.

Results: The HF of NH_LT mass was 0.703 ± 0.009 with an ECW component of 0.266 ± 0.007. The HF of NH_AT mass was 0.197 ± 0.042 with an ECW component of 0.127 ± 0.015. The ratio of ECW to ICW in NH_LT was 0.63 compared with 1.88 in NH_AT. ExF can be estimated with a precision of 0.5 kg.

Conclusions: To calculate ExF over a wide range of body compositions, it is important that the model takes into account the different ratios of ECW to ICW in NH_LT and NH_AT. This eliminates the need for adult age and sex inputs into the model presented. Quantification of ExF will be beneficial in the guidance of treatment strategies to control ExF in the clinical setting.

Key Words: Excess fluid • tissue hydration • normal hydration • body composition • adipose tissue • ECW:ICW ratio

	INTRODUCTION

TOP ABSTRACT INTRODUCTION SUBJECTS AND METHODS RESULTS DISCUSSION APPENDIX A APPENDIX B APPENDIX C REFERENCES

 
Diseases such as cardiac impairment and kidney failure often lead to an accumulation of excess fluid (ExF), increasing the body's state of hydration. ExF may be regarded as an expansion of the extracellular or total body fluid compartments of the body but is not required by the body to maintain homeostasis. In patients with kidney failure, it is essential to remove the ExF to avoid long-term cardiovascular mortality (1-4). Despite the occurrence of ExF, little progress has been made in the body-composition field to develop a method for its identification.

Well-established techniques, such as hydrometry (5, 6), dual-energy X-ray absorptiometry (DXA) (7-9), and underwater weighing (10, 11), are available to obtain estimates of fat-free mass (FFM). The major drawback with these methods, however, is that ExF cannot be distinguished from FFM. Although ExF may be reflected by a rise in ECW (12) or TBW, quantification of ExF is only possible once a hydration reference has been established. The hydration reference represents normal values of ECW and TBW found in healthy control subjects, although the proportions of ECW and TBW vary according to body composition. Where body composition is assumed constant in a given subject group, a hydration reference may be established allowing ExF to be calculated (13). The ratio of ECW to TBW also offers the basis of a hydration reference, and this approach has been applied in patients with corrections for age (14). The hydration of FFM (H_FFM), although regarded constant at 0.73 (15), may be influenced by several health factors (16) thus limiting its use for quantification of ExF. Additionally, in more recent work, the hydration of lean soft tissue and its relation with the ratio of ECW to ICW was investigated (17).

One factor influencing the ratio of ECW to ICW (and hence its use as a reference) is the diversity of major body tissues such as the distinct adipose tissue and lean (nonadipose) tissue (18-20). To take into account the dissimilar hydration of relevant tissues and satisfy the need for a method to quantify ExF, we developed a new body-composition model.

	SUBJECTS AND METHODS

TOP ABSTRACT INTRODUCTION SUBJECTS AND METHODS RESULTS DISCUSSION APPENDIX A APPENDIX B APPENDIX C REFERENCES

 
Subjects and measurements
Data were used from 89 healthy adults recruited in Kiel, Germany. These data were supplemented with those from 15 healthy adults gathered in a previous study conducted in Cambridge United Kingdom (Morgan M, Madden A, Jennings G, Elia M, Fuller N, unpublished observations). Ethical approval was obtained from the ethical board of the Christians Albrechts Universität. The subjects were specifically chosen such that the full extent of the body composition range (in terms of percentage fat) could be investigated. The subject characteristics derived by combining the data (n = 104) from the 2 centers are reported in Table 1.

(1)

where M_{Br_Dose} is the mass (in mmol) of bromide administered and C_{Br_4 h} and C_{Br_Baseline} are the concentrations (in mmol/L) of bromide after the 4-h equilibration period and at baseline, respectively. The factor 0.9 compensates for a small leakage of bromide into the intracellular space, and the factor 0.95 accounts for Donnan equilibrium effects. In the Cambridge data, ECW was determined by using a spectrophotometric fluorescein method with deproteinization. The assay was automated by using Cobas Fara (Roche Diagnostic, Welwyn Garden City, United Kingdom). The appropriate corrections were then applied (23). Before any further analysis, the whole-body volumes of TBW and ECW were converted to mass by the density of water, D_BW, by using a value of 0.99371 kg/L at 36 °C (24).

Total body fat was measured by using DXA scanners (Hologic Inc, Waltham, Ma) models QDR-4500A V8.26a in Kiel and QDR-1000/W in Cambridge. Calculated values of body fat were also obtained from densitometry via Siri's equation (25) and by application of a 4-component (4-C) model (24) with the use of measurements of body volume obtained either by air-displacement plethysmography with a Bod-Pod (Life Measurement Instruments, Concord, CT) in Kiel or by underwater weighing in Cambridge. It was shown that these measurements of body volume are equivalent in healthy adults (26).

New 3-compartment model
Several authors have suggested that the body should be divided into adipose tissue (AT) and nonadipose body mass or adipose-free mass (AFM) (18-20, 27). The considerable disparity between the hydration of AT and AFM shown in these studies formed the basis of our new model. In the present study, it was assumed that in a state of health these 2 tissues could be considered "normally hydrated." A schematic of the new 3-component (3-C) tissue-based model is shown in Figure 1. It is consistent with the molecule level of the 5-level model classification described elsewhere (28), but modified to reflect the presence of excess fluid that may accumulate due to pathological reasons. It is clear from Figure 1 that the mass of ExF is a subcompartment of AFM. Therefore, to avoid ambiguity, AFM is divided into "normally hydrated lean tissue" (NH_LT) and M_ExF. Similarly, the term "normally hydrated adipose tissue" (NH_AT) is used in place of adipose tissue to emphasize how adipose tissue should be regarded. The hydration properties of NH_LT and NH_AT are the cornerstones of the new model that provide the hydration reference against which ExF may be expressed. When ExF is present it may reside within adipose tissue or lean tissue raising the hydration of the respective tissue above the "normal" values, eg, edema. Alternatively, ExF may simply appear as a distinct compartment without altering the hydration of the major tissues, eg, ascites. Regardless of how ExF is manifested, for the purposes of calculation it is convenient to consider ExF as a compartment separate from normally hydrated tissue as represented in Figure 1.

View larger version (57K): [in this window] [in a new window]   FIGURE 1. A: The new 3-compartment model comprising normally hydrated adipose tissue mass (MNH_AT), normally hydrated lean tissue mass (MNH_LT), and excess fluid mass (MExF). B: Relation between the compartments of the new model and standard measures of body composition in terms of lean mass, fat mass, and fat-free mass (FFM).

In contrast with the current model, an estimate of ExF can be obtained by considering the expansion of either ECW_WB or TBW_WB. These methods generally assume a fixed ratio, such as ECW_WB:ICW_WB, reflecting normal hydration status for a given population and are given in Table 2.

Appendix D

	RESULTS

TOP ABSTRACT INTRODUCTION SUBJECTS AND METHODS RESULTS DISCUSSION APPENDIX A APPENDIX B APPENDIX C REFERENCES

 
After normalization of fat, TBW, ECW_WB, and ICW_WB, a clear reduction in body water compartments was observed with increasing body fat content as shown in Figure 2. By linear regression of normalized TBW and ECW_WB, as defined by Equations C4 and C8 against DXA fat mass, the following parameters were obtained: a_TBW = –0.672, b_TBW = 0.703, a_ECW = –0.185, and b_ECW = 0.266. By using these regression parameters, the tissue hydration parameters were calculated with Equations C5, C9, C11, and C12. The process was repeated by using fat mass calculated with the Siri equation and the 4-C model. However, these particular methods are not entirely independent of either body weight or TBW and so a small degree of mathematical coupling occurs, which slightly influences bias. The hydration parameters obtained with all 3 methods for fat determination are shown in Table 3 along with those derived by using DXA for comparison. Literature values obtained with the use of in vitro techniques are shown in Table 4. By substitution of the DXA hydration parameters given in Table 3 into Equation B5, the expression for the mass of ExF may be reduced to the following:

(2)

Similarly, the mass of NH_LT given by Equation B2 may be simplified to the following:

(3)

Rearrangement of Equation A1 leads to the mass of NH_AT, as follows:

(4)

Finally, by combining the parameters H_{TW_NH_LT} and K_AR from Equation A8, the fat mass may be determined as follows:

(5)

By using the parameters a_TBW, b_TBW, a_ECW, and b_ECW from the regression analysis, Equations C4 and C8 were denormalized to yield 17.2 L ECW_WB and 24.7 L ICW_WB for a reference man of 73-kg body weight and 14.6-kg fat mass. Under these conditions, input measurement errors (SDs) of 0.5 kg, 1 kg, and 0.1 kg were estimated for ECW_WB, ICW_WB, and M_WB respectively. By propagation of these errors, the overall precision of the new method for calculation of M_ExF (Equation B5) was thus found to be 0.5 kg.

View larger version (38K): [in this window] [in a new window]   FIGURE 2. Relation of total body water (TBW), whole-body extracellular water (ECWWB), and whole-body intracellular water (ICWWB) with percentage fat measured by using dual-energy X-ray absorptiometry (DXA). A decline in normalized fluid volumes (NECW, normalized ECW; NICW, normalized ICW; and NTBW, normalized TBW) is observed after normalization of fluid volumes and fat mass to body weight as the proportion of body fat increases. The offsets of each regression line, where normalized fat = 0, reflect the total water, ECW, and ICW properties of normally hydrated lean tissue as indicated by HTW_NH_LT, HECW_NH_LT, and HICW_NH_LT, respectively. The slope of the regression lines for TBW and ECW are annotated with aTBW and aECW, respectively, from which total water, ECW, and ICW properties of normally hydrated adipose tissue (HTW_NH_AT, HECW_NH_AT, and HICW_NH_AT, respectively) can be obtained.

Figure 3

View larger version (26K): [in this window] [in a new window]   FIGURE 3. Comparison of hydration of fat-free mass (HFFM) and the ratios of whole-body extracellular water (ECWWB) to whole-body intracellular water (ICWWB) and ECWWB to total body water (TBW) in lean, normal, and obese subgroups. The boxes in each subgroup represent the interquartile range (50% of data) about the median value. The minimum and maximum values occurring within 1.5 times the interquartile range from the box edges are indicated by whiskers, and values falling outside this range (outliers) are represented by crosses. The notches in the boxes provide the 95% CIs. If the notches between any pair of boxes do not overlap, the difference between the subgroups is statistically significant. In this case, significant differences in the ECWWB:ICWWB and ECWWB:TBW occured between the lean and obese subgroups.

Table 5

Table 6

	DISCUSSION

TOP ABSTRACT INTRODUCTION SUBJECTS AND METHODS RESULTS DISCUSSION APPENDIX A APPENDIX B APPENDIX C REFERENCES

Although Morse and Soeldner (20) observed no difference in the hydration of NH_AT between obese and nonobese subjects, as seen in Table 4, a more recent study by Martin et al (33) indicated the contrary. This suggests that more detailed investigation of the hydration properties of adipose tissue may be necessary in differing degrees of obesity, not only in terms of total water content but also in terms of intra- and extracellular phases. The model developed in the present study assumed fixed hydration parameters for adipose tissue, and Figure 2 indicates that this serves as a good approximation to the measured data. Furthermore, an improvement in the reproducibility of the measurement methods is necessary before a more complicated model of adipose tissue can be justified.

It is evident from Figure 2 that whereas the ECW_WB is clearly lower than the ICW_WB when NH_LT dominates body weight, the converse is observed as NH_AT becomes the principle body weight component. This would appear to be the basis of the relative expansion of ECW_WB in obese subjects observed in other studies (27). As the ratio of ECW to ICW in NH_AT is a least twice that of NH_LT, then the whole-body proportions of NH_LT and NH_AT would explain the significant differences in the ratios of ECW_WB to ICW_WB and ECW_WB to TBW between the lean and obese subjects, as shown by categorical divisions of body fat (Figure 3).

Although the fat content of female subjects tends to be higher than that of male subjects, as seen in Table 1, these differences are reflected in the relative proportions of NH_LT and NH_AT. Therefore, there was no need to differentiate by sex in our model, because body composition (in terms of fat content) is taken into account from the input measurements of ECW_WB, ICW_WB, and body weight. It is also unlikely that age contributes fundamentally to the ratio of ECW_WB to ICW_WB, but is simply due to the proportions of NH_LT and NH_AT, as suggested by Wang et al (19). It can be argued that age-associated increases in fatness may lead to a higher proportion of NH_AT.

In our study, the mean value of H_FFM was found to be 0.723, which is consistent with the findings of others (24, 34, 35). In circumstances where ExF accumulates, a rise in H_FFM can be expected (16), but the lack of sensitivity of H_FFM to variations in ExF has not been emphasized in past studies. This can be illustrated by considering, for example, a subject with 55 kg FFM and 40 L TBW, which leads to a H_FFM of 0.727. If this subject now gains 5 kg ExF, H_FFM rises to 0.750, a change of just 3%. It is clear that because ExF appears in both the FFM and the TBW, the effect of ExF largely cancels out in H_FFM. This renders H_FFM a poor choice for providing a reliable hydration reference against which any ExF can be detected.

A significant difference in the ECW_WB-to-ICW_WB and ECW_WB-to-TBW hydration ratios was observed between the lean and obese subgroups, as seen in Figure 3. A similar rise in ratio of ECW_WB to ICW_WB has been observed in other studies with increasing BMI (27) and with increasing age (36). Therefore, any method for estimation of ExF that assumes fixed ECW_WB-to-ICW_WB or ECW_WB-to-TBW values for the entire population will result in bias errors at extremes of relative fat, as shown in Table 5. In the method described by Lopot et al (14), such effects of body composition have been taken into account by introduction of corrections for age and sex in the ratio of ECW_WB to TBW.

Considerable quantities of ExF were found to be present on application of the new model in a previous study of malnourished patients (32), as seen in Table 6. These results are reasonable given the high ratios of ECW to ICW resulting in these subjects coupled with the observation that a significant decrease in the ratio of plasma volume to ECW occurred in the severely malnourished subgroup (32). Methods to obtain the mass of LT or FFM via DXA, for example, do not differentiate ExF from these tissues (37). If a large proportion of the LT or FFM is occupied by ExF, the estimated protein content of these tissues will be reduced. This could lead to ambiguous conclusions regarding nutritional status. In the new model, by contrast, the mass of NH_LT applies regardless of the degree of ExF presented; that is, removal or accumulation of large volumes of fluid do not change the mass of NH_LT. It is proposed, therefore, that estimation of NH_LT mass may offer a more reliable alternative to measures such as LBM and FFM in disease.

	APPENDIX A

TOP ABSTRACT INTRODUCTION SUBJECTS AND METHODS RESULTS DISCUSSION APPENDIX A APPENDIX B APPENDIX C REFERENCES

 
General model definitions
Whole-body mass (M_WB) is given by the sum of the 3 compartments, namely normally hydrated adipose tissue mass (M_{NH_AT}), normally hydrated lean tissue mass (M_{NH_LT}), and excess fluid (ExF) mass (M_ExF), as follows:

(EA1)

The total water (TW), intracellular water (ICW), and extracellular water (ECW) components of M_{NH_LT} and M_{NH_AT} are defined by Equations A2-A4 and A5-A7, respectively.

(EA2)

(EA3)

(EA4)

(EA5)

(EA6)

(EA7)

The fat mass (M_Fat) is related to the mass of normally hydrated adipose tissue (M_{NH_AT}) with equation A8:

(EA8)

where K_AR is the ratio of residual adipose components (solids, mainly protein and mineral) to M_{NH_AT} with a value of typically 0.05 (30, 33).

	APPENDIX B

TOP ABSTRACT INTRODUCTION SUBJECTS AND METHODS RESULTS DISCUSSION APPENDIX A APPENDIX B APPENDIX C REFERENCES

 
Calculation of excess fluid
The sum of the intracellular components of M_{NH_LT} and M_{NH_AT} yields ICW_WB, as given by Equation B1:

(EB1)

Introducing the intracellular water mass fraction of normally hydrated lean tissue (H_{ICW_NH_LT}), substituting M_{NH_AT} by Equation A1 and rearranging for the lean tissue mass M_{NH_LT} leads to the following equation:

(EB2)

By introducing relevant constants, the mass of excess water (M_ExW not to be confused with M_ExF) may be calculated as the difference between ECW_WB and the sum of the extracellular components of NH_AT and NH_LT. By substitution of H_{ECW_NH_LT} and H_{ECW_NH_AT} in the respective tissues then gives the following equation:

(EB3)

Because ExF contains dissolved proteins and minerals in addition to ExW, a factor H_ExF may be applied which denotes the ratio of the mass of excess water, M_ExW to the mass of excess fluid, M_ExF. A mean value for H_ExF of 0.98 was assumed in the current model as suggested by Wang et al (16). Introducing H_ExF to convert M_ExW to M_ExF and rewriting Equation B3 by re-expressing M_{NH_AT} from Equation B1 leads to the following equation:

(EB4)

Substituting the expression for M_{NH_LT} (Equation B2) into Equation B4 and rearranging for M_ExF yields the following equation:

(EB5)

where k is defined by the following:

(EB6)

	APPENDIX C

TOP ABSTRACT INTRODUCTION SUBJECTS AND METHODS RESULTS DISCUSSION APPENDIX A APPENDIX B APPENDIX C REFERENCES

 
Calculation of principal body-composition parameters
The purpose of the following derivation was to extract the principal body-composition parameters defined by Equations A2-A7. To proceed, it was assumed that the ExF in healthy control subjects has a mean value of zero, ie, M_ExF = 0. By introducing Equation A1, the mass of total body water, TBW, may be expressed as follows:

(EC1)

By rewriting Equation C1 in terms of measurable input quantities via Equations A1 and A8, with M_ExF = 0, then the following equation is obtained:

(EC2)

The normalized TBW and fat, N_TBW and N_Fat, respectively, are obtained by dividing Equation C2 by M_WB, which leads to the following equation:

(EC3)

By normalizing the measured M_Fat and TBW data to body weight, the following linear relation between N_Fat and N_TBW was readily derived from regression analysis:

(EC4)

where a_TBW and b_TBW are the regression coefficients. Because Equations C4 and C3 are equivalent expressions, the tissue parameters H_{TW_LT} and H_{TW_AT} could thus be solved by comparing coefficients, as follows:

(EC5)

(EC6)

H_{TW_NH_LT} and H_{TW_NH_AT} are obtained directly from Equations C5 and C6.

The ECW parameters were obtained in the same way by normalization of ECW_WB and M_Fat to body weight. Taking the form of Equation C3 and making appropriate substitutions leads to the following equation:

(EC7)

The equivalent regression equation involving ECW may be written as follows:

(EC8)

By comparing coefficients of Equation C8 with those of Equation C7, then we obtain the following equations:

(EC9)

(EC10)

H_{ECW_NH_LT} and H_{ECW_NH_AT} are obtained from Equations C9 and C10. Finally, the parameters H_{ICW_NH_LT} and H_{ICW_NH_AT} can be readily found with the following equations:

(EC11)

(EC12)

	ACKNOWLEDGMENTS

 
The authors thank M Morgan, M Elia, A Madden, and G Jennings for the use of their Cambridge data.

PWC and PW developed the concepts for excess fluid calculation and prepared the manuscript. UMM contributed to technical aspects of the data analysis. MJM organized the study in Kiel and made a number of recommendations to simplify the manuscript. AB-W and OK undertook the studies in Kiel, performed all of the measurement assays and provided valuable scientific support. NJF contributed to refinement of the concepts, and input for alterations to the draft manuscript. PWC, PW, and UMM are employed at the Research and Development department at Fresenius Medical Care. None of the other authors has a conflict of interest to disclose.

	REFERENCES

TOP ABSTRACT INTRODUCTION SUBJECTS AND METHODS RESULTS DISCUSSION APPENDIX A APPENDIX B APPENDIX C REFERENCES

 

1. Dorhout Mees EJ, Ozbasli C, Akcicek F. Cardiovascular disturbances in hemodialysis patients: the importance of volume overload. J Neph 1995; 8: 2:71–8.
2. Fagugli RM, Pasini P, Quintaliani G, et al. Association between extracellular water, left ventricular mass and hypertension in haemodialysis patients. Nephrol Dial Transplant 2003; 18: 2332–8.[Abstract/Free Full Text]
3. Katzarski KS, Charra B, Luik AJ, et al. Fluid state and blood pressure control in patients treated with long and short haemodialysis. Nephrol Dial Transplant 1999; 14: 369–75.[Abstract/Free Full Text]
4. Dionisio P, Valenti M, Bergia R, et al. Influence of the hydration state on blood pressure values in a group of patients on regular maintenance hemodialysis. Blood Purif 1997; 15: 25–33.[Medline]
5. Schloerb PR, Friis-Hansen BJ, Edelman IS, Solomon AK, Moore FD. The measurement of total body water in the human subject by deuterium oxide dilution; with a consideration of the dynamics of deuterium distribution. J Clin Invest 1950; 29: 1296–310.[Medline]
6. Schoeller DA. Isotope dilution methods. In: Bjorntorp P, Brodoff BN, eds. Obesity. New York, NY: Lippincott, 1991: 80–8.
7. Mazess RB, Barden HS, Bisek JP, Hanson J. Dual-energy X-ray absoptiometry for total-body and regional bone-mineral and soft-tissue composition. Am J Clin Nutr 1990; 51: 1106–12.[Abstract/Free Full Text]
8. Slosman DO, Casez JP, Pichard C, et al. Assessment of whole-body composition with dual-energy x-ray absorptiometry. Radiol 1992; 185: 593–8.
9. Fuller NJ, Laskey MA, Elia M. Assessment of the composition of major body regions by dual-energy x-ray absorptiometry (DEXA) with special reference to limb muscle mass. Clin Physiol 1992; 12: 253–66.[Medline]
10. Siri WE. The gross composition of the body. In: Tobias CA, Lawrence JH, eds. Advances in biological and medical physics (Vol. 4). New York, NY: Academic, 1956: 239–80.
11. Going SB. Densitometry. In: Roche AF, Heymsfield SB, Lohman TG, eds. Human body composition. Champaign, IL: Human Kinetics, 1996: 3–23.
12. Guyton AC, Manning RD. Dynamics of fluid distribution between the blood and interstitium during overhydration. Am J Physiol 1980; 238: H645–51.[Medline]
13. Chamney PW, Kraemer M, Rode C, Kleinekofort W. A new technique for establishing dry weight in hemodialysis patients via whole body bioimpedance. Kid Int 2002; 61: 2250–8.[Medline]
14. Lopot F, Nejedly B, Novotna H, Mackova M, Sulkova S. Age-related extracellular to total body water volume ratio (ECV/TBW)—can it be used for "dry weight" determination in dialysis patients? Application of multifrequency bioimpedance measurement. Int J Artif Org 2002; 25: 762–9.[Medline]
15. Pace N, Rathbun EN. The body water and chemically combined nitrogen content in relation to fat content. J Biol Chem 1945; 158: 685–91.[Free Full Text]
16. Wang Z, Deurenberg P, Wang W, Pietrobelli A, Baumgartner RN, Heymsfield SB. Hydration of fat-free body mass: new physiological modeling approach. Am J Physiol 1999; 276: E995–1003.[Medline]
17. St-Onge MP, Wang Z, Horlick M, Wang J, Heymsfield SB. Dual-energy X-ray absorptiometry lean soft tissue hydration: independent contributions of intra- and extracellular water. Am J Physiol Endocrinol Metab 2004; 287: E842–7.[Abstract/Free Full Text]
18. Ljunggren H. Studies on body composition; with special reference to the composition of obesity tissue and non-obesity tissue. Acta Endocrinol 1957; 25: 1–58.
19. Wang J, Pierson RN. Disparate hydration of adipose and lean tissue require a new model for body water distribution in man. J Nutr 1976; 106: 1687–93.[Abstract/Free Full Text]
20. Morse WI, Soeldner JS. The composition of adipose tissue and the non-adipose body of obese and non-obese man. Metab 1963; 12: 99–107.
21. Wong WW, Cochran WJ, Klish WJ, Smith EO, Klein PD. In vivo isotope-fractionation factors and the measurement of deuterium- and oxygen-18-dilution spaces from plasma, urine, saliva, respiratory water vapor, and carbon dioxide. Am J Clin Nutr 1988; 47: 1–6.[Abstract/Free Full Text]
22. Miller M, Cosgriff J, Forbes G. Bromide space determination using anion-exchange chromatography for measurement of bromide. Am J Clin Nutr 1989; 50: 168–71.[Abstract/Free Full Text]
23. Jennings G, Elia M. Automated assay of plasma bromide after a single deproteinization step. Clin Chem 1996; 42: 1210–3.[Abstract/Free Full Text]
24. Fuller NJ, Jebb SA, Laskey MA, Coward WA, Elia M. Four-component model for the assessment of body composition in humans: comparison with alternative methods, and evaluation of the density and hydration of fat-free mass. Clin Sci (Lond) 1992; 82: 687–93.[Medline]
25. Siri WE. Body composition from fluid spaces and density: analysis of methods. In: Brozek J, Henschel A, eds. Techniques for measuring body composition. Washington, DC: National Academy of Sciences NRC, 1961: 223–44.
26. Biaggi RR, Vollman MW, Nies MA, et al. Comparison of air-displacement plethysmography with hydrostatic weighing and bioelectical impedance analysis for the assessment of body composition in healthy adults. Am J Clin Nutr 1999; 69: 898–903.[Abstract/Free Full Text]
27. Waki M, Kral J, Mazariegos M, Wang J, Pierson RN, Heymsfield SB. Relative expansion of extracellular fluid in obese vs. nonobese women. Am J Physiol 1991; 261: E199–203.[Medline]
28. Wang Z, Pierson RN, Heymsfield SB. The five-level model: a new approach to organizing body composition research. Am J Clin Nutr 1992; 56: 19–28.[Abstract/Free Full Text]
29. Fomon SJ, Haschke FH, Ziegler EE, Nelson SE. Body composition of reference children from birth to age 10 years. Am J Clin Nutr 1982; 35: 1169–75.[Free Full Text]
30. Holliday MA. Body composition and energy needs during growth. In: Falkner F, Tanner JM, eds. Human growth. Vol 2. New York, NY: Plenum Press, 1986: 101–17.
31. ICRP. Basic anatomical and physiological data for use in radiological protection: reference values. A report of age- and gender-related differences in the anatomical and physiological characteristics of reference individuals. ICRP Publication 89. Ann ICRP 2002; 32: 5–265.[Medline]
32. Barac-Nieto M, Spurr GB, Lotero H, Maksud MG. Body composition in chronic undernutrition. Am J Clin Nutr 1978; 31: 23–40.[Abstract/Free Full Text]
33. Martin AD, Daniel MZ, Drinkwater DT, Clarys JP. Adipose tissue density, estimated adipose lipid fraction and whole body adiposity in male cadavers. Int J Obes Relat Metab Disord 1994; 18: 79–83.[Medline]
34. Visser M, Gallagher D. Age-related change in body water and hydration in old age. In: Arnaurd MJ, ed. Hydration throughout life. Paris, France: John Libbey Eurotext, 1998: 117–25.
35. Wang Z, Deurenberg P, Wang W, Pietrobelli A, Baumgartner RN, Heymsfield SB. Hydration of fat-free body mass: review and critique of a classic body-composition constant. Am J Clin Nutr 1999; 69: 833–41.[Abstract/Free Full Text]
36. Forbes GB. Human body composition. Growth, aging, nutrition, and activity. New York, NY: Springer, 1987.
37. Horber FF, Thomi F, Casez JP, Fonteille J, Jaeger PH. Impact of hydration status on body composition as measured by dual-energy x-ray absorptiometry in normal volunteers and patients on haemodialysis. Br J Radiol 1992; 65: 895–900.[Abstract]

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