The BCM – Body Composition Monitor is the only device that identifies overhydration as a third compartment on the basis of a unique body composition model.


The clinically relevant output parameters

  • Overhydration (OH)
  • Lean Tissue Mass (LTM)
  • Adipose Tissue Mass (ATM)


are obtained by using two advanced validated physiological models:

In a state of normal hydration with no excess fluid

  • lean tissue (mainly muscle) consists of 70% water whilst the remaining mass is protein and mineral.
  • adipose tissue (the majority of which is lipid) consists of 20% water.
  • excess fluid (overhydration) is almost 100% extracellular water.  


The two compartments ATM and LTM bind a completely different ratio of intracellular and extracellular water (Wang & Pierson 1976, Morse & Soeldner 1963) in

  • lean tissue intracellular water is predominant
  • in adipose tissue extracellular water is predominant

Physiological Models

Physiological Models


  • A volume model describing electrical conductance in a cell suspension enabling the total body water and extracellular water as well as the intracellular water (ICW) to be calculated.¹
  • A body composition model calculating the three relevant body compartments overhydration, lean tissue and adipose tissue from ECW and TBW information.²



¹ Moissl, U et al., Body fluid volume determination via body composition spectroscopy in health and disease. Physiol. Meas 2006; 27: 921-933.

² Chamney, P et al., A whole-body model to distinguish excess fluid from the hydration of major body tissues. Am J Clin Nutr 2007; 85: 80-89

Even in healthy subjects the distribution of lean and adipose tissue mass will lead to significant differences in the ratio of extracellular to intracellular water (E/I). Therefore E/I alone does not provide sufficient information about the hydration status. Overhydration as a third body compartment has to be introduced.


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