measurments and calculations

mass and fluid compartments

Body composition analysis is the clinical assessment of tissue and fluid distribution in the human body. The body is modeled as a series of tissue and fluid compartments.

Fat Mass (FM) is the total amount of stored lipids in the body and consists of the following types of fat:

Subcutaneous Fat is located directly beneath the skin. Subcutaneous fat serves as an energy reserve and as insulation against outside cold.

Visceral Fat is located deeper within the body. Visceral fat serves as an energy reserve and as a cushion between organs.

Fat-Free Mass (FFM), also called Lean Body Mass (LBM), is the total amount of nonfat (lean) parts of the body. It consists of approximately 73% water, 20% protein, 6% mineral, and 1% ash.

Fat-Free Mass is further divided into body cell mass and extracellular mass:

Body Cell Mass (BCM) contains all the metabolically active tissues (living cells) of the body, including muscle cells, organ cells, blood cells, and immune cells. BCM includes the "living" portion of fat cells, but not the stored fat lipids. BCM also includes water inside living cells. This water is called Intracellular Water (ICW). The main electrolyte of intracellular water is potassium.

Extracellular Mass (ECM) contains all the metabolically inactive (non-living) parts of the body, such as bone minerals and blood plasma. ECM includes water contained outside living cells. This water is called Extracellular Water (ECW). The main electrolyte of extracellular water is sodium.

The figure below provides a graphical representation of the relationship of mass and water distribution.

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