Columbia University

Principle of BIA (Cylindrical model)
Suppose the human body consists of fat free
mass with a resistivity of ρ and fat with ∽.
Given the cross-sectional area is S, the
length L, and the volume V.
Resistance R = ρ L/S. Multiply the right
side by L/L to obtain:
R = ρL 2 /SL = ρL 2 /V
Hence,
V = ρL 2 /R
It implies the water percentage in the body.
Because
density = weight/V,
it can be expressed by:
density = weight × R/ρL 2
Current
脂 Fat 肪 組 織
Fat 除 free 脂 肪 mass 組 織
L