fat_free_mass: Fat-Free Mass (Janmahasatian Equation)

In cliot: Clinical Indices and Outcomes Tools

Fat-Free Mass (Janmahasatian Equation)

Description

Calculates the Fat-Free Mass (FFM) of a patient using the Janmahasatian equation. This metric is often used for pharmacokinetic dosing of drugs with narrow therapeutic indices (e.g., digoxin, aminoglycosides) in obese patients, as it provides a more accurate estimate of metabolically active tissue than total body weight or ideal body weight.

Usage

fat_free_mass(weight_kg, height_cm, sex)

Arguments

weight_kg	Numeric. Patient actual body weight in kilograms.
height_cm	Numeric. Patient height in centimeters.
sex	String. Patient sex ("Male" or "Female").

Value

A list containing:

Fat_Free_Mass_kg	The calculated Fat-Free Mass in kg.
BMI	The calculated Body Mass Index used in the equation.

References

Janmahasatian S, Duffull SB, Ash S, Ward LC, Byrne NM, Green B. Quantification of lean bodyweight. Clin Pharmacokinet. 2005;44(10):1051-1065. doi:10.2165/00003088-200544100-00004

Examples

# Example 1: Male
# 80kg, 180cm
fat_free_mass(80, 180, "male")

# Example 2: Female
# 70kg, 165cm
fat_free_mass(70, 165, "female")

cliot documentation built on Dec. 1, 2025, 1:06 a.m.