The Cardiovascular
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Fat free mass (FFM)

Predicts fat-free (lean) body mass from weight, height and sex.

Fat free mass (FFM)
Sex
Weight
Height
Complete the fields above to see the result.

When to use

  • Estimating lean/fat-free body mass to scale drug dosing (e.g. induction agents) in patients across a wide weight range, including obesity.

Formula

Men: FFM = (9270 x weight) / (6680 + 216 x BMI). Women: FFM = (9270 x weight) / (8780 + 244 x BMI). Weight in kg, BMI in kg/m2.

Pearls and pitfalls

  • Derived from a semi-mechanistic model referenced against dual-energy x-ray absorptiometry (DXA), not simple anthropometric regression.
  • Performs more consistently than older lean-body-weight equations at extremes of body size.

References

  1. Janmahasatian S, et al. Clin Pharmacokinet. 2005;44(10):1051-1065.