Both the fat free body mass and body fat mass can be normalized for height, analogous to total body mass in the body mass index. This can provide more useful information for evaluation of a patient with over- or undernutrition. The authors are from the Columbia University in New York and the University of Illinois in Urbana.


Problem with non-normalized fat free and body fat masses: A tall person with protein energy malnutrition may have values comparable to a shorter person who is well-nourished.


Fat free or lean body mass is estimated or measured using a method such as bioimpedance, body density, or skinfold measures.


body fat mass in kilograms =

= (total body mass in kilograms) – (fat free mass in kilograms)


fat free mass index (FFMI) =

= (fat free body mass in kilograms) / ((body height in meters)^2)


body fat mass index (BFMI) =

= (body fat mass in kilograms) / ((body height in meters)^2)


Because (body mass) = (fat free mass) + (body fat mass)


body mass index (BMI) =




• A FFMI or BFMI below the 5th percentile for a reference population was associated with protein-energy malnutrition.


Minnesota Study of Keys et al (1950)

50th percentile

5th percentile


20 kg per square meter

17 kg per square meter


4.4 kg per square meter

2.45 kg per square meter

from Figures 2 and 3, page 955, VanItallie (1990)


It might be interesting to see if the ratio of the (body fat mass) / (fat free body mass) has any use in obesity research.


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