49
VIII. ABOUT RESULTS
The Fat-free Mass Index (FFMI), Fat Mass Index (FMI), and Skeletal Muscle Index (SMI) is an
equivalent concept to BMI, but using fat-free mass, fat mass, and skeletal muscle mass rather
than total weight mass. This makes it possible to determine body type, and the source of weight.
Fat-free Mass is the weight of the body after fat mass has been subtracted, and includes Skeletal
Muscle Mass. An increase in SMM (muscle gains) will cause an increase in FFM. However, the
opposite isn't necessarily true - an increase in FFM is not necessarily due to muscle. One major
reason for this is because a significant portion of FFM is water.
Combining the Fat-free Mass Index, Fat Mass Index, and Skeletal Muscle Index makes it easier
for professionals to evaluate changes in the subject's composition.
Cut-off points for risk of sarcopenia:
Various literature is available regarding the definition of cut-off points, but no universal standards
exist. Cut-off points can vary based on age and ethnicity. As a guideline though, the following
cut-off points can be considered for reference as indicators of lower than normal fat-free mass
and skeletal muscle mass:
FFMI: <16.7kg/m
2
(men) and <14.6kg/m
2
(women)
31
SMI: < 8.5kg/m
2
(men) and < 5.75kg/m
2
(women)
32
31. Schutz Y, Kyle UU, Pichard C. Fat-free mass index and fat mass index percentiles in caucasians aged 18-98 y. Int
J Obes Relat Metab Disord J Int Assoc Study Obes. 2002;26(7):953–960
32. Baumgartner R, Koehler K, Gallagher D, et al. Epidemiology of sarcopenia among the elderly in New Mexico, Am J
Epidemiol, 1998, vol.147 (p.755-63)
Impedance
The MA801 measures the impedance for the right arm (RA), left arm (LA), trunk (TR), right leg
(RL), and left leg (LL) using 5 different frequencies.
Impedance
RA LA TR
RL
LL
5kHz
20kHz
50kHz
100kHz
250kHz
361.9 355.6 25.2 273.0 272.6
339.4 331.8 22.1 253.3 252.9
326.3 318.5 20.5 244.7 243.8
330.4 322.2 18.1 243.7 243.1
305.8 329.6 12.2 229.2 227.4