Objective: Measurement of the skeletal muscle mass (SMM) is recommended to diagnose sarcopenia. Multifrequency bioelectrical impedance analysis (mBIA) is the preferred method for measuring SMM. However, its accuracy can be low in certain instances, like obesity and edema, and different devices can give different results. We aimed to compare the direct BIA measurement of SMM with the formula-based calculation using tissue resistance.

Materials and Methods: A total of 210 healthy volunteers aged 18-40 years were included in the study. Participants' SMM1 were measured directly using mBIA, and SMM2 was calculated using the Janssen formula with tissue resistance. SMMI (kg/m2) was calculated with SMM divided by height. Two standard deviations (SD) below the mean values of both measurements were accepted as cut-off points for low muscle mass.

Results: A total of 114 females (54.3%) and 96 males (45.7%) were included in the study (mean age: 26.6±5.5 years, mean BMI 23.7±4.0 kg/m2). Mean SMMI1 and SMMI2 for males were 19.43±1.67 and 9.73±0.75 kg/m2, which were 16.09±1.68 and 7.28±0.67 kg/m2 for females. The cut-off points for low muscle mass according to SMMI1 and SMMI2 measurements were 16.19 and 8.23 kg/m2 in males and 12.73 and 5.94 kg/m2 in females, respectively.

Conclusion: The present study showed that Janssen’s formula-based calculation of the SMM using tissue resistance of BIA is significantly lower than the SMM measured by BIA itself. BIA results obtained by direct measurement lead to higher cut-off values, so using formula-based SMM in clinical practice may prevent the overestimation of muscle mass and the prevalence of sarcopenia.