Paving the way for applying GLIM criteria in clinical practice and research: how to define mild to moderate and severe reduced muscle mass

Among approaches to adjust skeletal muscle mass (SMM) for body size, adjustment for body mass index (BMI) correlated better with functional measures. To enhance applicability of GLIM criteria, we report grade 1 and grade 2 reduced muscle mass cut-offs for SMM adjusted by BMI.301 young, healthy adults involving students, patient relatives and staff working in the university hospital were included. SMM was estimated by bio-impedance analysis (BIA). SMM index (BMI) [SMMI(BMI)] was calculated as SMM/BMI. Grade 1 low muscle mass (LMM) was defined as "mean young SMMI(BMI)-one standard deviation" and grade 2 LMM as "mean young SMMI(BMI)-two standard deviations".Mean age was 26.5 ± 4.6 (62.1% male). Grade 1 vs grade 2 LMM thresholds were 1.189 and 0.954 kg/BMI vs 1.049 and 0.823 kg/BMI in males and females, respectively.This is the first report identifying stage 1 and stage 2 LMM thresholds for SMMI adjusted by BMI. Studies are needed to evaluate their predictive validity.