Muscle mass adjustment for body size: is using a ratio doing the job? A cross-sectional study in two samples of older adults.

PURPOSE: The aim of this cross-sectional study was to investigate the prevalence of low muscle mass using different ratios, across categories of BMI in older adults.

METHODS

Muscle mass estimates obtained by DXA, CT, and BIA from two samples of older adults were used (the Health, Aging, and Body composition study, USA and the MUSCLE study, Japan). For each muscle mass estimate, three ratios were calculated: muscle mass divided by body height squared, muscle mass divided by body weight, and muscle mass divided by body mass index. The prevalence of low muscle mass (ratio < 20th percentile of the sample) was determined across BMI categories.

RESULTS

For all three ratios, the prevalence of low muscle mass was dependent on BMI. These findings were consistent for the different body composition methods, men and women, and for the two data samples.

CONCLUSION

Regardless of the muscle mass-body size ratio being used, cut-off values for low muscle mass need to be BMI-specific.