Lean mass and age are strong determinants of glomerular filtration rate in healthy men

Aims To investigate the association between GFR and body composition in healthy young men with differing body mass. Methods Three age-matched groups were recruited: normal BMI ( n  = 22)  2 , muscular ( n  = 23) with BMI  >  30 kg/m 2 and BIA body fat ≤20%, and obese ( n  = 22) with BMI ≥30 kg/m 2 and BIA body fat  >  30%. Dietary analyses, GFR by clearance of 99m Tc-DTPA, and body composition by dual-energy X-ray absorptiometry (DEXA) were measured in all participants. Results Muscular men had higher GFR (mean 186.4 mL/min; 95% CI 171.7–201.1) than normal BMI and obese groups ( p  = 0.0007). Fat mass protein intake, and smoking status were not associated with GFR; whereas lean mass had the strongest association with GFR. In all subgroups, skeletal muscle mass correlated significantly with GFR ( p  = 0.04). In multi-variate models, variables with the strongest associations with GFR were age ( p  = 0.0009) and lean mass ( p  = 0.0001). Conclusions Age and lean mass were strong determinants of GFR in healthy men of various body compositions. We estimate that GFR decreases by 1 mL/min/year of age and increases 2.3 mL/min/kg of lean mass in healthy men.