It is known that the excess fat stored within muscle tissues in two forms; i.e. intramyocellular (IMCL) and extramyocellular lipids (EMCL)(1). Some studies reported that both IMCL and EMCL contents increase with total body fat mass and ageing (2). In contrast, it is paradoxically reported that high IMCL content is observed in endurance athletes (3). The precise physiological role of IMCL and EMCL remains uncertain. PURPOSE: The aim of this study was to confirm the interrelationship between age, whole body adiposity, and muscle size on the concentration of IMCL and EMCL. METHODS: Two hundred sixty-four male subjects participated (age range 17-82 years) in the study. Body mass index ranged from 16.4 to 33.3 kg/m2 (means ± SD, 23.1 ± 2.8 kg/m2). The present study was approved by the research ethics committee involving living human participants in Ritsumeikan University. Written informed consent was obtained from all subjects. For separate quantification of IMCL and EMCL, noninvasive localized proton magnetic resonance spectroscopy (1H-MRS) measurement of the right vastus lateralis was performed on a 1.5T MR system (Signa HDxt, GE Medical Systems). Multi-slice T1-weighted spin-echo images were acquired to guide the positioning of the volume of interest, and used for measuring the muscle CSA. Thereafter, the single voxel MRS measurements were performed using a PRESS sequence (TR/TE 2000/35 ms, 20 × 20 × 20 mm3, 32 acqs). The estimation of the muscle lipid concentration was accomplished by the LCModel software with customized calculation reported by Weis et al. (2009) (4). Whole body fat mass (%fat) was measured by dual-energy X-ray absorptiometry (Lunar Prodigy, GE Medical Systems). The measurement was performed after an overnight fast. Simple linear regression was applied to examine the relationships between age, %fat, muscle size and each of absolute concentration of IMCL and EMCL. Pearson’s regression coefficient was calculated. Multiple linear regression models with age, %fat and muscle CSA as independent variables were used to calculate the dependent variables. RESULTS: The concentrations of IMCL and EMCL were 9.5 ± 5.2 mmol/kg and 21.4 ± 20.7 mmol/kg (means ±SD), respectively. The EMCL level positively correlated with age (r=0.58, p<0.05) and %fat (r=0.51, p<0.05), and negatively correlated with muscle CSA (r=-0.52, p<0.05). The partial coefficient of correlation between %fat and EMCL was still significant when adjusted for age and muscle CSA (r=0.34, p<0.05). There was no significant correlation between IMCL and either age, %fat and muscle CSA. CONCLUSION: These results indicate that the amount of EMCL in the vastus latelaris is associated with the whole body adiposity, while IMCL is independent of whole body adiposity.