Sex-Specific Differences in Lower Body Fat Distribution and Association with Physical Performance among Healthy...

This study aims to examine sex-specific differences in body composition and lower extremity fat distribution and their association with physical performance among healthy older adults. The pilot study comprises 40 subjects (20 men and 20 women) matched by age and body mass index. The participants undergo dual-energy X-ray absorptiometry, magnetic resonance imaging, and proton magnetic resonance spectroscopy (¹H-MRS) to assess body composition and lower extremity fat distribution. ¹H-MRS is used to measure the extramyocellular lipid (EMCL) and intramyocellular lipid (IMCL) contents of the lower leg muscles (soleus and tibialis anterior) at the maximum circumference of the calf after overnight fasting. The tibialis anterior IMCL, as assessed by ¹H-MRS, is negatively associated with the five-times sit-to-stand test scores (r_s = 0.518, p = 0.023) in men, while the soleus IMCL content is negatively associated with the timed up-and-go test scores (r_s = 0.472, p = 0.048) in women. However, the soleus EMCL content is positively associated with the five-times sit-to-stand test scores (r_s = -0.488, p = 0.040) in women, but this association is not statistically significant in men. This study shows an inverse correlation between IMCL content and physical performance in healthy older individuals and lower leg muscle-specific IMCL based on sex differences. Furthermore, our results suggest that greater EMCL content in the soleus and calf subcutaneous fat might affect physical performance positively in women but not men.