FNDC5 and sarcopenia: Lastly, bivariate associations showed a significant positive correlation between irisin level and waist circumference (r = 0.44, p = 0.05) (Figure 1A) as well as a significant positive correlation between waist to hip ratio (Figure 1B) and conicity index (Figure 1C) (r = 0.51, p = 0.05; and r = 0.45, p = 0.05, respectively), only in the sarcopenia group.