FNDC5 and metabolic dysfunction-associated steatotic liver disease: On the other hand, in the NAFLD group including both the mild fatty liver group and the moderate-to-severe fatty liver group, the serum irisin level tended to be higher in the non-obese group than the obese group; however, the difference did not reach statistical significance (73.1±48.5 vs. 62.9±21.2, p = 0.365 and 59.7±18.0 vs. 54.6±23.3, p = 0.505) (Figure 2).