INS and fatty liver disease: Compared to the healthy volunteers, the obese patients before SG had significant hepatic steatosis (p < 0.001), hepatic dysfunction (i.e., ALT, AST, GGT; all p values < 0.001), dyslipidemia (i.e., TC, TG, HDL-c, LDL-c; all p values < 0.01 except TC), and dysglycemia (i.e., fasting glucose, fasting insulin, HOMA-IR; all p values ≤ 0.001) (Table 1 and Additional file 1: Fig. S3).