This system review summarized the data from 37 randomized controlled trials, comparing synbiotics, probiotics, prebiotics, fecal transplantation, and antibiotics on liver enzymes (ALT, AST), glycolipid metabolism (TG, TC, LDL-C, HDL-C, HOMA-IR), and non-invasive steatosis and fibrosis in the liver (CAP, LSM) in 1921 patients with NAFLD. The gene discussed is GPT; the disease is fibrosis.