Objective To investigate the association between intestinal permeability and severity of nonalcoholic fatty liver disease (NAFLD), and the value of intestinal permeability in predicting the efficacy of metabolic therapy for NAFLD. Methods Disease severity was compared between patients with normal and elevated intestinal permeability; correlations between D-lactate and different NAFLD parameters were analyzed; and the effects of metabolic therapy on NAFLD patients with normal and elevated intestinal permeability were evaluated. Results A total of 190 patients with NAFLD were enrolled. NAFLD patients with elevated intestinal permeability had significantly higher levels of liver test parameters, liver ultrasonographic fat attenuation parameter, triglyceride, homeostasis model assessment of insulin resistance value and diamine oxidase (all P˂0.05) than NAFLD patients with normal intestinal permeability. Further, serum D-lactate levels were positively correlated with alanine transaminase, aspartate transaminase, gamma-glutamyl transpeptidase, total bilirubin, indirect bilirubin, fat attenuation parameter, triglyceride, and diamine oxidase (all P˂0.05). Moreover, NAFLD patients with elevated intestinal permeability showed less improvement in TG levels (P=0.014) after metabolic therapy. Conclusion Intestinal permeability correlates with the disease severity in patients with NAFLD. Moreover, intestinal permeability may have value for predicting the efficacy of metabolic therapy for NAFLD patients.