BACKGROUND AND AIMS: Modulation of the gut microbiota emerges as a therapeutic possibility to improve health. Our objective was to compare the impact of three months of intervention with diet plus nutritional orientation versus only nutritional orientation on the gut microbiota and metabolic-nutritional profile of outpatients with non-alcoholic steatohepatitis. METHODS: It was a randomized clinical trial with 40 outpatients (49.48 ± 10.3 years), allocated in two groups: DIET group (n=20), who received diet (1.651.34 ± 263.25 kcal; 47% carbohydrates, 28% lipids, 25% proteins, 30 g fibers) and nutritional orientation, and control group (n = 20), which received only nutritional orientation. RESULTS: The DIET group, in relation to baseline, presented a reduction in body weight (p<0.001), BMI (p<0.001), waist circumference (p=0.001), percentage of fat (p=0.002), serum aspartate aminotransferase (p<0.001), alanine aminotransferase (p<0.001), γ-glutamyltransferase (p=0.001), glycemia (p=0.003), homeostasis model assessment of insulin resistance (p=0.017), total cholesterol (p=0.014), and triacylglycerols (p=0.008), whereas the control group did not present changes. After intervention, the small intestinal bacterial overgrowth frequency was 30% in the DIET group and 45% in the control group (p=0.327). In the DIET group, an increase in the density of total microorganisms (3.76 ± 7.17 x 10 8 cells g -1 ; p=0.048) was detected, while in the control group reduced Bacteroidetes (-0.77 ± 2.01 x 10 8 cells g -1 , p=0.044) and Verrucomicrobiales (-0.46 ± 0.75 x 10 8 cells g -1 ; p=0.022) were observed. CONCLUSIONS: The results suggest that exclusively dietary modifications contribute to health promotion in non-alcoholic steatohepatitis and should be the basis of nutritional treatment for this condition.