The aim of the study was to compare the effects of a lacto-ovo-vegetarian diet (LOV-D) vs. a standard weight-loss diet (SWL-D) on obese/overweight adults with NAFLD. Present randomised clinical trial recruited 75 overweight/obese adults with NAFLD, who were randomly assigned into LOV-D and SWL-D groups for 3 months. The LOV-D was designed based on eliminating meat, poultry, and fish; while including dairy products and eggs. The SWL-D was planned according to the standard food pyramid, which was free in all sources of food. Adherence to LOV-D significantly outperformed SWL-D in reducing levels of alanine aminotransferase (ALT), body weight, waist circumference, BMI, fasting blood sugar, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), triacylglycerol (TG), cholesterol, low-density lipoprotein cholesterol (LDL-C), and systolic blood pressure (SBP). Furthermore, ultrasonography revealed a higher alleviation in NAFLD grade among LOV-D, compared with SWL-D. This study suggests that adherence to LOV-D for 3 months has beneficial effects on NAFLD improvement, anthropometric measures, glycaemic-related markers, and lipid profiles.