Objective This study was designed to compare the association between the body mass index (BMI) and symptoms of gastroesophageal reflux disease (GERD) in allegedly normal subjects undergoing regular medical checkups and subjects diagnosed with non-alcoholic fatty liver disease (NAFLD). Additionally, the correlation between the BMI and GERD symptoms was evaluated in subjects with NAFLD. Methods This study included 50 patients with NAFLD and 228 normal subjects evaluated during regular medical checkups. The height, weight, BMI, frequency scale for the symptoms of GERD (FSSG), and serum concentrations of triglycerides and γ-GTP were compared between the two groups. In the NAFLD group, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) concentrations were measured and insulin resistance was calculated using the quantitative insulin sensitivity check index (QUICKI). Results The total FSSG score moderately correlated with the BMI in the NAFLD group (r=0.342, p= 0.015), but correlated negatively in the control group (r=-0.014, p=0.831). The FSSG score in the NAFLD group also negatively correlated with the AST/ALT ratio (r=-0.319) and insulin resistance calculated using the QUICKI score (r=-0.288). The BMI in the NAFLD group moderately correlated with the acid-reflux related score on the FSSG (r=0.389), and both the AST/ALT ratio (r=-0.344) and QUICKI score (r=-0.330) negatively correlated with the dyspepsia score on the FSSG. Conclusion Obesity evaluated by the BMI was a significant risk factor for the exacerbation of GERD symptoms in subjects with NAFLD.