Materials and methods: This double blinded clinical trial study was performed in 2012 among patients referring to gastrointestinal clinics in the city of Ilam. 105 non-alcoholic fatty liver patients were selected and participated in this study. Patients were randomly divided into two groups of metformin and pioglitazone. Using double blinded clinical trial, one group was treated by pioglitazone (30 mg daily) and the other by metformin (500 mg daily) both for 3 months. Then using sonography, the severity of fatty liver was compared in the two groups.

Results: Multivariable logistic regression showed that there was no significant difference between the effect of pioglitazone and metformin on the treatment of fatty liver (p=0.92). There was a significant difference between severity of fatty liver and BMI before treatment (p<0.004) but it was not confirmed after the treatment. There was also a significant difference between the severity of fatty liver and gender before treatment (p<0.003) but it was not confirmed after treatment. There was a negative significant relationship between age and the treatment effect of metformin but not in the pioglitazone group.

Conclusions: Both pioglitazone and metformin had a notable effect on the treatment of fatty liver solely while there was no significant difference between their effectiveness. The effectiveness of metformin was higher among males compared to that of pioglitazone.