BACKGROUND AND PURPOSE Fibroblast growth factor 21 (FGF21) has emerged as a therapeutic strategy for treating type 2 diabetes mellitus due to its antidiabetic effects, and this has led to the development of FGF21 longacting analogs. These compounds have some limitations, including requiring subcutaneous injection and their prolonged pharmacodynamic effect compared with native FGF21, which might be responsible for their reported side effects. EXPERIMENTAL APPROACH We have previously demonstrated that intraperitoneal administration of heme-regulated eukaryotic translation initiation factor 2α (eIF2α) kinase (HRI) activators increases hepatic and circulating levels of FGF21. In this study, we examined the effects of oral administration of a new HRI activator, EPB-53, on high-fat diet (HFD)-induced glucose intolerance, hepatic steatosis, and hypertriglyceridemia, compared with metformin. KEY RESULTS Administration of EPB-53 administration for the last two weeks, to mice fed a HFD for 10 weeks, reduced body weight gain, improved glucose intolerance, and prevented hepatic steatosis and hypertriglyceridemia; whereas metformin only ameliorated glucose intolerance. Moreover, EPB- 53, similarly to the reported effects of FGF21, reduced lipogenesis in cultured human hepatocytes and in the liver of mice fed a HFD. Administration of EPB-53 to Fgf21-knockout mice had no effects, demonstrating that its efficacy is dependent on this hormone. CONCLUSIONS AND IMPLICATIONS Overall, the findings of this study demonstrate that oral administration of HRI activators is a promising strategy for the treatment of type 2 diabetes mellitus and non-alcoholic fatty liver disease by increasing FGF21.