Objective Recently, lipidemia and glucose tolerance were reported to be improved by oral administration of nitrate in eNOS (endothelial NO synthase) deficient mice. On the other hand, about 25% of dietary nitrate is reduced into nitrite by bacterial conversion in oral cavity. Therefore we hypothesized that nitrite should ameliorate metabolic disorders. In this study, we studied metabolic consequences of semi-chronic oral administration of nitrite in high fat diet (HFD)-fed rats to clarify the metabolic benefits of nitrite. Methods Male Wistar rats at the age of seven weeks were fed normal diet or 60% HFD for one to two weeks with or without sodium nitrite given in drinking water (0.1%). Blood glucose and plasma lipid indexes were determined. Glucose tolerance was evaluated by oral glucose tolerance test (OGTT). AMPK activities were evaluated by an index of phosphorylation of AMPKα subunit using western blotting in Fao rat hepatoma cells. Results The administration of nitrite did not affect either body weight or food intake during the study. Blood glucose levels during OGTT were ameliorated by dietary nitrite. Furthermore, blood triglyceride was decreased by ~50% in nitrite-treated rats. Nitrite stimulation increased phosphorylation levels of AMPK in Fao cells. Conclusion We found that dietary nitrite improves glucose tolerance caused by HFD. Furthermore, dietary nitrite has striking lipid lowering effects. These metabolic benefits of nitrite are suggested to be mediated at least partly by AMPK activation in such metabolic tissues as liver. In conclusion, we suggest that nitrite should be one of the effective materials which improve disorders of diet-induced obesity.