Reduced glutathione (GSH) levels in freeze-clamped livers of rats and mice in which hyperphagia is induced by cafeteria diet are 45% lower than in controls. Freshly isolated hepatocytes from mice fed cafeteria diet show a 45% decrease in GSH concentration and a 54% decrease in oxidized glutathione (GSSG) concentration when compared with controls. The rate of GSH synthesis in isolated hepatocytes from control mice is significantly higher than in those from mice fed cafeteria diet. Oral GSH is effective to prevent the decrease in hepatic GSH levels found in cafeteria fed mice.