GCG and diabetes mellitus: After fasting for several days or restricting carbohydrate intake, the glucose reserves in the body are insufficient to produce oxaloacetate in the Krebs cycle for normal fat oxidation and supply of glucose to the central nervous system.63 Thus, most studies believe that the KD leads to decreased blood sugar concentration and a lower insulin-to-glucagon ratio, which is beneficial for glycemic control in individuals with diabetes.20,64 Elevated glucagon levels are associated with hepatic glucose mobilization.