Insulin is required for carbohydrate, fat, and protein to be metabolized. With respect to carbohydrate from a clinical standpoint, the major determinate of the glycemic response is the total amount of carbohydrate ingested rather than the source of the carbohydrate. This fact is the basic principle of carbohydrate counting for meal planning. Fat has little, if any, effect on blood glucose levels, although a high fat intake does appear to contribute to insulin resistance. Protein has a minimal effect on blood glucose levels with adequate insulin. However, with insulin deficiency, gluconeogenesis proceeds rapidly and contributes to an elevated blood glucose level. With adequate insulin, the blood glucose response in persons with diabetes would be expected to be similar to the blood glucose response in persons without diabetes. The reason why protein does not increase blood glucose levels is unclear. Several possibilities might explain the response: a slow conversion of protein to glucose, less protein being converted to glucose and released than previously thought, glucose from protein being incorporated into hepatic glycogen stores but not increasing the rate of hepatic glucose release, or because the process of gluconeogenesis from protein occurs over a period of hours and glucose can be disposed of if presented for utilization slowly and evenly over a long time period.