During short periods between meals (up to 8 to 12 hours), what process is the liver primarily using to maintain glucose levels?

The process that the liver primarily utilizes to maintain glucose levels during short periods between meals (up to 8 to 12 hours) is glycogenolysis. During fasting or periods of low glucose availability, such as between meals, the liver breaks down glycogen, which is a stored form of glucose. This breakdown releases glucose into the bloodstream, helping to stabilize blood glucose levels and provide energy to the body, particularly to tissues that rely heavily on glucose, like the brain.

Glycogenolysis is a rapid process compared to gluconeogenesis, where glucose is synthesized from non-carbohydrate sources (like amino acids or glycerol), which takes longer and is typically used during more prolonged fasting. The focus during the shorter fasting state is to quickly mobilize stored glycogen to ensure that blood glucose levels remain within a normal range, as the body prefers to utilize pre-existing stores for immediate energy needs.

Understanding this distinction helps emphasize the liver's role in glucose homeostasis immediately after food intake has ceased.