Britannica
Sources used in this answer
How does the liver help maintain blood glucose during fasting?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
human body
Vintage anatomy charts of the human body showing the skeletal and muscle systems.
During fasting, the liver plays a critical role in maintaining blood glucose levels through two primary metabolic processes, both of which are stimulated by an increase in the hormone glucagon and a decrease in insulin secretion:123
- Glycogenolysis: As blood glucose levels fall, the liver breaks down stored glycogen into glucose, which is then released into the bloodstream to restore normal levels.123
- Gluconeogenesis: Once liver glycogen stores are depleted, the liver produces new glucose from non-carbohydrate sources, specifically amino acids and [glycerol].12
These mechanisms ensure that the body, particularly the brain, receives a steady supply of energy when dietary intake is absent. As fasting continues, the liver also converts fatty acids into ketone bodies, providing an alternative fuel source that reduces the body's reliance on glucose production and helps spare muscle tissue.1