GLUCONEOGENESIS IS THE MAIN SOURCE OF GLUCOSE DURING FASTING.

Previous research has suggested that during the first hours of fasting, glycogenolysis contributes more to the maintenance of blood sugar than gluconeogenesis. A new study, using what is probably more accurate technology, comes to a different conclusion.

Seven healthy young adults were loaded with a standard high-carbohydrate diet for 3 days, after which they fasted for 68 hours. The rate of total glucose production was measured with tritiated glucose. The production of glucose by glycogenolysis was evaluated by measuring the progressive depletion of glycogen from liver stores, using magnetic resonance imaging. Glucose production by gluconeogenesis then was estimated by subtracting glucose produced by glycogenolysis from total glucose produc…