Is glucose still used for glycogen synthesis during fasting?

• A. Yes, to a greater degree
• B. No
• C. Yes but to a lesser degree
• D. Only in the liver

Answer: (C)

During fasting, glycogen synthesis does continue, but at a reduced rate. Insulin levels drop in fasting, which lowers the drive for glycogen formation, yet some glycogen synthase activity remains and the liver can still take up available glucose to store as glycogen when conditions allow. The liver is the main site of glycogen storage, but because insulin is not as high as in the fed state, the extent of glycogenesis is much less than after a meal. Muscle glycogen synthesis is particularly suppressed during fasting due to low insulin and lack of strong stimulatory signals.

So glucose is still used to build glycogen, just to a lesser degree than in the fed state.