Q: Could shift in delayed circadian rhythm of glucose metabolism be responsible for higher fasting blood sugar than post prandial?

A:To the best of my knowledge shift in circadian rhythm does not cause higher fasting glucose than PP. This suggests a quicker insulin release from pancreas. After food intake insulin release from pancreas is in two phases. First sharp rise followed by a slow release. Apart from this there is basal insulin secretion from pancreas which keeps blood glucose in normal range. This basal release is also controls hepatic glucose output thus controlling fasting blood glucose levels.