Glycogen grams of glucose are present in the blood of humans at all times; in fasted individuals, blood glucose is maintained constant at this level at the expense of glycogen stores in the liver and skeletal muscle. Glycogen stores in skeletal muscle serve as a form of energy storage for the muscle itself; however, the breakdown of muscle glycogen impedes muscle glucose uptake, thereby increasing the amount of blood glucose available for use in other tissues. Liver glycogen stores serve as a store of glucose for use throughout the body, particularly the central nervous system. The human brain consumes approximately 60%
Cyclic ketogenic diet goals of a refeed are threefold: The refueled glycogen stores can then be used for higher-intensity training to maintain or increase endurance / muscle mass after the refeed. Normally this sort of training would be relatively impossible on a pure ketogenic diet, as glycogen stores in the body are almost constantly depleted. The refeed process can lead to gaining fat if more carbs are consumed than needed to replenish glycogen stores. The timing, duration, and macronutrient composition of a refeed are crucial to the overall success of the diet. According to a published article in the "British Journal of Nutriton"