Glycogen and glucose remain plentiful. In this postprandial or "fed" state, the liver takes in more glucose from the blood than it releases. After a meal has been digested and glucose levels begin to fall, insulin secretion is reduced, and glycogen synthesis stops. When it is needed for energy, glycogen is broken down and converted again to glucose. Glycogen phosphorylase is the primary enzyme of glycogen breakdown. For the next 8–12 hours, glucose derived from liver glycogen is the primary source of blood glucose used by the rest of the body for fuel. Glucagon, another hormone produced by the pancreas, in
Starvation their normal body weight. Once the loss reaches 40% death is almost inevitable. Under normal metabolic conditions, the human body relies on free blood glucose as its primary energy source. The level of blood sugar is tightly regulated; as blood glucose is consumed, the pancreas releases glucagon, a hormone that stimulates the liver to convert stored glycogen into glucose. The glycogen stores are ordinarily replenished after every meal, but if the store is depleted before it can be replenished, the body enters hypoglycemia, and begins the starvation response. After the exhaustion of the glycogen reserve, and for the next 2–3