Starvation is the total deprivation of food. Here is what happens during starvation: Initially, the body utilizes its glycogen reserves. Then it moves on to its fat reserves — the first ones are those around the heart and kidneys. Finally, the body relies on the reserves found in the bone marrow. Early in a total fast, the body metabolizes protein at a rapid rate. The amino acids are converted to glucose, because the brain prefers glucose. These proteins come from the skeletal muscles, blood plasma, and other sources in a process that produces a quantity of nitrogen-containing products, which need to be excreted. Excretion requires large quantities of water, and the resulting loss of water may lead to death by dehydration. If the starvation continues, the brain chemistry adjusts to accept fatty acid metabolites, which uses the last of the fat reserves. Finally, the body resorts to structural proteins, systems begin to fail rapidly, and death follows quickly.