Gluconeogenesis
Gluconeogenesis (GNG) is a chemical process in living bodies.  In gluconeogenesis, the body turns fats and proteins (glucogenic amino acids) into sugars called glucose. In most animals with spines, gluconeogenesis happens in the liver, but some animals have gluconeogenesis in the kidneys. gluconeogenesis usually happens when the organism has not eaten many starches or sugars or  eaten nothing at all for a long time.  Not eating and not eating starch can cause ketosis, which is when some cells cannot use ketones for fuel.