The camel’s hump is filled largely with fat, accumulated at times when food and water are available. This fat is digested to meet the energy needs of the animal. Camels can go for a week or more without water and for 10 days without food. During such periods the accumulated fat is used up. The hydrogen released as a by-product by the breakdown of fat combines with the oxygen the camel breathes in to produce water. By utilizing this metabolic water the camel can keep going for many days. In this process, it may lose up to 100 kg of body weight. But as soon as it arrives at an oasis, it is capable of rapidly drinking some 120 litres of water.