Abstention from, or deprivation of, food and drink. It may result from a genuine desire to lose weight – in an attempt to improve health and/or appearance – or from a MENTAL ILLNESS such as DEPRESSION, or from an EATING DISORDER. Certain religious customs and practices may demand periods of fasting.

Without food and drink the body becomes thinner and lighter as it draws upon its stored energy reserves, initially mainly fat. Body temperature gradually falls, and muscle is progressively broken down as the body struggles to maintain its vital functions. Dehydration, leading to collapse of the blood circulatory system, eventually follows unless a basic amount of water is taken.