Capital punishment
Historically, starvation has been used as a death sentence. From the beginning of civilization to the Middle Ages, people were immured, and died for want of food. In ancient Greco-Roman societies, starvation was sometimes used to dispose of guilty upper-class citizens, especially erring female members of patrician families. In the year 31, Livilla, the niece and daughter-in-law of Tiberius, was discreetly starved to death by her mother for her adulterous relationship with Sejanus and for her complicity in the murder of her own husband, Drusus the Younger. Another daughter-in-law of Tiberius, named Agrippina the Elder (a granddaughter of Augustus and the mother of Caligula), also died of starvation, in 33 AD; however, it is unclear if her starvation was self-inflicted. A son and daughter of Agrippina were also executed by starvation for political reasons; Drusus Caesar, her second son, was put in prison in 33 AD, and starved to death by orders of Tiberius (he managed to stay alive for nine days by chewing the stuffing of his bed); Agrippinas youngest daughter, Julia Livilla, was exiled on an island in 41 by her uncle, Emperor Claudius, and her death by starvation was arranged by the empress Messalina. It is also possible that Vestal Virgins were starved when found guilty of breaking their vows of celibacy. Ugolino della Gherardesca, his sons, and other members of his family were immured in the Muda, a tower of Pisa, and starved to death in the thirteenth century. Dante, his contemporary, wrote about Gherardesca in his masterpiece The Divine Comedy.
Thus, when fatty acids are being broken down for energy, all of the remaining glucose is made available for use by the brain.After two or three days of fasting, the liver begins to synthesize ketone bodies from precursors obtained from fatty acid breakdown. The brain uses these ketone bodies as fuel, thus cutting its requirement for glucose. After fasting for three days, the brain gets 30% of its energy from ketone bodies. After four days, this may increase to 70% or more. Thus, the production of ketone bodies cuts the brains glucose requirement from 80 g per day to 30 g per day, about 35% of normal, with 65% derived from ketone bodies. But of the brains remaining 30 g requirement, 20 g per day can be produced by the liver from glycerol (itself a product of fat breakdown). This still leaves a deficit of about 10 g of glucose per day that must be supplied from another source; this other source will be the bodys own proteins. After exhaustion of fat stores, the cells in the body begin to break down protein. This releases alanine and lactate produced from pyruvate, which can be converted into glucose by the liver. Since much of human muscle mass is protein, this phenomenon is responsible for the wasting away of muscle mass seen in starvation. However, the body is able to choose which cells will break down protein and which will not.