Starvation

Abstract

When nutrient intakes do not meet requirements, for whatever reason, stores can provide the gap for a while and the body continues to function normally. Eventually, however, the deficits start to impact physical performance and health. At this point, the body suffers from starvation. The primary concern is protein-energy malnutrition (PEM), but additional deficiencies usually amplify the health threats with starvation. The ability of people to escape the most serious health consequences of starvation for a while depends on the extent and range of nutrients that are lacking and on individual disposition. While considerable amounts of body fat may be lost during starvation, the main danger comes from the breakdown of protein. The obvious general muscle wasting is an ominous feature that points to the parallel loss of functional proteins in heart, liver, kidneys, and other tissues. About 150 g essential amino acids, and a similar quantity of non-essential amino acids is needed daily for the synthesis of proteins in a healthy male of average weight. Much of this can be derived from the breakdown of body proteins. When energy intakes cease to be adequate in a previously well-nourished person and the one-day supply of glycogen is used up, cellular free amino acids, regular protein turnover, and increased mobilization of a small pool of proteins with particularly rapid turnover can cover glucose needs during the first hours of fasting. It is mainly the brain's heavy reliance on a steady supply of glucose that makes gluconeogenesis from amino acids so important.