-Guisinger
-Proposes that the typical AN symptoms of food restriction, hyperactivity and denial of starvation, reflect the operation of adaptive mechanisms that once caused migration in response to local famine conditions. Normally, when a person begins to lose weight, physiology mechanisms conserve energy and increase desire for food. These adaptions facilitate survival in hard times. However, among ancestral nomadic foragers, when extreme weight loss was due to a severe depletion of local food resources, this adaption must be turned off so that individuals can increase their chances of survival by migrating to a more favourable environment. Food restriction is a common feature of many species when feeding competes with other activities such as migration or breeding. During the Middle Ages, the phenomenon of 'holy anorexia' was widespread among pious women. The hyperactivity typically found in anorexics may be a form of 'migratory restlessness' as many species increase activity in times of food shortage and prior to migration. In the EEA those starving foragers who deceived themselves about their physical condition would have been more confident about moving on to a more favourable (in terms of food availability) environment, and so would have been more likely to survive. Therefore, for modern-day individuals, among those who are genetically vulnerable to AN, losing too much weight may trigger these ancestral mechanisms.