An association between food intake and life is both evident and banal. Simply, food is essential. Any level of human activity, starting from cellular metabolism (e.g., synthesis of biomolecules) through tissue physiology (e.g., muscle contraction) to organism physiology (e.g., physical labor or sports), requires energy expenditure. The main purpose of nutrition is to provide energy for current and future consumption. Otherwise, food is necessary for body growth, maintenance, and tissue repair. Such an intuitive understanding of nutrition, with no precise knowledge concerning the biology of feeding, was satisfactory for centuries. Acquiring the amount of food sufficient to survive was the main and often the only priority for an individual as well as for a group or population. Regardless of the way the food was gained, be it hunting, agriculture, war, or robbery, a shortage or abundance of food was an indication of poverty or prosperity, of a poor or fortunate life. Populations of early food-gatherers, hunters, farmers, and even well-trained eighteenth-century soldiers (“an army has to feed itself”) repeatedly faced the same problem: a shortage of food during the period preceding the next hunt or harvest. And, given the threat of famine versus that of any negative health effects connected with feeding, the former would always prevail.