"WHY do we eat?" This question, presented to a group of educated people, is likely to bring forth the answer, "We eat to compensate for body waste, or to supply the body with fuel for its labors." Although the body is in fact losing weight continuously and drawing continuously on its store of energy, and although the body must periodically be supplied with fresh material and energy in order to keep a more or less even balance between the income and the outgo, this maintenance of weight and strength is not the motive for taking food.
Primitive man, and the lower animals, may be regarded as quite unacquainted with notions of the equilibrium of matter and energy in the body, and yet they take food and have an efficient existence, in spite of this ignorance. In nature, generally, important processes, such as the preservation of the individual and the continuance of the race, are not left to be determined by intellectual considerations, but are provided for in automatic devices. Natural desires and impulses arise in consciousness, driving us to action; and only by analysis do we learn their origin or divine their significance. Thus our primary reasons for eating are to be found, not in convictions about metabolism, but in the experiences of appetite and hunger.
Appetite and Hunger
The sensations of appetite and hunger are so complex and so intimately interrelated that any discussion is sure to go astray unless at the start there is clear understanding of the meanings of the terms. The view has been propounded that appetite is the first degree of hunger, the mild and pleasant stage, agreeable in character; and that hunger itself is a more advanced condition, disagreeable and even painful—the unpleasant result of not satisfying the appetite. On this
- Presented to the Harvey Society, New York City, December 16, 1911. The results here stated were published in the American Journal of Physiology, 1912, XXIX., pp. 41-454.
- Bardier, Richet's "Dictionnaire de Physiologie," article "Faim," 1904, VI., p. 1. See, also, Howell, "Text-book of Physiology," fourth edition, Philadelphia and London, 1911, p. 285.