This section is from the book "The Hygienic System: Fasting And Sun Bathing", by Herbert M. Shelton. Also available from Amazon: The Hygienic System Vol III Fasting and Sun Bathing.
"Nothing is remedial," wrote Trall, "except conditions which economize the vital expenditures." The amount of work done by the heart, liver, lungs, kidneys, glands, etc., is largely determined by the amount of food eaten. Why should these organs and the stomach and intestines be given more work to do by eating? Haven't they enough work to perform under the circumstances? Nature demands physiological rest, not physiological over-work. Her call for rest comes in unmistakable terms. Why, then, shall the organs be forced to do extra work by the use of stimulants or by feeding? To stop the use of food for a time affords the most complete rest to the whole vital economy.
Fasting, or physiological rest is the surest way of economizing vital expenditures. Walter pointed out that "the patient often grows stronger through the process of fasting and always better." It should be understood that when food is eaten by the sick man or woman, much of the vital energies must be diverted from the work of purification to that of ridding the body of the unwanted and unusable food. Even in those mild acute diseases, such as the cold, in which but part of the body's energies have been mobilized for the work of disease, and in which considerable digestive power remains, with, perhaps, some desire for food, fasting often means the difference between a mild illness with quick recovery of physiological equilibrium and a severe illness that is long drawn out, or that may end in death.