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.
In all types of acute disease the whole organism is engaged in the work of eliminating toxins, not in that of assimilating food, hence, it is perfectly natural that the body should rebel against food. Anorexia, foul breath, coated tongue, nausea, vomiting, fetid discharges, the excretion of much mucus, constipation alternating with diarrhea, etc., all indicate that the organs are engaged in the work of vicarious or compensatory elimination, and are not able to digest food. It is not possible to nourish the body by feeding under such circumstances.
"Science and physiology teach," says Dr. Densmore, "that digestion of food can only be performed satisfactorily when there is secretion of the digestive juices; and also that there can be no adequate secretion of the digestive juices, where there is inflammation, or from any cause an absence of appetite. * * * If, as physiologists teach, there can be no effective digestion except from the secretion of digestive juices, and if there is almost no secretion of digestive juices where there is high temperature, we ought to expect that there would be as much emaciation of the fever patient while partaking of food as while fasting; and this is precisely what will be seen to be the result by any physician who will make the experiment. Common sense teaches that if food is taken and not digested, such food does not help nourish the system. If no food at all be taken the processes of life are carried on by consuming the tissues; and if food be taken and not digested the processes of life must be supported by the same consumption of tissues, with the further result that the undigested food must be excreted from the body, which at a glance will be seen to be a strain upon the vital powers, calling for an additional consumption of tissue, and inevitably delaying the restoration of the patient."--How Nature Cures--p.p. 21-22.