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.
Despite the fact that the faster maintains normal temperature on a fast, or even has a slight rise in temperature, there is commonly a feeling of chilliness in a moderate temperature in which he ordinarily feels comfortable. This feeling of chilliness may be experienced, even when the bodily temperature is above normal, that is, when there is slight fever. We attribute this feeling of chilliness in individuals of normal or above normal temperature to decreased cutaneous circulation. Let a man strip nude in a cold room and remain there until he feels warm. Then let him walk nude into a warm room. Immediately, shivering results and he will feel cold.
It is well-known that heavy eaters are always complaining of the heat. They may be said to be constantly "feverish." Carrington suggests that the feeling of chilliness may be, in part, due to the absence of this feverishness. He suggests, also, that what is now regarded as normal temperature is a degree too high. The faster, the person on a fruit diet, the moderate eater, comfortable in summer, is likely to feel cold to the touch of the heavy eater.
Carrington records the case of a man whose temperature, by thermometric reading, was regularly, while eating, 2° F. below normal, yet he never felt chilly; but who on the twenty-third day of his fast, his temperature having risen to 97.8° F. (only .6° below normal), felt cold. He gives it as his opinion that the feeling of chilliness in this instance was due, in part at least, to decreased peripheral circulation--an anemia of the skin. But he also thinks that sharpened senses which, as we have seen, are rendered more acute in every instance of fasting, possess a keener perception to changes in body temperature.
We experience a sense of chilliness only when blood has been withdrawn from the skin; when, in other words, there is anemia of the skin, and we may actually be so chilly as to shiver on the hottest summer day. We may feel chilly while the thermometer shows our bodily temperature to be normal or slightly above normal. Geo. S. Keith, M.D., LL.D., records a case of a patient in which, he says: "The great peculiarity in the case was a chilliness coming on when he took anything like a meal."--Fads of An Old Physician, p. 168. This is somewhat a reversal of the chilliness seen in fasting, but it shows that the sensation of chilliness is not due to fasting, per se.
As pointed out before, whatever the explanation of the feeling of chilliness, it has nothing to do with the actual temperature of the body, which may actually be above normal. Susanna W. Dodds says of it: "In this cold paroxysm there is a rise in temperature (which the fever thermometer will detect) sometime before the chilling stage begins."--The Liver and Kidneys, p. 44.