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.
There is much fear on the part of many, that fasting may result in tuberculosis. They have the idea that to get thin is to lay oneself liable to this "disease." This fear is unfounded and is based on a false view. The thinness in tuberculosis is not the cause of the trouble but the result of its cause. Loss of weight seems to be essential to recovery from acute "disease," and nature makes certain that the acute sufferer loses weight no matter how much food is taken. Indeed, a typhoid fever patient will lose weight and strength more rapidly if fed in the usual manner, than if fasting. Due to the fact that the fasting patient recovers more quickly, and even better, during the most prolonged fast, than when fed the accustomed amounts of "good nourishing food," such a patient will lose less weight if he fasts than if he is fed.
The loss of weight during a fast does not represent a loss of vital tissue, but of surplus nutriment, waste, fat, etc. It is just so many pounds of "disease" that one loses. The muscles, for example, decrease in size. But this is due to a decrease in the amount of fat in them, and to a decrease in the size of their cells. There is no actual lessening of the number of muscle cells during the ordinary fast.
Tuberculosis quite often develops in the plethoric and "well-fed." Professor Morgulis rightly declares, "as a social phenomenon, malnutrition is not simply a matter of either insufficient or improper nourishment: It is the sinister combination of blighting influences of poverty--overcrowding, under-clothing, unhealthy and unhygienic environment. Here is the fertile soil on which tuberculosis reaps its ghastly harvest."
The weight lost during a fast is rapidly regained, if it is desirable to do so. There is not the slightest danger from loss of weight.