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.
The brain and nervous system are supported and lose little or no weight during a fast, while the less important tissues are sacrificed to feed them. They maintain their power and ability to control the functions of the body, as well, (and even better) during the most prolonged fast, as when fed the accustomed amounts of "good nourishing food." Relatively to the rest of the body, the brain and nervous system increase as the fast continues, due to the fact that little or none of their substances are lost.
The spinal cord loses less than 10 per cent in death by starvation--the brain nothing. There are almost no structural changes in the brain and cord even in starvation.
"In general," says Jackson, "the brain appears relatively resistant to the effects of both total and partial inanition. Usually little or no loss in weight or changes in gross or microscopic structure are apparent. In advanced stages of starvation, however, and especially in types of partial inanition (beri beri, pellagra), involving neural or psychic disturbances, there are well-marked degenerative changes in the nerve cells."--Inanition and Malnutrition, p. 173.
Here, again, we note a confusing of the effects of actual starvation with those of inadequate diet so that the statement is a bit misleading. We must also emphasize again that losses seen in starvation are not seen in fasting. It is well always to keep the distinction between fasting and starving in mind.