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 no evidence of any loss to the bones during a fast. Indeed, as will be shown in another chapter, they may even continue to grow while fasting.
When we observe the marrow of the bones, however, we notice a remarkable change. Marrow is stored up food and readily drawn upon for nourishment when no food is eaten. In starved calves, for example, the marrow is reduced to a watery mass. This, amount, of change, however, does not occur during an ordinary fast.