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.
With fasting as magic we have nothing to do, except to study the phenomenon. Tribal fasts, as seen among the American Indians, to avert some threatened calamity, or fasting, as by Ghandi to purify India, is the use of fasting as magic. Fasting was widely observed, both in private and in public ceremonials by the American Indians. Fathers of newborn children are required to fast among the Melanesians. Fasting was often part of the rite of initiation into manhood and womanhood or for sacred and ritual acts among many tribes of people. David's twelve days' fast, as recorded in the Bible, while his son was ill, was a magic fast. Ceremonial fasting carried out in several religions may properly be classed as magic fasting. If we carefully distinguish between magic fasting and protest fasting, as in hunger strikes, we may say that magic fasting is fasting undergone to achieve some desired end outside the person of the faster. We are interested in such fasts, simply as another part of the evidence that man, like the lower animals, may fast for extended periods and may do so, not only without harm, but with positive benefit.