[Commenting on a correspondent's letter, H.P.B. wrote:]

The Rationale Of Fasts

H.P. Blavatsky

"The rationale of fasts lies on the surface. If there is one thing more than another that paralyses the will power in man and thereby paves the way to physical and moral degradation it is intemperance in eating: "Gluttony, of seven deadly sins the worst." Swedenborg, a natural-born seer, in his "Stink of Intemperance," tells how his spirit friends reproved him for an accidental error leading to overeating.

    "The institution of fasts goes hand in hand with the institution of feasts. When too severe strain is made on the vital energies by overtaxing the digestive machinery, the best and only remedy is to let it rest for some time and recoup itself as much as possible. The exhausted ground must be allowed to lie fallow before it can yield another crop. Fast were instituted simply for the purpose of correcting the evils of overeating. The truth of this will be manifest from the consideration that the Buddhist priests have no institution of fasts among them, but are enjoined to observe the medium course and thus to "fast" daily all their life. A body clogged with an overstuffing of food, of whatsoever kind, is always crowned with a stupefied brain, and tired nature demands the repose of sleep.

    "There is also a vast difference between the psychic effect of nitrogenized food, such as flesh, and non-nitrogenous food, such as fruits and green vegetables. Certain meats, like beef, and vegetables like beans, have always been interdicted to students of occultism, not because either of  them were more or less holy than others, but because while perhaps highly nutritious and supporting to the body, their magnetism was deadening and obstructive to the "psychic man."" 

(The Theosophist, Vol. IV, Nš 4, January, 1883, p. 88)
(CW, Vol. IV, p. 296-297)
["H.P. Blavatsky Collected Writings", Volume IV
(1882-1883). TPH, Wheaton, USA, 1981. 718 p.]