I don't have a lot of knowledge but personally I wouldn't. When your body is deprived of the nutrients you will get hungry after a long fast and you need to eat then. I think it will disrupt that somehow. I did download a pdf from this forum on fasting that said your body moves the stored nutrients around to the right place and makes good use of it. I will include the link to this free e-book very informative
. http://jeune-et-randonnee.pagesperso-orange.fr/devries.pdf