In my church days, fasting is done in private. It is a way to concentrate on an issue that needs divine intervention, making a connection to 'Powers that Be', the universe or God. The fasting doesn't change God; the fasting is to change you. A fasting isn't just the denial of food; it can be sleep or time. Actually anything you like, as it is a sacrifice, you use that time read, pray waiting for insight on the issue. In BDSM I would think it would the writings of Gor using it to find what you need or another author that is in-depth in the life style. Hope this helps a litte.