This is a tough one. Most all of the major Religions (except Christianity) teach Fasting. It is believed by many that Jesus Dry Fasted for 40-days in the desert...taking in only the morning Dew. I mean, if you want to solve serious issues through Prayer, you don't want to interrupt that with Food, or even Water.....WY
P.S. Don't try this at Home. Yogis (as Jesus was) know how to slow down the metabolism so very, very little Sustenance is needed.