Just want to add a note for us hypoglycemics and/or diabetics out here: Fasting at the onset of depression can cause a dangerous crash in blood glucose levels, which in turn causes a very real bodily response of inner pain, self-hate, fatigue, moods wings, and eventually, possible coma and death.
I recognize that for folks who believe, prayer is an excellent option for fighting the demon, so to speak, but PLEASE do not fast if you are feeling depressed. Basic human anatomy shows that this can be very dangerous, and even fatal.

"Hypoglycemia, hypoglycæmia or low blood sugar (not to be confused with hyperglycemia) is an abnormally diminished content of glucose in the blood.[1] The term literally means "under-sweet blood" (Gr. υπογλυκαιμία, from hypo-, glykys, haima). It can produce a variety of symptoms and effects but the principal problems arise from an inadequate supply of glucose to the brain, resulting in impairment of function (neuroglycopenia). Effects can range from mild dysphoria to more serious issues such as seizures, unconsciousness, and (rarely) permanent brain damage or death."