I just completed my first 5 day water fast for 2015! I feel much better now. I have been doing water fast off and on for the last 20 years. I started with a 3 day fast and have done up to 12 days fast.
I learned about fasting from my Karate instructor Tsutomo Oshima in Southern California. He fast for 30 days every year to heal and rejuvenate his body.
This time was a very different from the previous time. The first 3 days were normal. As my body switches from using the energy from digestion to cleansing, healing and rejuvenation; everything becomes very still. Time for me seemed to slow down as I went through my day. On the 4th day my shoulders, lower back and I experienced a throbbing headache. As I layed down to rest, I could feel surges of energy pulsing through my body and healing me. The next day I was back to normal.
If you are interested, here is some information about fasting.