I myself was actually whirling the idea around in my head a few days ago to rid my body of Meds. Although withdraw would be tough I think I need to do this as the meds no longer work for pain. I thought id I stop all intake except water it would ease some of the bathroom problems that come from withdraw. I don't know if this would be considered fasting as I did have an IV in me but I had not even a drop of water through my lips for 11 days back in 1997 due to a perforated colon. After about a day I no longer felt hungry and I lost 27 lbs in 11 days. I had to be weaned back onto food when it was safe to eat again. It was either do that or have a colostomy performed which would have been reversible in about 6 months I chose the easier of the two.