Any experience with fasting?

I know that I can google this and wiki that and come up with a general idea of what to expect but I want to hear your experiences with fasting. How long did you fast? Why did you fast? Was it beneficial to you? I am dedicating 2012 to getting my ass in the best shape I’ve ever been in. I want to complete a triathlon towards the end of this year. I already ride and run but not enough….I am healthy but I will still drink and eat gelato and poor, fatty foods…Not this year. I am taking this year to finish first as a triathlete. I am 36, turn 37 the end of March. I’ve had this on my goal calendar to be completed by age 40. I am only competeting with myself. Anyway, I started acupuncture and suction today and will be going two times a week for the next ten weeks. I would like to know if any of you have fasted and if it helped kick start you off to something more healthy, or maybe it is a poor idea? Please share your experiences. Yay or nay?