I had a friend who did the master cleanse and reported good results. It always freaked me out a bit and I was very scared to contemplate the possibilities. Quite impressive.
One Chan perspective is that the Buddha became enlightened after he quit fasting as an approach. Neither running toward or running from pleasure is the path, the middle way is to run in neither direction.
The Chan fellow's name is Rev. Heng Sure and he reports an unsuccessful 18 day fast. He also has a cool blog that has some good photography.
That brings up the question, do we follow what the Buddha did after he became enlightened, from our unenlightened perspective, or do we do the same things he did on the path to enlightenment.
Another aspect is the Dhutangas a set of monastic guidelines that involve not eating after noon, daily fasting. I'm thinking about trying not to eat between solar noon (12:52p) to sunrise (544a) tomorrow. I'll report in if I follow through.
Bhante Dhammika has an interesting blog as well, and he has a post on fasting.
I listened to a talk by people who walked out of their home without money, food or a phone for 2 days. The three people discuss their different experiences of going forth. They begged and got to eat. The copper moved them along, begging being illegal in Birmingham. They slept on cement one night and then in the park the second night. It seemed like a cool friendship activity, they learned who were the best beggars and confronted many fears.
For me the thought is that like running a marathon or challenging fears by bungee jumping or skydiving, you test your limits and build the confidence needed to push hard for the spiritual life.
In the end, I think veganism is a kind of fasting from the flesh and products of animals, that eliminates many options that the society in the USA like. Not eating after solar noon would also be a perhaps the second best practice. And fasting could also be a confidence-building and healthy thing to do, in the conventional sense where you fast for days without eating.