I recently posted a review of Eat Stop Eat. It basically was a 24 hr fast twice a week. That, however, is not the only fasting train in town!
There is alternate day fasting, where you fast on every....you guessed it....alternate day.
There is Fast 5 where you fast until 5pm and then have an unlimited eating window for 5 hours.
The Warrior Diet is similar. (I haven't read the book yet so I don't know the differences off hand.)
Then there is LeanGains. From what I can gather it is 16 hours fasting and 8 hours eating window but it is accompanied by very specific macro ratios. (I have heard he is writing a book. I can't wait.)
And then there are those who wing it!
I have become one of those people.
I was doing the Eat Stop Eat plan but I have not been able to fast for 24 hours since I switched to a ketogenic diet. So I have been experimenting with various lengths of daily fasts. A 16/8 split seems to be the magical ratio for me. I fast until 12:30 or so and then have lunch. My eating window is 8 hours from the time I start eating, usually until 8:30. It has been working so far. My macros and calories have been far easier to maintain.