Fonty
I have little doubt you could do one long fast to complete your goal. However I have only seen a few recorded fasts like this and would certainly recommend finding a professional to supervise you, at least beyond say 50-70 days.
You can also achieve the same results by doing shorter fasts, maybe still very long ones in themselves, and eating raw food in between. I myself fasted about half of the last four months of 2007 in fasts of varying lengths and eating 90% raw food in between. I lost 40 kgs over that time and have kept that off and a bit more since.
You aren't losing any time doing it this way really because if you eat properly in between you won't be interrupting the process as much as continuing it a different rate. And if you fast for 100 days straight you still need to allow as many days after for Recovery and Refeeding according to many authorities. The refeeding is just as important as the fast for the ongoing effectiveness of the fast itself and also as a kick-start for the change of life we need to continue to be healthy afterwards also.
Andrew.