Be very careful with the fat fast! Dr. Atkins warns against using it, unless you are severely insulin resistant. Even then, he doesn't recommend doing it for more than 2-3 days, because the lack of protein causes muscle deterioration, which I'm sure none of us want. Moreover, I suspect that switching between fat fast and regular LC wreaks big time havoc with your metabolism.

If you're looking to jumpstart your weight loss, many on this board have recommended KISS. It's a more restrictive version of Induction based mostly on pure protein and fat sources. Try searching the forum for more information.