I'm still in the research phase but I did Medifast four years ago and faced a similar question about telling people. If some people thought a fasting diet was drastic, wait till they hear about this!
Anyway, my reasons for keeping this to myself is mostly because I have a family of "know-it-alls" -- and I say that in the most loving way possible, because I tend to be one, too. They will love and support me but if something goes against their views, they have no hesitation to speak out, even when they don't have any knowledge on the subject -- just opinions. My husband and my children, thankfully, aren't like that. They may have questions but they're not trying to debate me. They know that if I'm considering something, that I have or will do the research. I'm not into fads and my research into Lap-Band Surgery has convinced me that this is not a fad.
I also like keeping it to myself because part of the fun of losing weight is when others notice. I know they're not just trying to be nice if they comment on my weight loss without knowing what's going on.
I will eventually let people know if I choose to do this but I will tell them on my schedule and I will be proud to tell them!