You're probably not in the right mood/state to diet now, but is there a perspective for you at some stage to be able to take three weeks AND spend a couple thousand quid? Because, having dieted & regained all my life, I have found a German clinic where I not only lost weight, I got (relatively) fitter, in better shape (all lab tests bearing testimony to it, too), happier, and craving vegetables for something like a year after doing the cure. Do email (shezan at gmx dot net) if you're interested at all!

It's very nice, in a large garden overlooking Lake Constance, they speak all sorts of known languages, with a goodish bit of culture vulturing thrown in, and they're no mad quacks