I once went for five days without eating anything but B complex pills...of course I was a teenager. I lost weight too, but of course I do not recommend it.
I also remember "food combining" where you are supposed to eat carbohydrates separately from protein, because they get digested differently...it drove me crazy, and I decided that in prehistoric times, people pretty much ate what they could find, when they could find it...and that was the end of that!
One thing I did like was when I tried the Neanderthin type of diet, only everything had to be raw...so all I could eat, meatwise, was smoked salmon and proscuitto. (It was something called the Instinctos.)
I lasted about two weeks, felt pretty good, but detoxing so fast clogged my sinuses something fierce! I thought my face would explode.
But even now, I prefer my veggies raw, and I LOOOVE smoked (uncooked) salmon. So I'm doing a kinda Neanderthin thing still (except for coffee and cashews...I would really miss those...)
Thank heavens for Dr. Atkins!