As someone who is overweight I have come across many diets in my time but this one really stuck in my mind, it promises to help you lose a stone in a week .... A WEEK! Surely this is dangerous? http://www.jaduncan.com/2006/04/how-i-lost-stone-in-week.html
I wonder... are you even alive after that week? Seriously, this is some crazy diet. Being on that diet means being whole week HUNGRY. I wouldn't do it for sure. Starving is unhealthy, in my opinion.
And then what do you do after that week? Maintain that insane intake? Even if you ate healthily afterwards you'd surely add weight again. This is just another in a long line of fad diets. Of course you'll lose weight if you don't eat but then what? Keep not eating? It's not sustainable.
Well apparently you are meant to do the diet for a week and then have 2 weeks off before doing it again. It feels very unhealthy to me.