well, i did it for 3 weeks, so it was induction an the most rigourous. i definitely lost loads of weight and felt brilliant, however the first few days were awful, got very faint and craving carbs (actually hallucinating about pieces of toast!!- makes you realise how addictive they are) . however in the long run it wasnt for me, im too young to completely banish a whole food category from my life, and if u want it to really work you have to keep at it pretty much for ever. also i found the food just wasnt what i liked, u cant have that many veggies at first, no fruit, and its all meat and eggs. after a while u introduce berries, cheese, and types of complex carbs like soya etc.
so as a crash diet its gd, if u can cope with eating loads of bacon and eggs, cheese and meat all the time! but as a long term diet, it wasnt for me. that said, my mums been on if for 2 years and looks a decade younger, and this really fat woman i knew has completely changed her life thanks to it.
anyway u should always think b4 going on a diet, crash dieting is so bad for you!! but if u jst want to fit into a dress then by all means go for it!
as for side effects, i didnt get the whole bad breath thing but i did feel moody and faint, mainly because i missed eating pasta so much!