he says you'll lose between 0.5 to 1lb of fat per day, not factoring in metabolic slowdown. For some, slowdown kicks in at 3 to 4 days. For the lucky ones, it can take 2 weeks.
Lyle is honest about it all, in his book. He says a LOT of what you'll lose will be water and glycogen. You do risk losing muscle. And you will feel like crap on it (hunger, mood swings, anxiety etc.).