Thanks. I read (somewhere) that it takes 2 - 3 days for ketons to completely withdraw. This is why I limited my eating to only one day. Theoretically, on Monday I should still be in 1/2-2/3 ketosis. However, on Monday mornings my tongue is usually pink, instead of white, meaning that cleaning process has stopped. Usually it took the entire day to become white again. This last Monday it became whitish around early afternoon. So obviously ketosis 'recovery' was faster than before.
I have to admit, first two Mondays were 'hungry', perhaps because I binged (whatever I wanted) on Sundays. After that they became more or less as any other fasting day--as if my body 'learned' the pattern.
Before I started fast I was eating cheese for three days so on my first day of fast I was already in ketosis, without that I found an induction phase really hard. The fact is, even when you are in ketosis there are still hard moments and hours, it is just that you've already made some progress and it is harder and harder to give up.