I lost an average of 400-500g a day (went from 100kg to 90kg) by eating only once a day (dinner - usually fish or chicken with vegetables) and no regular change to my activities. I did usually have 1 or 2 "cheat" days though, usually over a weekend when we had family dinner and/or when I went out drinking. Sometimes I had an apple for lunch.

I suspect that my body was just "normalising" and after a certain threshold it would probably have become harder to start losing weight without exercising. After I traveled for work my diet got totally screwed up and I went back to 100kg. I'm now on day 3 of the same diet and am currently at 98.5kg. As for my mood, well-being etc, nothing's really changed except for the mild hunger pangs (which I got used to quickly) and that I seem to get drunk quicker when I drink.

This is just a personal anecdote. Don't take it as medical advice of any sort.