The first one is appetite. The real hunger comes around after a few weeks of fasting - and unlike appetite, it doesn't go away when you do something interesting.
Feeling of hunger is very individual. For some people, it's no big deal. For other people, it is very annoying. I know that if I haven't eaten for a day, I start notice limping people more, and I can't stop watching small children, because I want to kill and eat them.
> Appetite is a feeling I would describe more psychological. I'm smelling something delicious and suddenly want to eat it.
It is psycho-physiological addiction. (smell is not psychology, it is physiological). It is like cigarette addiction. But it isn't a physiological need.
Actually he described it quite well. Appetite is psychological, whereas hunger is a physical sensation of pain.
I'm replying to your post because I get hungry even quicker. I had lunch (rump steak, potatoes) at 1pm and now at 4:30, I'm hungry again. My BMI Is 21, with rather low body fat.
Even with a BMI of 21, you can probably fast for 20-40 days with no irreversible damage, and that feeling you call "hunger" will not be there after the 2nd day.
You do not know what hunger is until you've felt it. I thought I knew what hunger was, until I fasted for 25 days. Then, I actually discovered what hunger is.