I'm unsure on calary i presume there would be some form of calories in calary ? but yeah bro it all depends how your everyday life pans out , when I fasted I was doing 5 - 11 , I'd have school during...
Yes it does bro , your body's notices its not getting fed for a long period of time what do you think it's going to do ? It's going to use stored energy (fat)
If done a 2 month fast was real easy cutting body fat , I wouldn't reccomend jumping straight to 20 hours though I'd take it slow start at 16 - 8 few weeks later 18 -6 few weeks later 20 - 4