you can eat up to 500 to 600 cals the days you fast ...fasting have some benefits to clean your inside for your body as well specially if you decide on those fast days to not drink cafeine etc...
i usually have 100 up 150 cals for breakfast
lunch is about 2oo
and i keep most of my cals ( 300 about ) for dinner as we like to always to sit down with the kids for dinner .