on water...yeh. its too much. you would have to go over 3 days or over 10 days.
10 days is the max amount of days recc. for water fasting
3 days without supervision.
i suggest start with a three day Water Fast and then move onto juices to continue to lose. if you break eat well in between because your metabolism is going to be at 75% strength for up to 6 weeks.