The most I have ever lost in a day was 2 pounds (it only happended twice though) so the max would be 22, HOWEVER that is unhealthy and unlikely (because if you don't eat enough calories your matbolism slows down and you burn less calories) So I would say 4-5 pounds would be a huge accomplishment because doctors reccomend 2-3 pounds a week max. 11 days is a week and a half so yeah 4-5 would be hard enough to do.