the way I would do it is have a separate item for each stage of its consume, and have a common event that is called when it is consumed, this would probably be better than just using a variable detecting how many times it has been eaten as imagine you have 4 consumes, you consume twice then sell that item or remove it from the inventory in some means or other, when you use a fresh item it will still be on the same consume count, so you could just do it in seperate items ie:
whole bread: when eaten removes 1 of whole bread and gives 3/4 of bread
3/4 of bread: when eaten removes 1 of 3/4 of bread and gives 1/2 of bread
ect
1/4 of bread: when eaten just removes(its fully used)
that way you will have to make more items but its more managable