It doesn't go back to normal at all . . but what you may be seeing is tumors or fluid filling up in the belly. It's not normal.
The following is a graphic photographic account of a mother's journey with her dying child. The images won the 2007 Pulitzer Prize for Feature Photography:
http://www.sacbee.com/static/newsroom/sw...

If you could explain the last part of your sentence "why does your body go back to normall before you die? ", I would be interested in the details. Would you re-post this question and give the details of your meaning of 'return to normal'. If you are referring to weight, you are mis-informed. Lost weight is not miraculously regained.Therefore, what has returned to "normal"?
I await your re-posted explanation
matador 89