hi
diet soda is better than regular soda, its the sugar in the regular soda that makes u fat, diet soda is not healty if u drink very,very,very mutch of it becouse of the aspartam thats in diet sodas.
if u want to loose weigth, walking in a pretty high pace is a VERY good way to loose weight.
if u dont loose the weight its possible that u dont eat enough, try to eat moore, healty food not junkfood
Good luck,