Some options are -
1) Change tiles for something lighter.
2) Remove existing and replace with plasterboard/tiling board. Plasterboard holds upto 32kg per M2, tiling boards hold even more. Think about the wet areas, plaster and plasterboard don't like getting wet.
3) Leave existing in situ and overlay it with a 6mm tiling board glued and screwed/washers to existing studs.