The zero length files will slow the backup, the backup command will only know a file is empty once it has opened the file and I suspect that it will have to backup the Inode to ensure the file exists if restored. If these files are not required when the system is restored I would either filter them out during the find or exclude the directories where the empty files exist.

Only find non-zero length files: -
find / ! -size 0 > file
(Note this will also miss out any other 0 length files on the system, i.e. device files, named pipes, etc.)

exclude files by name: -
find / ! -name "filemask*" > file
or
find / | grep -v "filemask" > file

exclude directories: -
find / | grep -v "/dirname/..." > file

I would also miss out the /backup directory as the backup will contain a partial backup file.

Hope that is helpful.