Apps taking up to much space

According to iTunes my apps come to over 7GB. I know checking "Usage - Storage" this is about 5GB too much. Therefore 5GB is effectively unsuable

My camera roll is 800mb so it is not photos.

This was a new iphone which was restored from a backup, so i take there is an app on the backup that is corrupted and hogging the space??

I hear the way to fix the problem is to setup as new device and not restore from backup, but then all my photos/ notes/ messages/ numbers will be lost using this method?

Any idea how to fix?