Messages taking up memory on iPhone?

I have an iPhone 4S and I've recently just updated it to iOS 7.

A few days ago I was having a clear out on my iPhone and noticed that Messages is hogging 2.9GB of memory. When I tap "Messages" it says "Messages (Saved)" and I can't delete it. I can delete messages and conversations from within the app though.

But I can't understand why this is taking up 2.9GB! I never had this problem with iOS 6.

Any suggestions? Or has anyone else noticed this?

Thanks in advance.

Added (1). Also, to be clear, I don't think I've ever deleted an SMS or iMessage from my iPhone 4S since I first got in (back in August 2012) - could this be why? I've had a lot of media (images and videos) sent to and from my iMessage conversations over the year - maybe media has built up? Although I thought only the last 10 bits of media was temporarily saved on your device… Then deletes itself after a while?

My own messages takes up 14MB. If yours really takes up that much space, check your messages app. See how many text messages and conversations you have going in there. You might want to consider removing some of these.
To do so, click on the top left, on "edit", then just click on the little "-" to the left of the conversation, and it should pop up with a button on the right that says "delete", just tap that and it will remove the conversation, thereby clearing some room on your iPhone.

Try a cache cleaner app