How to cleanup unused embedded fonts from ODT or garbage collect inside ODT file?

I have ODT file with aprox. 700kb of useful data inside. The file size is 6Mb.

When I’m opening ODT as Zip archive I see inside 10Mb (unzipped size) of 17 fonts in folder /Fonts. I’m using only two fonts. So, in resulting file I have aprox. 5Mb(zipped as a part of ODT file) of waste data inside.

Can not find a way to throw away the embeded fonts. I can copy-paste from current file into new file, save it and it’s size will be 700-800kb. But today there is the common feature “cleanup unused objects from file/internal database/storage” in mail clients, office apllications. I’m searching for similar functionality and a king of garbage collector in Libre/Open Office.

How can I throw away unused objects and embeded fonts from an ODT file? How can I cleanup the file?

P.S. I’m using LibreOffice, Ubuntu 14.04. The question is related to Writer component and ODT files.

Open the document. Copy everything. Paste into a new document. Save it. Delete the old one.