I found that my Word document with lots of images kept growing and at one point reach 27MB.
I wanted a solution. I ran Document Inspect (File – Check for Issues). It found some Embedded Objects. What is that?
OK. It means that when I pasted images into my Word document, system preserves image as an editable object (similar to Excel file embedded into Word document). Next step for me was to find all these embedded objects and convert them to simple images.