File size increases significantly with Macros

Hi:

I have an excel wookbook (excel 2010) that has a small macro (15 lines of basic look and replace) attached to it. The file size is 25 megs, but if I remove the macro, the file size decreases to 6 megs... Is there a way of keeping the file size low and still have the macro attached to the file?

Thanks for any help you can provide.