Optimize your SVGs with the awesome svgo.
Grab the latest zip-file for your platform here and extract it to your plugins directory. On my system, I went to "preferences" and it showed this as "User extensions" under "System":
$HOME/Library/Application Support/org.inkscape.Inkscape/inkscape/extensions
So, I used that path.
Find the option SVGO Optimized SVG File (*.svg) under File/Save As.
I use pkg to compile a ready-made runtime so it's a bit easier to install.
Run make to build these.