This is far from heavy and there are few AVs as light on resources as avast, 32MB is far from heavy considering that value is for all the resident shields.
It also depends on what you are doing and where you get the figures from, see image of my current figures (avastUI open and monitoring activity so it will be larger than normal) VM Size is meant to be a better representation of actual use. I have many other applications that use much more than avast.