It is suggested many times that the reason for the bloating is an increase in the papyrus-section of the savegame (Such is the case for myself aswell). More specifically, left-over scripts from uninstalled mods. I'm not knowledgeable enough about this to delve into it further, but I would think that being able to clean up these, and the error messages they must be creating in the papyrus log, would be a good start to solving this problem.
Bethesda's engine cannot clean up scripts when you uninstall a mod. Say you have a mod that puts a script in a particular piece of apple. After you uninstall the mod, that apple will still have the script attached to it.
This means that with every mod that you install, unless they are the "non-gameplay enhancing" aesthetic mods, as some quest modder calls 'em, they WILL increase your save file, and it will be like that until you start a new game, not placing of scripts in the first place.
I do not know whether it applies to objects that the modder specifically create (for example, if it creates a new object in a new dungeon, which will be gone when you uninstall). But it'd be best for now to think "yes"