Abishag has been dieting (reluctantly), but could still use a little less weight on her arthritic hips. This Mother Nature Network article from a few years back has some great ideas to make puzzle feeders for cats!
http://www.mnn.com/family/pets/stories/try-this-diy-puzzle-feeders-for-cats
She always enjoys a treat, and these puzzles will help keep her thinking sharp too.