I was recently educated by one of the members here that canned squash is a fiber source that cats will eat if mixed with their food. (For dogs, I usually recommend canned pumpkin but my feline patients won't eat it). The mechanism of action for commercial 'hair ball' formulas is just additional fiber. The fiber helps move the hair down instead of clumping up into a ball. The other option are the laxative medications like laxatone, Vedalax, and Tonic Lax. Some cats find some formulas more tasty than others and there are usually a couple of flavors available such as malt or tuna.