Cats are pretty savvy about knowing what they should—and shouldn't—eat, so pay attention when your feline starts snacking on stuff that isn't food. Sometimes it signals a bigger issue.
Medical problems: Bring your cat in for a vet check if you notice sudden changes in appetite. For example, an increase in appetite may be a sign of hyperthyroidism in older cats. And eating litter may be a sign of anemia.
Behavioral condition: Cats can have compulsive disorders, where they eat things other than their food or groom obsessively, which causes skin problems. In these cases, seek out a board-certified veterinary behaviorist.
Genetics: Siamese or Birman purebreds are more likely than mixed-breed cats to suck and chew on wool. This can be a serious problem—eating strings could tangle your cat's intestines.
Boredom: Indoor cats may eat odd things for entertainment, such as shoelaces, ribbons and tinsel. Offering puzzle toys, games and playtime can help.