The act of eating a non-food item is called Pica, No one knows exactly why some cats exhibit pica behavior. Because pica has been associated with a variety of diseases, including feline leukemia and feline immunodeficiency virus, a veterinarian should examine any cat with pica. A genetic component is also suspected, since wool or fabric sucking/chewing is more commonly found in Oriental breeds such as Siamese cats. Although it is normal for cats to eat small amounts of grass, consumption of large amounts of plant material such as wood may be an indication of a dietary deficiency or illness. Once medical causes are ruled out, behavioral reasons for pica can include boredom, attention-seeking, attractive odors, hunger, and learned behavior.
Once your veterinarian has ruled out medical causes, you can discuss what steps you can take to modify your cat's behavior. These may include the following:
Food-dispensing toys, durable cat toys, or pieces of rawhide can be used to redirect your cat's chewing behavior to more appropriate and safe items. You might provide her with small flowerpots of grass or catnip that can be planted and kept indoors. You can also purchase "cat greens" at pet supply stores. Having one of these to chew on may help with the wood chewing problem.
Many cats chew on household items out of boredom. Provide interactive toys and set aside time each day to play with your cat. You can purchase a Cat Sitter DVD that entertains kitties as well as many types of cat toys such as laser pointers or kitty teasers.
It may also help to increase the amount of fiber in your cat's diet. Besides providing more dietary fiber, high-fiber foods usually contain fewer calories. Your cat may be able to satisfy her craving to eat more while still maintaining her weight. Consult with your veterinarian before making any changes to your cat's diet.
You can buy spray-on products at pet supply stores that are distasteful (but safe) to cats. Occasionally, applying one of these substances to an item may deter a cat from chewing it. You could also try spraying a strong-smelling substance (such as citrus air freshener or potpourri) or using a physical deterrent (such as an upside-down carpet runner) around an object to see if it prevents your cat from approaching the object-in this case your chairs
If your cat continues to ingest nonfood items despite all your efforts, get a referral to a veterinary behaviorist.
Further environmental and behavior modification plans, specifically tailored to your pet, may be needed and, in some cases, medication may be helpful. Please let me know if I can assist further.