Without it, two big problems can arise, according to Colleran: Obesity and boredom.
A short list of potential effects of feline obesity, from a 2006 article in the Journal of Nutrition: Orthopedic disease, diabetes mellitus, abnormalities in circulating lipid profiles, cardiorespiratory disease, urinary disorders, reproductive disorders, neoplasia (mammary tumors, transitional cell carcinoma), dermatological diseases, and anesthetic complications.Then there's arthritis. Says the Cornell Feline Health Center: "Older cats frequently become less agile as arthritis develops and muscles begin to atrophy." They recommend "regular moderate play" to stave off arthritis.
Bored cats, meanwhile, "act out other behaviors that are considered inappropriate, like chewing on things, or scratching on inappropriate surfaces," says Colleran. "Sometimes they just plain sleep all the time, and that's no life to have."
So how do you make sure your cat gets enough exercise? Different breeds, and even different cats, have different needs. Some breeds, like the Savannah and Cornish Rex, are naturally energetic, while others, like the Scottish Fold and Persian, are less inclined to exercise. Young cats and kittens have much more energy to burn off, so need more playtime than older cats. So when do you know if your cat has had enough exercise? "When they quit!" says Colleran. How much time that will take, of course, will vary; Jackson Galaxy, cat behaviorist and host of "My Cat From Hell," recommends at least 15 minutes of intense playtime per day.