Fat cats may look cuddly and adorable, but they are at risk for serious illnesses such as diabetes, arthritis, and hepatic lipidosis (liver disease). Some of the most common causes of cat obesity include: hypothyroidism or other metabolic disorders high carbohydrate diets free choice feeding lack of exercise But the good news is that responsible owners can usually turn their fats cats into slim kitties, with a little knowledge and a few fun steps. My Fat Cat sets the record straight on common misconceptions, evaluates diet foods and nutritional supplements, and offers creative, entertaining ideas to help your pet lose weight and live healthy. 20 photos.