There are three types of domestic cats: indoor domestic cats, outdoor domestic cats, and indoor-outdoor domestic cats. Though these cats would look very similar if they were clean and sitting next to each other, they would also be very different.
Indoor cats are generally very clean, since they do not have to work for their food. The excess time allows them to clean and pamper themselves on a daily basis. The fact that they are usually fed on regular intervals makes an indoor cat overweight. The cats know that they can sleep all day and still get fed once or more times a day. Also, since the cats do not work for their food, they lose their exercise time. It makes it impossible for them to burn off any extra calories they may have gotten.