Better knowledge of cats' nutritional requirements and the development of foods based on this knowledge are two reasons why cats are living into their late teens and early 20s. A number of degenerative diseases become more common in older cats and nutritional management plays a vital role in controlling these abnormalities. Major changes brought on by aging include a reduction in physical activity, alterations in food consumption and digestive functions, and becoming more prone to arthritis, kidney disease and cardiovascular abnormalities.
It is important to reduce the caloric intake to prevent excessive energy intake and obesity. One of the methods of nutritional management for older cats is switching from free feeding to selective feeding of a specified amount of food each day. A number of "light" or senior cat foods on the market provide fewer calories than most maintenance foods. Also be sure to look at the fiber content of the food, making sure it is higher for your senior cat. If your older cat is suffering from oral changes that affect its ability to eat or chew food, then weight loss rather than weight gain may be a problem. Consult your veterinarian and have any treatable abnormalities addressed and have your cat's teeth cleaned well. Changing to a wet food or changing to a food with higher nutrient concentrations so normal nutritional levels can be maintained with less food may be in order.
Once your cat has reached 9 years of age, it is a good idea to look for age-related changes. Until your cat begins to show age-related changes, continue feeding a quality maintenance food. The average life span of a cat is now somewhere around 18. With further improvements in disease control and nutrition, it may soon be even higher than that.