Before recommending a diet for a senior pet, a thorough nutritional evaluation should be completed. Although many middle-aged and older pets are overweight, a large percentage of geriatric cats and dogs have a low BCS. Approximately one third of cats older than 12 years of age may have a decreased ability to digest fat, whereas one in five may have a compromised ability to digest protein. Thus, appropriate diets for these two age groups may differ considerably. Mature (middle-aged) cats would likely benefit from a lower calorie food, whereas geriatric cats (>12 years of age) may need a highly digestible nutrient-dense diet. More than 40% of dogs between the ages of 5 and 10 years are overweight or obese. Such dogs may benefit from diets with lower fat and calories. Senior dogs also have an increased need for dietary protein, however. Therefore, healthy older dogs may benefit from diets with an increased protein-to-calorie ratio, providing a minimum of 25% of calories from protein. Common obesity-related conditions in dogs or cats include DM and OA. Diabetes differs between dogs and cats. Type I diabetes, common in dogs, seems to respond to fiber-enriched diets, whereas type II diabetes, common in cats, seems to benefit from high-protein and low-carbohydrate diets. OA, an inflammatory condition that occurs in approximately 20% of dogs, may benefit from weight management and nutrients that reduce the inflammatory responses, such as long-chain n-3 fatty acids.