Life expectancy for cats has risen, on average, to 14-16 years of age. We are living in the (human) generation which overall sees the benefits of the acceptance and compliance of the general "cat owning" public with our recommendations in vaccination protocols, nutritional counseling/the availability of nutritionally balanced feline-specific diets, and dental hygiene. And, while we can always focus and expand our client education efforts, the veterinary community, and to a great extent industry, have done a good job in client education! We should be proud of ourselves.

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Aging is a complex process reflecting increasing damage at the cellular and organismal level. To paraphrase from Robbins: Aging begins at the moment of conception, involves differentiation and maturation and, at some point, leads to the progressive loss of functional capacity characteristic of senescence ending in death. This occurs at an organismal level as well as at a cellular level. The former may be affected by genetics, social environment, nutrition, and the occurrence of age-related diseases. Cellular aging, on the other hand, includes progressive accumulation of sub lethal injury (e.g., from free radical damage), resulting in either cell death or diminished capacity of the cell to repair itself. We can impact these changes to some degree through nutritional intervention.

What happens to body composition as cats age? Maintenance energy requirements (MERs) vary with age, genetic potential, health status, and gender (intact or altered). MERs decrease with age in humans, dogs and rats. In cats, interestingly some reports no change; when evaluated over longer periods, it has become apparent that MERs decrease until about 11 years of age. After this point, however, MERs per unit body weight actually increase.

Cats in the middle ages ("senior"), under 12 years tend to overweight or obesity as energy needs decrease without concurrent decrease in energy intake. Lean body mass (LBM: skeletal muscle, bone, skin and organs) decreases in cats, just as it does in other species, with advancing age. As LBM is a primary driver of metabolism, all decreases in activity result in reduction in MER.

Studies in geriatric cats over 12 years of age show that fat digestibility decreases with age. Additionally, approximately 20% of cats over 14 years of age have reduced protein digestion. This is of clinical relevance when we try to design the optimal nutritional regime for our older feline patients: protein and fat restriction may well be contraindicated. Especially if underweight, older cats will benefit from a more energy-dense, highly digestible diet to help offset these age-related digestive and metabolic changes.

Key to determining the appropriate diet for any given individual is a nutritional assessment. This should include determining not only body weight at every visit, but also identification of body composition, most practically by using a body condition score. Percentage weight change determination is helpful in detecting trends and alerting both the practitioner and the client to incipient (or blatant) physiologic alterations. Use of a simple diet history form provides important information by revealing not only food fed, but also brand and quantity and treats or supplements that this patient may have access to.