Changing perspectives on aging and energy requirements: aging and energy intakes in humans, dogs and cats.

A series of cross-sectional and longitudinal studies conducted in humans has shown that aging is associated with a gradual decline in the maintenance energy requirement. Generally, this is equivalent to a total decrement of 20% of young adult maintenance energy requirements and is a result of a decrease in both physical activity and basal metabolic rate. Relatively few such studies have been conducted in dogs, but the results have been consistent. It appears that maintenance energy requirements decline by approximately 20%, and it is assumed that the causal factors are the same as those for humans. The situation appears to be somewhat different in cats, with evidence to date indicating that maintenance energy requirements remain constant throughout adult life. Why cats should be different from other species is not clear, but it is hypothesized that relative inactivity is typical of most cats' behavior, such that there is no obvious age-related change. In terms of feeding regimens for senior cats and dogs, it is appropriate to decrease energy provision for senior dogs by approximately 20%, whereas the energy provision for senior cats should not be decreased.