A cat's energy needs follow a U-shaped curve: very high in kittens, stable in adults, then increase again after 11–12 years — not because the older cat moves more, but because the body digests and uses protein less efficiently, requiring higher amounts to maintain muscle mass.
Three metabolisms, three patterns
A growing kitten uses roughly two to three times more energy per kilogram of body weight than an adult: building the skeleton, muscles, and immune system demands a steady stream of nutrients, with protein and energy needs relative to body weight remaining high until reaching adult size, typically around 10–12 months.
In a stable adult, food intake serves mainly for maintenance: keeping body temperature steady, moderate physical activity, and cell renewal. Energy needs then align with ideal body weight and change little from year to year, unless activity levels shift.
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After 11–12 years, the picture reverses in a counterintuitive way. A significant proportion of senior cats develop reduced ability to digest and absorb dietary protein, a phenomenon well documented in aging cats. To offset this loss of digestive efficiency, the body needs higher-protein diets made from quality sources, not lower ones, to slow the muscle wasting (sarcopenia) that comes with aging.
The trap of the aging cat that loses weight
This is a common belief worth correcting: when facing a senior cat losing weight, the usual reaction is often to cut calories, especially protein, from fear of "straining" the kidneys. Yet in a cat without diagnosed kidney disease, this restriction worsens muscle loss rather than slowing it, because the animal lacks the protein needed to compensate for its less efficient digestion. Adjusting the diet of an aging cat that is losing weight should be discussed with a veterinarian, who will assess whether underlying illness explains the weight loss before any dietary change is made.
