The amount of dietary protein needed to optimize lean body maintenance has been an elusive topic in companion animal medicine. Work in humans and dogs suggests that there is at least a 50% increase in the dietary protein requirement in elderly dogs and potentially even more in those that are exhibiting age-induced sarcopenia, resulting in an adequate protein intake of 5.4 g/kg body weight. Cats, as true carnivores, may accrete lean body mass due to dietary protein well beyond the threshold for dogs, with assumed needs of at least 6 g/kg body weight if not more for healthy elderly adult cats.