@meso @creamqueen a lot of motivational and metabolic energy goes into reproduction, and I'm not just talking about going outside and running around. Sex hormones often cause an animal's body to use more of its reserves-- energy, limited number of cell divisions, etc-- to maintain things like big muscles or uterine linings etc.

Neutered animals are outside of their natural state, yes, and usually that's a net harm. But since we have no need for them to individually reproduce most of the time, we can remove that burden from their system.

Yes sometimes they get fat and ugly and unhealthy in other ways, but they tend to live significantly longer.