Do organisms desire fat or calories? They mostly like the associated taste sensations and associated satiety. As I understand it, there are separate taste receptors for fat and sugar - so it is probably better to say that humans desire some types of fat and sugar than to say that they desire calories.
Why not just say that a purpose of the genes is to bring it about that in an appropriate environment the organism will consume adequate calories - rather than saying that the genes program a desire for fat?
There's little difference - since the way the genes bring about the consumprtion is via desires. FWIW, I didn't just say "fat", I said "fat and sugar" - and they were examples of desires - not an exhaustive list.
"Desire" is a psychological description first and foremost, and only incidentally, if at all, a term of evolutionary biology.
Genes build our desires, though - in much the same way that they build our hearts and legs.
They mostly like the associated taste sensations and associated satiety. As I understand it, there are separate taste receptors for fat and sugar - so it is probably better to say that humans desire some types of fat and sugar than to say that they desire calories.
And by the same token, it is probably even better to say that they desire ice cream and/or the taste of ice cream, and so on for other particular foods. The brain integrates information from the receptors you mentioned together with other taste receptors, smell receptors, texture sensations, ...
The jacket text for Keith Stanovich's The Robot's Rebellion sums up the book well:
The book is an excellent introduction to the first stage of Yudkowskian philosophy: We are robots in a mechanistic universe running on a swiss army knife of cognitive modules. But at least we finally noticed we're robots, and we can use the skills of rationality to hop off our habit treadmills and pursue our values instead. These values are complex and often arbitrary, but we can use our reflective capacities to extrapolate our values based on "higher-order" desires, a desire for preference consistency, and other considerations. All this is argued for at length in Stanovich's book. The only thing missing is a discussion of what to do about all this when AI arrives.