Nope, it's cultural. If you look at cultures outside of your narrow window (in both time and space), you'll find that the perception of fatness has varied wildly over the millenia.

If it just was cultural then women wouldn't have evolved abnormally thin waists, they have that since men finds it attractive, there is no other reason to have as thin waists as women has otherwise.

Women in every single culture have much thinner waist hip ratios than the male counterparts, suggesting that men like them thin.

Over history being fat wasn’t an impulse control issue. It is now.

If we are wired to detect something doesn’t mean it has to be a first order attribute. Isn’t fat now versus fat then.

Gambling, addiction, setting fires, fighting, chronic lying, etc… some of those are first ordered detectable and some maybe aren’t.