I think the buffet thing is probably a combination of culture and the fact that men just need more food to survive, in general, than women.

Same with keto--I don't think there's something inherent in our makeup that makes men more suited to keto, and women more suited to fruits and veggies.

If you look at say the Kitivans, the animal portion of the diet may be important, but the calorie content is so low, male-female differences in meat consumption are going to be smallish. In a lot of hunter-gatherer groups, even when the men spent most of their time hunting, most of their daily calorie intake will have come from gathered foods.