Interesting question. My guess is that, overall, a fairly skinny, wiry body type would be best, but that would vary with the local climate. Look at the difference between Nilotic Negroes (the Masai - tall and skinny in a hot climate) versus the Inuit (more rotund, with a tendency toward insulating fat layers).

Smaller folk will do better when food is scarce, more or less.

It really all depends on many variables, which is why natural selection maintains a good variety of body types within human populations today.

Myself, I could stand to lose ten pounds. Been saying that for years - will get right on it, just as soon as I finish this bowl of ice cream.