>>90052330Honestly it has more to do with character design than it does in universe explanation.
Superman is this idealistic figure who inspires everyone, it makes sense to make him a body builder looking Adonis type even if he doesn't strictly need to be one physically.
Hulk on the other hand is a lot more monstrous in his proportions because he's meant to be intimidating, not inspiring. Personally I think evil-Superman incarnations like Injustice Supes should be more power lifter and less body builder to be more intimidating and more about raw strength than a physical ideal.
A skinny Superman doesn't really work with the character. Skinny but actually super strong character designs work better for those who are more everyday individuals like Spider-Man. I don't think it works well with Superman's origins, it better fits people who got their powers in some sort of event, and they were scrawny before said event.
A fat Superman I can't really picture just because Superman is again, an inspirational figure and there's nothing inspiring about being fat. I do think a fat but actually super strong and fast Etc. Hero could be really good though, maybe a largely apathetic metahuman who takes a stance of non-intervention and his weight while not physically impeding him is a visual cue for his laziness and apathy.
