But come on there has to be a scientist that can equate Superman leaving the Earth to a NaSA Rocket launch and that defies some gravity? Or one or two have scientific theories about their superheroes? And yes the Flash does burn calories because every iteration of him at least has some or couple of issues, shows or whatever that talk about it. Like Batman Dawn of Justice. Flash carries out a large pizza he is eating on. In the CW show they had 1 or 2 episodes where they talk about it his metabolism being off the charts like his sexual prowess is, that is why Sisco comes up with a drug or whatever so he doesn't finish to early. There was an episode where Flash is eating a bunch of big belly burger in front of Thawn in Jail and gives to him. To watch Thawn replies we don't have cows or beef in the future.