shadowvalkyrie and I were puzzling over Sam's inexplicable fatness, which prompted me to create a new post for Sam and other people with freakish biology in ASoIaF.
Sam spent weeks marching and weeks starving and he's still the one of the fattest men Bran has seen?! WTF, GRRM?!
The problem with Gregor's size isn't his size but the fact that his size gives him no problems. His headaches may or may not stem from physiological problems related to being a giant, but otherwise he's fine. Most really tall people are usually thin, but Gregor is as muscle-bound as he is tall and while he's slow compared to people like Oberyn and Bronn, he's still quick enough to very successful on the battlefield and in tourneys.
Brienne is the female equivalent of Gregor; truly one of a kind. I wonder exactly how big she is.
Dunk. It's stretching credibility that Dunk could grow that big and be that healthy on the very poor diet of a street urchin.
Okay, so Tyrion estimates Gregor's weight at 30 stones/420 pounds but Gregor seems to have no problems finding horses that can carry him. So just how much did Biter weigh if his horse could barely carry him?