>>3371It's definitely muscle. Remember that Samus isn't a normal human- she's got Chozo blood. It's very possible for her to put on more muscle than a normal human woman is capable of putting on.
I figure in 'real life,' outside of her fetishy portrayal in certain games, she's built a bit like a linebacker, but she's still got nice thick hips and decent-sized tits.
Or maybe more like a safety.
Still, it's fun to fat her up a bit.