Ours get fed the same - half a pouch each in the morning, and the same in the evening, and they get biscuits to graze on all day.
George is a little tubby, because he was overeating when Edward was sick, and just after we lost him - that's now stopping, and he's getting back to normal (if it weren't, he'd be going on a diet!). Also, Edward was pretty much only drinking cat milk for the last couple of weeks, and George kept sneaking the leftovers while I was sorting out Ed, and before I had chance to move them
.
Magnus eats biscuits like a horse (or hungry cat), but never puts on weight. He's very thin and lean. Not skinny any more though - he was when he got here, but then he was a stray.
But George is a housecat (albeit one who runs up and down stairs all day), and older - Mags goes outdoors and runs about - and is generally younger and much more active.
George is at that stage where he'll play with you if he feels like it, but otherwise he looks at you with complete disdain, as though you've just asked him to eat his own poo or something similarly icky.