I suppose. I always thought Greyback was a bit thinner. And by a bit I mean a lot.
EDIT: Nevermind. I found his description in HBP:
"
Do it," said the stranger standing nearest Harry, a big, rangy man with matted gray hair and whiskers, whose black Death Eater's robes looked uncomfortably tight."
-HBP (p 593, US Edition)
And according to his IMDB he's not doing it. But it could just not be up-to-date yet.