Isaac Butler in Slate:
The most straightforward way to figure out whether Hamlet is fat is to look at the text itself, in which Hamlet’s own mother calls him fat. During the play’s final sword duel, King Claudius turns to Queen Gertrude and says that Hamlet will win the duel, and Gertrude replies, “He’s fat and scant of breath,” before turning to Hamlet and telling him to “take my napkin, rub thy brows.”
Oh, great! you might think. Hamlet’s fat! Someone get Benedict Cumberbatch on the phone and tell him to start pounding the Big Macs. But just when you thought Shakespeare might, for once, make things easy, it turns out this line doesn’t prove anything. For one thing, there is no definitive text of Hamlet. Most versions of Hamletwe see or read are cobbled together from multiple editions, none of which had Shakespeare’s direct involvement. Gertrude’s line about her son being fat and scant of breath, for example, doesn’t appear in the earliest published edition of the play. We’re also not entirely sure where that first edition (called the “first quarto,” or “the bad Hamlet”) came from. It may be a first draft written by Shakespeare, or it could be pirated by an audience member furiously scribbling the play down as it was performed, or reconstructed by one of the actors who played a minor role in the show.
Maybe the line’s absence doesn’t matter. After all, the bad Hamlet is bad. It’s the version of Hamlet where the play’s most famous speech begins, “To be or not to be, aye, there’s the point.” But its absence in an early version could also demonstrate that Shakespeare added the line about Hamlet being “fat and scant of breath” later, as Richard Burbage, the actor playing Hamlet, like so many of us in our late 30s, got a little fat and scant of breath.
More here.