I’m really getting into John LeCarre’s spy novels, especially the ones featuring master spy George Smiley. If you’re unfamiliar with him, he’s described as being overweight, sloppily dressed, and a genius. His enemies underestimate him, and usually find out they’ve been played—they’re just pawns on his 3 dimensional chess board.
Not sure if he is a hero, but Nero Wolf was certainly overweight. He was also very fussy about food, cars, women, beer, and working too much. And he was contentious with not only the police, but with his clients. Only a genius could get away with that!
Mr. Incredible, at least before his workout montage.
William Conrad played the title character in the TV detective show Cannon.
Never seemed to slow down Hercule Poirot, so far as I could tell.
Let’s not forget Big Bertha from Marvel comics (X-Men?). Her superpower is to make herself, well, overweight… her fat is like a super strong shield.
And she goes bullemic to get back to normal.
(I read a comic with her at summercamp once. It was pretty weird.)
Nero Wolfe was the first character I thought of.
And then, perhaps since my mind was going in a mystery-novel direction, I thought of Jupiter Jones, from the Three Investigators books I loved when I was a boy.
Little Lotta. Somehow, being overweight gave her super strength.
Great Lakes Avengers.
Mma Precious Ramotswe from The No. 1 Ladies Detective Agency.
Elvis Presley, as played by Bruce Campbell in Bubba Ho-Tep, was in his stouter years, at least at the start.
Possibly ineligible as formerly comatose, not-dead Elvis in a nursing home is not a fictional character.
Perry Mason, especially in the television series.
Dashiell Hammett’s “Continental Op” character (appearing in Red Harvest, The Dain Curse, and numerous short stories) was described as short and fat.
Obelix from the Asterix comic books. He loves to eat and polishes off several wild boars in one sitting.
Bouncing Boy, of the Legion Of Superheroes.
Bite your tongue. She’s just “traditionally built”.
Sir Henry Merrivale and Doctor Fell, both created by John Dickson Carr.
Detective Inspector Andy ‘Fat Andy’ Dalziel in the Dalziel and Pascoe series of detective novels by Reginald Hill, and played by Warren Clarke in the TV adaptation.
Not in the movie " Master and Commander: The Far Side of the World", but in the books Captain Jack Aubrey was described as overweight, and I seem to remember the book saying that sea captains tended to be overweight in general. I think it might have been a status thing-- showing you were prosperous enough to afford to eat and drink too much.