I was at a burger joint last week that has lots of burger-related memorabilia. One of the pictures was of three 1940s/1950s-style cowboys (jeans tucked into boots, ‘cowboy shirt’, etc.). Two men of normal build are on either side of a seated man in a white cowboy costume. The seated man is enormous, and he’s getting ready to eat a burger that’s looks like it’s a foot and a half across. The burger shack behind him is Buffalo Burger.
I don’t know where the photo was taken. I don’t know when the photo was taken, but I suspect it was sometime in the early-to-mid-'50s. I tried to find an image, and I found a rodeo cowboy known as ‘Mr. Six-By-Six’, but I’m not sure that’s the guy.
Your question has clearly been answered, but I’d like to point to another period image of a “fat” cowboy.
William Conrad had a magnificent voice, and he played Marshall Matt Dillon on the original radio run of Gunsmoke. He wasn’t as big as he’d get later on, when he played Frank Cannon and (for a bit) Nero Wolfe, but he was still bigger than average:
http://media.gettyimages.com/photos/radio-program-gunsmoke-featuring-william-conrad-image-dated-february-picture-id534302332?s=594x594
…in fact, executives clearly thought he was too big. When they cast the role for TV, it went to the taller, slimmer James Arness.
The same thing happened to Conrad when he played the title role in the 1948 radio adaptation of Leninger and the Ants*. When they made it into a film in 1954, the part of Leninger went to taller, thinner Charlton Heston. But at least Conrad got a role in the film, as the Commissioner.
*Conrad played Leninger. Not an ant.
I suppose you know this, as you’re from LA, but you see that one guy with a name on his boots, Gene Clark, he built the Buffalo Ranch, which was literally a ranch of bison in Newport Beach. I tried to find some info of where it was, maybe the Buffalo Burger stand pictured still existed I thought, but it’s long gone. It was located somewhere near MacArthur Blvd, Bonita Canyon, and Bison Ave, but it shut down in the 60s and though bison still roamed for a long while after, it’s been built over many times since.
These facts were found on this 15 year old thread here.