Fat "character" actors have been around for a long time, in
Hollywood.

Jackie Gleason, on "The Honeymooner's",
Chill Will, the raspy voiced comedy sidekick in a lot of early Western
movies. (Stagecoach was one).

More recently, the black fat kid on "What's Happening?", both Jim and
John Belushi, Star Jones, (just had her stomach stapled finally, this
year), Mama Cass, (of the Mama'a and the Papa's), and Carol Mannheim
(excellent actress, but really big).

Oprah Winfrey is probably the most famous, and most visible,
overweight person. She worked like crazy to lose all her fat (very
successful), but then slid back to a more comfortable weight because
it took so much effort and time to stay slim, she said. She actually
ran in the NYC marathon one year, in a very tight spandex track suit.

Richard Simmons used to be the fat grape in the Hanes Underwear
commercials, and has made a career out of helping people avoid his own
dieting mistakes (he lost most of the hair on his head from too little
protein and vitamins on a crash diet he undertook).

I'm sure I've missed a bunch, though. It's always been easy for
Hollywood to stereotype fat actors. Perhaps because there are so few
roles available for them, unless you're already a well known talent.
Seems it's a common screenwriter's crutch. Can't remember but two
"heroic" roles for a fat person. Carol Mannheim's character as a TV
lawyer, and Steven Seagall is pretty heavy in "Belly of the Beast".

I take that back, John Wayne had a lot of weight in his last few
films, like "The Cowboys", etc. I felt sorry for the horse that had to
carry him
around, he must have been 300 lbs., plus with a gut like that, and
being 6' 4" tall.

In the population itself, I'd have to give the nod to the early 1980's
as the real start of the fat parade in the USA. Gym classes were
changed from being fitness oriented, to just being "activities", like
walking around in your street clothes for 20-30 minutes. (No kidding).
Most coaches were let go to save money, unless they were involved in
an "essential" varsity team (baseball, basketball, football). Fast
food was all the rage, kids were bombarded with "Sugary" cereals
during kid's cartoons on Saturday morning. Video /Computer games were
becoming popular as well.

I believe the only thing that slowed down the spread of the fat, was
the incredible popularity of Running, in the 1970's and
1980's.Unfortunately, that exercise, while great for burning calories,
(and it's own source of a high), also left you prone to injuries,
before too long.

During WWII, Hermann Goering (Head of the German Luftwaffe), was huge.
People blamed him for the blitz in London, etc. Naturally, it was the
very thin Heinrich Himmler and his very handsome and thin assistant
who came up with the plan to round up and murder all the jews,
communists, defeatists, etc., from Adolph Hitler's idea's. The sight
of Goering trying to waddle around in his pretty uniform and leather
coat, or worse yet, to see him actually try to shoehorn himself into a
plane was a bit of a howl.

Worse image I've seen for stereotype of a fat person:

Norbrett and Big Mamma, (Big Mamma's House, maybe?)

Those were all done with costumes, but they look VERY real, right down
to the dimpled fatty thighs, and they're the worst stereotypes I can
even imagine.