I am a huge Brando fan and just finished reading William Mann's Brando Biography.
You can't separate that he wasn't just a genius actor but an incredibly beautiful man physically that every man and woman in his theater days wanted to sleep with and he indulged.
To me, it sounds like he was a sex addict turned food addict. Most days he would eat a whole thing of ice cream.
I think DiCaprio has passed him though from the strength of his films. Brando has some absolutely classic roles but damn does he have a ton of shitty movies.