"How did you get so big?
Did you eat too much
Did you bite off more than you could prove "

I think he had a girlfriend who became famous and forgot all about him. When he talks about her being 'big' I think he means her ego, not her physique.

"So Hollywood
Riding with the stars
And all the regulars know
Just who you are "

This just restates how she became famous or got noticed or something like that and left him.

"I've got the biggest heart
You've ever torn apart "

I think he is trying to remind her that he has been the nicest guy she has ever dated, so it's not like her deserves to have his heart broken.

"How did you get so drunk?
I guess you had enough
You swallowed more than we all knew "

Now that she's famous, she parties too much.

"So many friends
Only hold you when
You got dreams for them to sink
Their teeth into "

Her friends are in show business, and they only want to be nice to her when they can make money off of her.

When he sings about fooling with the wrong guy, it might just be me, but it sounds like he might want revenge of some sort. Who knows?