Credit: Gustavo Caballero/Getty Images; Michael Buckner/Getty Images

Brandon Davis -- who once crudely called Lindsay Lohan "fire crotch" -- is now going after his ex Mischa Barton.

After spotting her at a Nylon magazine bash in L.A. Wednesday, Davis (whose nickname is "Greasy Bear") Twittered: "Omg. Just realized my ex turned into 1 of the fattest people in the planet. I'm gonna start dating plus size models. Not! Mischa the heifer."

Barton, 24, has long been bullied for her weight.

Last year, she blogged: "One minute, I'm too fat, the next I'm too skinny."

Bloggers recently heckled her for exposing her tummy and wearing unflattering high-waisted "banana pants."

When photographers recently quizzed her about the getup, she laughed. "That was my Easter outfit," she told them. "You guys shouldn't be photographing me if you don't like what I wear!"