The Showgirls star had an unusual reaction to one serving of oysters in New Orleans, Louisiana and discovered she had fallen ill with a bout of food poisoning.
It took Gershon a little while to recognise the full affects of the solvent on her face as she had piled on a few extra pounds to play Sharla Smith in the film.
She tells New York Magazine, "It's more fun to look super-gnarly (ugly) that to have the pressure of looking beautiful. I don't like doing things halfway. My character lives in a trailer and drinks beer and eats all the time. That wasn't fake - that double chin was mine, babe...
"My face was blowing up, and I kept thinking, 'Wow, I must be so method'. It dissipated after three months, but my face had these lumps in it. Luckily I was playing someone who could look like s**t."
But Gershon admits it was still a shock to see her full transformation onscreen and she immediately set out to get back into shape as soon as filming wrapped on the gritty crime thriller.
She says, "I was like, 'Oh my God. I'd better start losing weight immediately. I have to look OK before I do press, because people are going to think, 'Oh wow, she really let herself go'."