updated 08/25/2015 AT 8:16 PM ET
•originally published 09/24/2013 AT 8:00 AM ET
Wearing a floor-length Romona Keveza gown, Gunn, 45, showed off a very different look when she took home the Emmy for best supporting actress on Sunday for her portrayal of a teacher-turned-meth-kingpin’s wife on the AMC series.
“I was actually ill while I was filming the show and it affected my weight,” Gunn told PEOPLE at the Governors Ball after the awards ceremony. “They gave me cortisone and I puffed up and gained weight. Now I’m better, thank God.”
Though she declined to disclose further details as to what she suffered from, the now healthy actress added, “I’m doing fine, thankfully. I’m feeling really good.”
As for staying in shape, she credits her figure to her two daughters, who received a shout-out in her acceptance speech.
“I run around after two kids!” she said. “And I do Pilates.”