“It was such a sad story to be taking part in,” she told Closer. “I was crying in nearly every scene, and quite often I’d eat cake to cheer me up.
“I was snacking on biscuits in the green room, or eating flapjacks made by the crew when I was exhausted.”
Katie admitted she was “eating so much sugar” in between scenes, and was having a lot of diet fizzy drinks.
“I was usually between a size eight to 10 when ordering clothes, but I was creeping up to a size 12, which isn’t bad at all – but it was bigger than I usually am,” she said.
“I wasn’t fuelling myself properly and I’d put on over a stone.”