In an exclusive interview with Digital Spy, the former Coronation Street actor said that he was often filmed eating after it became apparent that his character was a recovering alcoholic.
"The thing I learnt about alcoholics is it's not the alcohol they crave - it's the sugar," he said. "That's why Ronnie always has jelly beans! I ended up putting on a stone and a half for the role!"
Walsh added that he hopes the franchise can crossover with the US edition because he would like to meet the American cast.
"We'd meet Epatha and Sam Waterston and I'd hook up with Linus Roache, because of course I worked with his dad Bill on Coronation Street," he said. "That would be wonderful to go there - to New York!"
> Click here to read our full interview with Bradley