Blake Lively Reveals How She Got in Shape for 'The Shallows'

08/16/2016 03:17 pm EDT

In Blake Lively's new film, The Shallows, the actress spends largely the entire movie in a teeny orange bikini, so it makes sense that she'd want to look her best for the role.

As Lively had given birth to her and husband Ryan Reynolds' first child just months prior to shooting the film, she didn't have a whole lot of time to get in shape, but Lively's role required her to be at her physical best.

To get ready for shooting, Lively endured a rigorous training schedule, and she also followed a strict diet that required her to watch her intake closely.

In a telephone interview Tuesday with Australian radio hosts Kyle and Jackie 'O' Henderson, Lively revealed that she cut out gluten and soy while in preparation for her role, noting that it was more challenging that one might think.

"I did no gluten and no soy," PEOPLE reports her as saying. "Once you remove soy, you realize you're eating no processed foods. So that's basically what I did. No processed foods and then working out."

"[It] seems like, 'Oh, that's really easy to cut that out,' but then you realize, there's soy in everything," she added. "Like, everything you eat, there is soy in it. Even if it's healthy, Whole Foods-organic stuff, there's always soy in it. Just try no soy and no gluten and watch how hard that is."

Despite those limitations, Lively revealed there were still plenty of things she could enjoy.

"I was still able to have sugar and all of those things," she explained. "It's all in moderation. You just have a balance of protein, carbs, and vegetables. And it wasn't the worst. Like, I was eating rice and sushi."

The actress did admit, however, that it was pretty difficult to resist the food set out for the cast and crew of The Shallows.

"That was the hardest part," Lively said. "They were making these fresh muffins every morning – those jackasses. They smelled so good!"

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