Robert Kamau / Getty Images North America 1 / 6
Robert Kamau / Getty Images North America 1 / 6

Blake Lively was only eight months removed from giving birth to her daughter James when she began filming "The Shallows." As she was often in a bikini for the film, she knew she had to get rock hard abs, and she did, but it wasn't easy.

The actress spoke to The Kyle & Jackie O Show on Tuesday to reveal her diet secrets.

"I did no gluten and no soy," she said. "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."

Blake said the removal of soy from her diet was actually the harder than removing gluten.

"[It] seems like, 'Oh, that's really easy to cut that out,' but then you realize, there's soy in everything," she said. "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."

She was able to splurge a little bit on other aspects of the diet.

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

Just no soy sauce, of course!

There were other temptations, too, especially on the set of the movie, but the fashionable actress remained committed to the diet of not having any processed food.

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

Blake and her husband Ryan Reynolds are currently expecting their second child, as well.

"We'd love to have a big family," Ryan told Details in 2013. "We both come from big families -- my parents did four, Blake's did five. A lot of people say it's crazy, but we'll only know when we're there, you know? We'll walk through that fire pretty happily, I think."