This weekend, Breaking Bad’s Bryan Cranston will hit the big screen in a big way, starring as a Ben Affleck’s CIA boss in the much anticipated spy thriller Argo.

And while you might not necessarily see the actor as the poster boy for health and fitness (he is, after all, best known as the emotionally messy chem-teacher-turned-meth-dealer Walter White), he’s definitely in tune with his body —and what he puts inside.

“Bryan enjoys healthy food, so that’s never a battle,” says his nutrition coach, Jackie Keller, who helped him prep for Argo. “In this case, he didn’t really have a lot of weight to lose—there was no low body-fat percentage goal, no definition goal. He just wanted to be in good shape.”

So for Cranston—who Keller says came to her as a meal skipper who would “eat whatever was put in front of him”—that meant coming up with a plan of frequent, well-balanced, portion-controlled meals.

“We needed to keep him evenly fueled, to prevent those peaks and valleys in his energy levels and ability to focus,” says Keller. “At the most, you want three hours in between meals—tops. It can be hard when you’re filming, but it’s doable”

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