Alicia Vikander—who stars in the new Tomb Raider movie (coming out March 16)—has so many abs, it’s hard to count ’em all. But her secret to getting into shape isn’t limited to just spending hour upon hour doing intense training sessions with her trainer: She also has the keto diet to thank.

Vikander switched to the keto diet two months before filming began, according to PopSugar, and it made a huge difference in her body and in making sure she felt at her best before taking on the badass role.

“Since we were traveling so much over the holidays, we decided the keto diet would be best because it’s easier to control the macros (AKA macronutrients like carbohydrates, protein and fat) that way,” Vikander’s trainer Magnus Lygdback told PopSugar. “It was a high-fat, no-carb diet—not even low-carb. It’s always tricky the first couple of days, but [Alicia’s] willpower is just unbelievable, and she didn’t complain, even though I could see she was struggling a little bit. She kept on bringing it every day.”

Since she wasn’t eating carbs, she was nourishing her body with plenty of other healthy staples: According to Vikander’s trainer, those included a lot of fish and seafood for protein, as well as “MCT oil, avocado, and coconut oil as a fat source.”

Since she couldn’t eat carbs, she nourished her body with plenty of other healthy staples: According to Magnus, those included a lot of fish and seafood for protein as well as “MCT oil, avocado, and coconut oil as a fat source.” In addition, she consumed veggies like it was her job—because, well, it was literally for her job. However, Magnus said to be “careful with overeating too many vegetables because you don’t want to go above 25 grams of carbs a day.”

In the end, Vikander won victoriously with a toned, healthy body to showcase in the #bossbabe-powered film. But, since it’s so easy for the keto diet to awry, make sure you avoid these five mistakes if you try it for yourself.

This is the Swedish cooking rule to making healthy, balanced meals. Or, try the three workout moves model Romee Strijd does after flights.