"I'd never exercised harder than this for an extended amount of time," Rudd tells PEOPLE of his intense, gymnastics-heavy workouts to become the Marvel superhero.
"My day was centered around fitness and health, and that was kind of a first," he adds. "Every other time, I had to go about my day and try and find the time to work out. But [this time] everything else about my day kind of had to fit in around the workouts. I was going to be held accountable for it, and there was a reason for doing it. I wasn't just randomly doing this kind of arbitrarily, which would have made it a lot harder."
So what was his workout, exactly? Lots of "flips and rolls and all that kind of stuff," he explains, but "I wasn't doing any kind of crazy parkour. You know, I couldn't jump from that roof."
Along with all of the physical exertion, Rudd also took care with what he put into his body.
"I didn't drink any alcohol [and] I had no carbs" for a year, he says. And though the intense regimen was "almost kind of impossible to sustain" – particularly for a guy who has a pub in his basement – Rudd reveals that he's still keeping in shape. "I'm still doing all the workouts, I'm still eating pretty well."
The results are evident, even if Ant-Man was the actor's toughest physical transformation for a role. For This Is 40, for instance, director Judd Apatow "wanted me to be heavier and to eat a lot of cupcakes," Rudd recalls. Sounds like our kind of diet!
For more on Paul Rudd and Ant-Man , pick up the latest issue of PEOPLE, on newsstands Friday