Or take Swordfish, in which Hugh Jackman plays the world's greatest hacker while having the exact same body type as when he plays Wolverine.
Warner Bros. Pictures
Sure, being a nerd doesn't make it impossible to work out, but nothing about these characters suggests that they've ever been to a gym, let alone spent half their waking hours there. The real John Nash looked like he couldn't risk going outside whenever the wind picked up, but Crowe portrayed him as if math was the subject he was only pretending to study until he was selected in the NFL draft.
This is clearly because the actors have to maintain the kind of atypical bodies that Hollywood demands from its stars, but these days, even actors who don't generally do action have to be ripped, no matter how much it clashes with their characters. Chidi from The Good Place is almost entirely built around indecision and fear of commitment, yet look at him. So the one thing he could commit to was an extensive daily workout routine?