system
Given the following post, respond as if you're commenting on Reddit:
human
[Death Note] How Is L So Strong When He Sits In Front Of A Screen And Eats Sugary Foods All Day?

So we know that L doesn't really get out a lot judging by his posture and the darkness under his eyes. And we clearly see him eat sweets and Watari even serving ice cream to him and the police force. Plus with all the cases he has solved you don't think there would be much time for working out. So how was he able to contend with Light and even take a point blank punch in the face without flinching in their scrap?
gpt
I think you've got a false premise about L's fitness. By all accounts, he's in good shape. 

He was a tennis champion in England and played a strong match against also-champion Light.  He knows capoeira and probably practices regularly, which is a good workout itself, and could have easily trained him to take a punch. Also, I'd be surprised if Wammy's House didn't instill the value of a workout regimen in its graduates.