I have no problems if its school related, i think of school more as work than for fun. But for me reading and walking at the same time doesn't work for me, i get incredibly lazy if i want to read for fun compared to playing video games because my eyes are glued to the screen and you can just save and pause the game. With books its like a determination that you have to read so and so many pages before you can do anything else.
I just can't deal with being a bookworm and being active, its purely impossible for me. So how do bookworms manage to be in shape while reading for fun? That takes some massive skill.