Thinking makes you fat.
It turns out that performing mental tasks, like trying to solve problems while working at a computer, stimulates the appetite so much that people tend to eat significantly more calories than they burned while performing the "knowledge-based" tasks.
You know what else makes you fat? Blogging. NOM NOM, bitches, NOM NOM!
Does Thinking Make Us Fatter? [abcnews]
Thanks to barney, living proof that being dead sexy makes you skinny.