Playing video games makes you thicker.
And that's a good thing.
A study study shows that there is a strong correlation (not actually a causal link, yet) between heavy video game use and "cortical thickness" - a neuroscience term meaning greater density in specific brain areas.
Researchers studied the brains of 152 adolescents, both male and female, who averaged about 12.6 hours of video gaming a week. The findings are potentially surprising and important, though many have made the argument before that gaming improves your brain rather than weakens it. (See Stephen Johnson's 'Everything Bad Is Good For You').
Anyway, this is just another reason to go play Mario Kart. Get to it, brain athletes!