Mental workouts?

LKinnos

I've been wondering...

I study advanced Japanese. And after yesterdays 7 hour session of translating listening interviews, ploughing through articles and getting my tongue around difficult grammar structures, I felt like I'd run a marathon... and I was starving!

I've started exercising again purely because I am sitting and studying for most of my day... but am seriously wondering the energy input for mentally stretching and twisting my brain for extended periods of time.

Ive stumbled on this article which is interesting... http://www.saga.co.uk/health/healthy-Eating/tailor-made-nutrition-to-suit-your-day.aspx

Does anyone know anything about this? Ever studied something truly difficult and wondered the same thing?