The human body doesn't degrade because of less brain activity, it does so because after you stop growing your cells reproduce in exactly the same way over and over which eventually means they can't regenerate as effectively as before.
As you cells slowly lose the ability to fix the gradual errors that repetitive regeneration brings they begin to die until they can no longer regenerate.
On a celular level this is a very slow proccess, but once it is widespread your organs begin to fail and then you will eventually die when one or more stops working entirely.
Depressing, huh?
It's an interesting hypothesis (and wildly off-topic
) but just because you keep your brain active doesn't mean it will not degrade after you no longer grow (that is, once you lose the inate ability to learn because your brain cells are no longer able to reproduce exponentially).
In fact, my guess would be that if you spent the majority of your life playing games you'd probably waste away much faster as you aren't using most of the muscle groups in your body at all.
Long life is all about variety.
Well that's what I think anyway
------------------
