They say it takes 21 days to get into the habit of something.
Well, here goes. I began my exercise habit today (one day down).
3 Good Reasons to Exercise (per Prevention Jan/2011):
you eat less - something to do with signals to the brain to keep you from wanting to eat after exercising.
you get smarter - exercise helps your brain absorb new information, so I guess it depends on what you do while you're running on the treadmill (they should have added a disclaimer: Do not attempt to read and run down the street at the same time)
you get organized - apparently connections in your brain improve to help with strategizing
So exercising your body also exercises your brain - who knew?