As already mentioned, TextWrangler is a pretty good free alternative. I used it and liked it enough to support the team by buying BBedit, which I recommend if you're looking to purchase one.
I find it very similar to the motto I follow when jogging (and also what I"m trying to apply to other things): keeping a steady pace. By keeping a pace, you don't burn out towards later stages.
My entire dev team (all 4 of us) have started doing burpees at 11:00am and 3:00pm everyday. Great all-around excercise that gets your heart racing and even works out the whole body. Japan has a milder version, called Rajio Taiso.
Not sure if I'd be able to walk while in a meeting, even if its at a slow pace. When I'm working out, I usually try to get into "the zone" and I'd probably have difficulties staying focused.
Besides the physical impact, you should definitely look into the mental impact of the craft as well. I've learned (unfortunately through the hard way) that regular exercise (be it yoga, running, etc) helps to relieve stress that our body encounters throughout the day.
In a very similar boat as you. Just went through a very stressful period, resulting in my first ever panic attack, and I think coffee had something to do with it (besides lack of exercise or any sort of stress management). I'm actually scared to drink anything with caffeine now.
Perhaps Digg fixing itself may return some of that Derp back where it came from. I haven't stopped using reddit though, as there are still some great mini communities that are the subreddits.
Going to be honest though, I am an ex-digg user, current reddit user, and just recently started checking out HN on a regular basis for the content and insight I feel has left reddit. Please don't hate me! :)