You need three things to get you through a marathon:
1) Cardiovascular and muscular fitness. Believe it or not, this is the easy one. If you follow a good training plan, you *will* develop the fitness necessary to get you through the race.
2) Mental toughness. This one is up to you. Getting through your training means a huge time commitment. Are you going to find the time every single week? Are you going to make the sacrifices? The other side of mental toughness is running through mild discomfort. Some days running will feel great. Other days it's going to be a challenge. Now, to be clear, *pain* is bad; you almost never want to run through pain. But discomfort is going to be there many days. Are you going to quit or "suck it up and deal?"
3) Structural strength: This is the tough one. Unlike muscular fitness - which will come if you train - your joints, bones and tendons can take a lot longer to strengthen. I wish I could tell you that, "yes, absolutely, you can do the 2008 marathon." But your body may hold you back a bit.
For most people, it is very possible to go from couch potato to marathoner in 6 months. They won't run the fastest marathon after only 6 months and may have to mix in some walking, but they can get through 26.2 miles.
But they can have a lot of trouble at the start. They will be super-motivated, their muscles will quickly be willing to go, go, go. But their structure can still be weak. They really have to hold back at the start to avoid injuries. Which can drive you bonkers.
The great news for you is twofold. If you can walk through 3-4 miles, that shows a good foundation for structural strength. And you don't want to run a marathon in 6 months, you want to run one in 15 months. That gives you a ton of time.
Obviously you want to see a doctor and maybe a trainer before starting. But here's what a reasonable plan might look like:
Don't even think about marathoning for a couple months. Start slowly with a big variety of different workouts. Walk a couple days a week, mixing in other exercises on other days. Build slowly. Don't get injured. If everything is going great, start to work in a little jogging during your walks.
After a couple months, how to you feel? You'll probably feel so good you'll want to start thinking about marathon training. Instead of shooting for a 2008 marathon, you can start thinking about mid-2007. Or maybe you'll be having small problems with minor aches and pains. Then you keep going with more base building for a few more months before starting a formal marathon plan.
There are no promises; there are no guarantees. However, it is extremely likely that you will be able to start training and complete a marathon by Jan. 2008.
Well, I take that back. Here is one guarantee. If you start towards this goal today and keep at it
. If you get out and get active, you will feel so much better - both physically and mentally. It's be one of the greatest things you'll ever do for yourself.
: Your post was informative/honest/motivating all at the same time and I really appreciate it. I think I could do this and I know I WANT to do it. I know in my bones that there's a runner in me - weird huh? I just know it -When I see runners I know it's what I want to be doing to push myself that way and to be able to say I'm a RUNNER. Thank you so much for your thoughtful post I really appreciate it. 
