I've never run a full marathon, but I have run a half. My training consisted of maybe a dozen 2 mile runs, and a couple of 6 mile runs, in the space of about a

I've never run a full marathon, but I have run a half. My training consisted of maybe a dozen 2 mile runs, and a couple of 6 mile runs, in the space of about a month. I didn't do any exercise other than that. I wouldn't say I'm naturally athletic either. Sure, I was pretty slow at 2:30, but I managed to run the whole thing without resting or walking. I reckon that I could smash out a marathon with less than 6 months of training, running 3 days a week. It certainly wouldn't take over my life, and it wouldn't take a year of training. A similar endurance event I did once was riding a century (100 miles). Sure, riding a bike is a bit easier than running, but my total training for that was about 6 months, riding 25 miles 4 times a week, plus a single 60 mile ride. I managed to complete the ride in about 5:30. Humans are well adapted to long distance endurance activities. A person of average fitness can walk 12 hours a day for a week with a 15-20 kg pack.