Fixx was a very good writer (by that I mean his books were fun to read), and much of what he wrote was true. I never read "Games for the super-intelligent", but from what you describe, as he did in the Complete Book of Running, he wrote what he wished to be true. He outlived his father, and I believe, extended his life by running. Unfortunately, from the accounts I read of his death, he had several classic symptoms of insufficient blood to his heart, and ignored them. He refused to see a doctor, and insisted that running would cure him. I remember reading the article about how his body was found, and he was out running alone when he had his heart attack.
I felt very betrayed when I read of his death, as I started reading his books at that time of youth when you're looking for something to define yourself as a human. I fell totally into running, and actually owe Mr. Fixx a lot. When I think of some of the other things I could have gotten into at that fragile time of life, it gets pretty scary.
So I'll always have a soft spot for old Jim. In a very real way, he saved me. I was searching for something so badly then, and like most kids, I had no idea what. Spending a few years running, as opposed to running drugs, wasn't a bad way to waste part of my youth. I think I'll pull out the old jogging shoes tomorrow and slog a couple of miles. A fifty year old man sluffing along isn't nearly as impressive a 19 year old running like a gazelle, but I'll take it easy and pretend people aren't laughing at me.
I wasn't a disciple and I was already on the varsity track and cross country teams by the time I got any of his writings on running, but I will always remember the Jim Fixx runner's diary which I used diligently to record all my practice, race times, weight, etc. etc. every day. I still have it around somewhere for nostalgia, though as an old man I can only look in wonder at what I used to be able to do every day in high school.
Do it. I'm 46 and started back in August after years of slugdom. You'll feel great after 6 months or so of agony.