Among those he came across were Ava and Perrin, sisters who had taken to licking the inside of their peanut butter bag to get sustenance on the trail; a hiker known as "Blackhawk" from Dallas, who spent just one night outdoors as a kid; and Cesar, a paramedic from Denver who thought about spirituality out on the trail.
Fanning spoke with Colorado Matters host Ryan Warner. Click the audio player above to hear their conversation and read highlights below.
On why he chose the Colorado Trail:
"I had done a hike through Colorado in 1981. My wife and I had hiked the length of Colorado along the Continental [Divide] Trail. This was in the days that there was no trail there -- we had just pieced together a trail. And I had gotten into the San Juans and I always said to myself, 'I am going to go back there.'
"Two years ago, we had a medical emergency. My wife and I had four days to think about how our lives might seriously change while the lab reports were coming back. We had this discussion about what we were going to do. Carol is a biology teacher; she wants to go to the Galapagos Islands -- we are going there this summer.
"I wanted to get back into the San Juans because I promised myself I'd be back there. So I decided to hike the Colorado Trail to get back there. It was a spur-of-the-moment thing. I just picked up a pack, grabbed some food and off I went. ...
"Carol is great. It turns out we got good news from the doctor -- unexpectedly good news. But now we can live our lives in a different way. We can fulfill those promises."
On why he decided to gather stories:
"In 2014, I hiked the trail by myself. But I ran into two other people to hike with, solo hikers -- a 34-year-old women and a 19-year-old kid. I'm 63. The three of us were the most unlikely group of people to hike together, but we had such a good time. I said, 'This trail is absolutely terrific.' It was the best hiking experience of my life. So I said, 'I want to do this again, but I want to interview hikers for a book. I'd like to write a book about the Colorado Trail.' So I decided to hike it in the opposite direction, from Durango to Denver."
On 'trail angels:'
"There's a real community on the trail. And a lot of times, the mountain folk in those trail communities will do nice things for hikers, if for no other reason than they wish to be helpful. ... They will set out a cooler that will be full of drinks ... Gatorade, beer -- I've had beer on the trail."
On what he thought about on the trail:
"For me, one of the most beneficial aspects of doing a long hike is the not thinking. You just walk. You get to the end of the day, and you sit down on a log and start to get your dinner ready and you think, 'What did I think about today?' And the answer is always the same: not one darn thing. I just walked. I just put one foot in front of the other. There's something that is space clearing. It clears out a space for you to solve some of the issues that you are dealing with in your life. ...
"Hiking changes you in unexpected ways. It really makes living the rest of your life different in a very real way."