In May of 2014, a man set out, walking down a trail from Springer Mountain in Georgia's Chattahoochee-Oconee National Forest. He kept walking for the next 153 days until he reached the top of Maine's Mount Katahdin. The man, known on the trail as "Green Giant" and in the real world as just Gary Sizer snapped a couple of pictures before he left on his long walk and then again when he was done. The effects of the hike, seen in his photos above and below, are pretty stark.

Before and after hiking the Appalacian Trail.

Sizer hiked along, of course, the Appalachian Trail, a stretch of hiking paths that runs more than 2,000 miles from end to end. Millions of people hike the AT every year with a few thousand setting off to conquer the entire length in one go. (My two friends Brian and Leon hiked it a few years ago and produced a great documentary of their adventures.)

Forest trail.

Sizer's goals were more literary, and he wrote a book called "Where's the Next Shelter?" about his time on the trail. The book is based the blog he maintained while hiking that's chock full of stories and photographs from his five months of walking. Swing over and check out the rest of his words and images, or pick up a copy of the book.

After he finished his 153-day hike, Sizer returned to the software company he was working for, but after he got back, "it didn't work," he said in a Reddit AMA in 2017, and he quit. Now, Sizer teaches at REI and sits on the board of the Appalachian Long Distance Hikers Association as a member-at-large. "One might even say I'm obsessed with the outdoors," he said.

Meanwhile, if you're feeling inspired to start hiking the AT yourself, here's a picture from Sizer via his 2014 AMA to get you in the right frame of mind.

Appalachian Trai

This story was originally published in October 2014 and has been updated with new information.

Shea Gunther ( @sheagunther ) is a podcaster, writer, and entrepreneur living in Portland, Maine. He hosts the popular podcast "Marijuana Today Daily" and was a founder of Renewable Choice Energy, the country's leading provider of wind credits and Green Options. He plays a lot of ultimate frisbee and loves bad jokes.