Mr Mason lost 10kg in the early stages and had to take protein powder with breakfast to maintain strength. The Appalachian Trail is the world's longest continuous footpath and traverses the crest of the Appalachian Mountains which run through 14 states from Georgia to Maine.
Speaking to the Bay of Plenty Times from Manchester in Vermont, where he had stopped for the evening, Mr Mason said he had wanted to do it for a while and decided the time was right while his wife Helen was completing a research project in Boston.
"I've always loved the outdoors and hiking. I can't remember how I found out about it but it's just been on the radar ... It increasingly became a large part of my thoughts. I hadn't really seriously considered doing it, but when Helen went to the States the timing was good for it."
Mr Mason said he started the trail alone but had quickly made "good mates" along the way.
"We're all about the same age. We support each other quite a bit.
"You become very, very good friends. You can be hiking with someone three to four days in a row and you open up quite a lot."
Mr Mason has encountered many challenges. When he started, temperatures at night dropped to -7C or -8C, making it hard to keep warm. "You're out on top of a mountain and it was incredibly cold," he said.
Temperatures now were warmer, but he expected more cold nights during the last 1000km through the infamous White Mountains and Hundred Mile Wilderness, by far the toughest part of the journey. "I've realised I've got far more physical and mental capability than I ever thought I had."