From 2007 to 2015, he did very little in the way of exercise. He weight began to increase and his cholesterol began to rise.
"All those indicators for heart disease were going up, it was probably a good time to do something about it," the father of four said.
In 2015, he made a deal with himself – if he hadn't gotten into a sport by his birthday he would begin training to compete in an ironman.
A 3.8km swim followed by a 180km cycle, ending in a 42.2km run. It's a long, demanding sport and not one you'd think someone which knee issues would decide to pick up.
But the flexibility and variety of training methods was a large reason as to why he was drawn to it, so he was able to plan his training around work and family.
He competed in his first triathlon in the same year finishing the TriMaori at Lake Karapiro that November. An Olympic-length triathlon, Dewes swam 1.5km, cycled 40km and ran 10km.
"I think I finished that in just under four hours, I didn't die so that was good."
He entered the half distance IronMaori race the year later, finishing in about six hours.
"If you asked me earlier I would have put many thousands of dollars on this not occurring in my lifetime, let alone in 18 months. I was pretty broken at the finish and could hardly move the following day, but it was pretty cool," he said of the race, which was his initial goal in 2015.
But by the time he reached the starting line for that event, he was thinking ahead.
"I was thinking Ironman."
After setting his sights on competing in the 2018 Ironman in Taupo, his schedule became absolutely packed, engaging with a coach to help with the technical side of his training.
Working 55 hours per week as a general manager, which included travelling domestically for two days a week, training during the week would consist of three one-hour high intensity sessions, two during lunchtimes, two one-and-a-half to two-hour recovery sessions.
The recovery sessions would be done in the evenings after his daughters – Atarina, Marirena, Hariata and Raniera – had gone to bed.
Dewes admitted he'd have rather done these sessions before work, but stayed home with the children to allow his wife, Danielle, to go to crossfit in the mornings.
When asked how he ensured training wouldn't interfere with spending time with his family, Dewes was honest and said there was no way around it.
"We just tried to minimise it by doing things when they were asleep and I would try to fit in the longer sessions when travelling. We would always try to be home for after work activities - took them to swimming lessons, martial arts, and my wife took them to crossfit."
During the weekend, training involved four-to-six hours one day, and three-to-four hours on the other. He'd stretch every night, and fit in 30-45 minutes of core work where he could.
In March, he conquered his goal – completing the full ironman race. Understandably, Dewes was "absolutely stoked" with reaching the finish line of the race.
"I am even happier that an unintended consequence includes my daughters wanted to get involved, my wife becoming more committed to exercise and our family eating a little better.
"A couple of my friends and family are inspired by me, have said so, and are doing some positive things with that. I am as stoked about that as I am about finishing."
