Today he will be up against the likes of Cameron Brown, who has won the event a record 10 times.
Docherty, Brown and other elite athletes attended a fan and media conference in Taupo yesterday, where each athlete was asked about their diet for the race.
Docherty answered he would be consuming Coca-Cola, Krispie biscuits, sugar and gels during the race.
"If you only have sugar and gels during a race, one thing I noticed was the body starts rejecting it."
Docherty said he tried eating Shrewsbury biscuits during the ironman race last year but they were a bit dry and he started coughing them up.
"This year, I'll try Krispie cookies and see how that goes."
Docherty, 36, has been back in Taupo for about a week after returning from his home in California.
He said he would spend the night before the race with his family in Taupo.
"I feel totally at home," he said.
"I will sit down with the family tonight and have pizza, then I'll try to get to bed early, but it will be a restless sleep anyway."
Two-time defending women's champion Meredith Kessler has returned to the event again this year.
The American said she loved racing in Taupo, especially swimming in the lake.
"The lake - it is like one big happy pool," she said.
"I love it here, the culture and community really welcomes you."
If she wins today, it will be the first time she has won three titles in a row at the same ironman event.
"I never take for granted the opportunity to do a three-peat.
"I have the opportunity to try for that here. You have to try and capitalise on that."
Today marks Kessler's 53rd ironman race.
The course comprises a 3.8km swim, 180km cycle and 42km run.
The swim will take place in Lake Taupo, the bike between Taupo and Reporoa and the run will be held along the lakefront near the Taupo township.
This year has a record field of more than 1700 participants from 57 countries, with prize money of $90,000.
The men's and women's winners will take home just under $18,000 each.
Ironman New Zealand was first held in Auckland in 1985 and moved to Taupo in 1999.