She has lost 16kg in the last 18 months and this will make the run easier than it would have been when she started running four years ago.
Haig (46), a radiation therapist at the cancer ward of Dunedin Hospital, is naturally a bit apprehensive about facing the 61.2km mountain run.
"It's the biggest thing I've ever done in my life," she said.
That includes a 10-hour hike to the Everest Base Camp.
Haig likes to challenge herself and that is why she started running 30 minutes a day in 2005She hated exercise when forced to run around the block when she was a pupil at Columba College.
"I hid in a garage until the keen girls came back," she said.
"I tried to avoid sport at all costs."
Running was difficult for Haig because she weighed 78kg when she started.
It became easier as she started shedding weight.
Her friend Libby Reid, a nurse at student health, provided the impetus for the weight loss when she persuaded Haig to be a guinea pig in a study run by the Human Nutrition Department at the University of Otago.
Haig's group ate a high protein diet and the other group was on high fibre food.
"I lost 6kg in two months, kept the diet going, and lost another 10kg," Haig said.
The diet was low in carbohydrates like bread.
The main ingredients were tuna, lean meat, chicken, fish and a lot of vegetables.
"I had problems with my calf muscles when I first ran," Haig said.
"It is easier on my joints now that I carry less weight."
Haig's weight has stabilised at 62kg and she is now able to handle a six-hour training run with ease.
"After a four- to six-hour run at the weekend I give myself some chocolate as a reward," Haig said.
Haig's training consists of three runs each week - 1hr 30min on Tuesday, 2hr on Thursday and four to six hours at the weekend.
She has a long run over Swampy Summit, runs the Waitati circuit and has become familiar with the Kepler Challenge at Te Anau with a six-hour run.
Haig, and her partner Grant Taylor, have a holiday home in Ophir in Central Otago and run on the Rail Trail, and through Thompsons Gorge from Omakau to Tarras.
She also spends two days lifting weights at the World Gym and has had a monthly therapeutic massage by Rose Martin for the last decade.
Haig runs for her health and for personal achievements.
She does not expect to be a champion athlete.
She will run her first Kepler Challenge on Saturday.
Her best times in other events are: Luxmore Grunt (27km) 4hr 36min, Auckland marathon (5hr 05min), Motatapu mountain marathon (5hr 56min).
Her target time for the Kepler Challenge is between 10 and 11 hours.
At a glance
Date: Saturday, December 5
Distance: 61.2km
First held: 1988
Runners: 400
Race records: Men, Phil Costley, 4hr 37min 41sec, 2005.
Women, Zelah Morrall, 5hr 23min 34sec, 2003.
2008 results:
Men, Martin Lukes 4hr 56min 24sec, 1; Sam Wreford 5hr 03min 04sec, 2; Tony Fattorini 5hr 06min 50sec, 3.
Women, Chigaya Mase 6hr 06min 20sec, 1; Eveline Coombe 6hr 20min 51sec, 2; Jean Beaumont 6hr 22min 34sec, 3.
