After her dad died McCullagh has worked hard to get healthier. She now exercises five times a week and has lost significant weight.
"At 5 foot 3 (160cm) I weighed 64kg and although I was never large, I also wasn't healthy. I was lucky if I exercised more than a couple of times a week and I often ate whatever I liked.
"Six months following dad's death I decided I wanted to exercise regularly and be 'healthy'. I joined a gym, cut down eating rubbish and I now weigh 55kg and on average would exercise five times a week. For me losing weight wasn't to look good but rather to improve my overall health and wellbeing."
She has chosen the Heart Foundation as her charity because she has witnessed firsthand the impact heart disease can have on a family.
"I am determined to do a half marathon and prove to myself that I can do this, for myself, my dad and for the New Zealand Heart Foundation.
"This is a charity that for me couldn't get closer to home and I would love to raise money for this great cause."
The family of Herne Bay man Richard Davidson has been hit hard by heart issues.
His great-grandfather had a fatal heart attack over 25 years ago. His father needed a valve replacement about 10 years ago due to a birth defect, and his grandfather had bypass surgery five years ago after having a heart attack.
"Many New Zealand families have long histories of heart disease, and my family is one of these," he said.
"If anyone should be thankful to the Heart Foundation for their research into heart disease and on-going initiatives to encourage Kiwis to live healthier lives, I should be.
"I am running the marathon partly to raise money for the Heart Foundation, whose research has directly impacted my life through treatment of family members, and partly to get myself fitter than ever before and get my heart into top condition."
Davidson has two goals for the event; to raise $2000 for the Heart Foundation and secondly to run his first full marathon in less than three hours.
"Both are going to be difficult, but are totally do-able."
He has been training hard since early July, running five to six mornings a week and at least 100km per week.
He wants people to support him and The Heart Foundation on his page.
"I am sure the last 10km of the marathon will be a hard place - to know I have people behind me will make a huge difference."
Terry Elliot's 3-year-old son Max was diagnosed with a heart disease in January this year.
He has hypertrophic cardiomyopathy (HCM). It's relatively rare to have this disease at such a young age. Max had open heart surgery on April 2 to remove excess tissue causing an obstruction to the outflow tract on his left ventricle.
The surgery was a success and with medication and good management Max should have a long life - albeit with some restrictions.
"The fact that Max was diagnosed at such a young age is a blessing as we are now aware of the situation and can minimise risk of any event," said Elliot.
"With all the good work and research that the Heart Foundation does, hopefully one day there will be a cure for HCM."
Each day 16 New Zealanders die as a result of coronary heart disease - one person every 90 minutes. And many of these deaths are premature and preventable.
Elliot is running the marathon and has signed up as a Heart Racer to raise money to support the Heart Foundation.
"I am asking people to help me as I join the race to beat heart disease," he said.
"I'll do all the hard work [train for and complete the event], but I really need you to make a difference to the hearts of New Zealanders."
Matthew Jeromson is running the half marathon to raise money for the NZ Breast Cancer Foundation.
He was inspired to run by his employer, Iona Matheson, who owned a mushroom business at Hunua with her husband Phil.
Iona died just a few weeks ago after Matthew had signed up to run. She had outlived doctors' expectations with her stage 4 breast cancer.
"I can't imagine what Phil and the kids are going through," said Jeromson, a 20-year-old student.
"I was so shocked and sad to hear of Iona's passing. I honestly thought if anyone was going to beat cancer it would be her. Knowing someone who was killed by the disease makes this whole thing so much more personal."
Jeromson, who is aiming to raise $2500 for the NZBCF, has never been a runner and never done a half marathon before but he is not lacking in motivation.
"Iona was hugely inspirational, she was a battler no matter what illness was thrown at her, so strong and just all round amazing.
"The rest of her family, Phil, Ivanna and Lachlan are also really inspirational, they have gone through everything and come out just as strong, it really keeps me going."
Justine Smyth is also leading by example. The chairman of the NZBCF Board of Trustees is running the half marathon and has already made a huge difference.
"I am very proud to have raised over $10,100 for NZBCF and be the top fundraiser for the Auckland Marathon event," she said.
More than 16,500 participants will take part across all events and it is anticipated that $750,000 will be raised for charity by the participants.