Cousins Ashaard Wihongi, 21, is 100kg and Zara Kanuta, 22, is 117kg.
The women have started a Facebook page, Big Girls Journey to Weight Loss, to document their experience and say they hope to inspire others.
Miss Te Pana, who aims to lose 80kg, said she wanted overweight people to look at her and what she is doing and believe that they can make the changes in their lives also.
"I'm a big person. This is not easy. It's hard. If I wasn't on this new thing, I'd be at home, sitting watching TV and eating. That's what I've been doing all this time. I was drinking cordial and fizzy - never had water.
"Now I get up, go for a walk, eat a healthy breakfast and then hit the gym. It's good having Zara and Asha there because we push ourselves."
Miss Wihongi, a mother of two, admitted she had been embarrassed to go out walking and training by herself, because of how she looked.
But being able to train with her cousins - and now other women from around town - had made it much easier.
"A lot of big girls are embarrassed of the way they look and that was me. But I just want them to see us and not be embarrassed to go for a walk or the gym. I'm doing this for my kids and for myself. I'm sick of people telling me I'm fat," she said.
The women have already received hundreds of comments and private messages via their page.
The Herald will check in with the girls' progress throughout their journey.
On the web
Follow the trio's efforts at tinyurl.com/nzhweightjourney
