Parental shift work and the cost of food are contributing factors to Pacific children's obesity rates in New Zealand, an Auckland University study has found.

Young Pacific people have significantly higher levels of obesity (23.3 per cent) than the general population (8.3 per cent).

Dr Tasileta Teevale led a team of researchers who surveyed 2495 Samoan, Cook Island, Tongan and other Pacific students.

A qualitative phase also interviewed 33 adolescents and 35 parents from 30 Pacific households to further explore the sociocultural factors that promote or prevent obesity.

Published in the New Zealand Medical Journal, the study found that a key difference between obese and healthy-weight adolescents was in parental presence in the home, with parents of healthy adolescents more likely to be home to provide healthy food and monitor eating practices.

Parents in obese households were more likely to be working in shift-type employment - 54 per cent as compared with 8 per cent of households for a healthy weight student.

Shift work also encroached on food preparation time, meaning takeaway meals were the default choice for family evening meals.

The cost of food also reared its head as a determinant of obesity.

One household participant said people knew what were good food choices but it boiled down to cost.

"Usually we will eat white bread. [It's] cheap, it's 89 cents a loaf, I can get two or three ... and then the kids will get full up on that, but I know it's not good for you.

"I'm not going to go out and buy Vogel [brand] everyday cos they are like $5 a loaf ... I do know what to do, but it's just hard on the pocket."

The study said supplementary grants for food purchases could be an option for making a difference, as could removing GST from healthy foods to address perceptions of expense and affordability.

There was also a case for making policy changes to continuous work-time arrangements, particularly in occupations requiring employees to work longer than 10 hours.

"For Pacific families over-represented in low-skilled, low-income shift work occupations, these employment law changes are more pertinent.

"Government policies that support the well-being of families, by ensuring better work-life balance should be prioritised."