A University of Otago study has found the effect of school canteen food on whether a child eats healthy food is relatively small.
Researchers found that children eat more unhealthy food on non-school days, and are twice as likely to eat hot chips.
Co-author Winsome Parnell says it is naive to think that the childhood obesity problem can be solved by banning junk food at schools.
She says parents need to take more responsibility for their children's health, as only one third of a child's energy intake happens at school.
