One in three New Zealand children is overweight or obese when they start school, research team co-leader Prof Rachael Taylor says.

The parents of half the 800 babies in the Otago study took part in a short prenatal discussion on sleep and received some further follow-up support.

The “striking” finding of the Otago study is that those infants who received sleep support were half as likely to be obese by the age of 2 than those who had not received it.

The “amazing thing” was that these weight-related benefits were just as strong at 5 years of age, “despite no intervention having had occurred for three years”, Prof Taylor said, Science Daily reported.

“I think sleep offers us a really exciting, different way to approach weight, that has benefits for so many,” she said.

Prof Taylor, who is director of the Edgar Diabetes and Obesity Research Centre, said every parent knew “getting enough good quality sleep keeps a child happy, behaving well and enjoying life”.

“It also helps them do well at school, their diets are better, and they tend to be more active – all factors that help us be healthy.”

It is understood that the Otago study provides some of the clearest international evidence of the value of a brief sleep-related intervention in reducing early childhood obesity.

The study was published in The American Journal of Clinical Nutrition, and funded by New Zealand’s Health Research Council.

Dunedin School of Medicine dean, and study co-lead Prof Barry Taylor said the long-term benefits shown in the study, despite no ongoing contact, were “almost unheard of” for obesity interventions.

Prof Taylor also runs a special clinic for very overweight children and says it is important for children to have a regular sleep routine.

Children should go to bed at a time that gave them enough sleep so they were not tired the next day, and screen-time should be avoided for at least 30 minutes before going to bed, as well as in bed.

Prof Rachael Taylor said those families receiving sleep support were also visited when the infants were about 3 weeks old, and researchers discussed with parents how to help their child with sleep.

If a sleep problem developed, expert support was available until infants were 2 years old, and about 100 parents took up this support, she said.