Kiwi kids' bedrooms will become research labs in a world-first study exploring the complex link between poor sleep and bad eating.
Research has suggested that sleep loss, while not a direct cause of weight gain, can set up the right conditions for poor eating among children – especially when energy-dense foods are close at hand.
But the reasons why were much less clear.
A new project, being led by Otago University researchers Associate Professor Barbara Galland and Professor Rachael Taylor, built off what we knew from the few studies done to date.
They'd indicated that even just a few hours of sleep over one to five nights could increase energy intake by 7 to 21 per cent.
Given the damaging health impacts of childhood obesity - and the knock-on risk that created for later life – the researchers felt it was critical to take a deeper look.
Specifically, they wanted to know if poor sleep increased eating even when a child's stomach was full, if there were any changes in when, where and how much they ate, and if it led to weight gain and more time sitting down.
While most studies in adults had been conducted in carefully controlled experiments in sleep labs over several days, it wasn't so straightforward when it came to kids.
"Because of ethical constraints, we can not simply take children out of their home for a week to mimic the adult lab studies, control sleep schedules, and investigate how food intake might change when sleep-deprived," Galland said.
"Instead, and with the help of parents, we will turn children's bedrooms into 'pseudo sleep laboratories' by night, and apply carefully considered sleep and wake times to manipulate children's sleep for both sleep loss and gain."
The children would be monitored using a sleep watch with a motion sensor that could tell when they were awake and how active they were.
After a week, the researchers would have enough information to know how they normally slept.
"Back in the lab, we take the information from the watch to work out what their normal sleep and wake times are," Taylor said.
"We use this information to then ask them to either restrict their sleep by going to bed one hour later than their normal for a week, but wake at the same time, or extend their sleep for a week."
The children would then be given a week off to get their sleep patterns back to normal, before switching to the alternate regime for another week.
"This crossover in the design means each child acts as his or her own control in the experiment to compare differences in what and how much they eat between the restricted and extended sleep conditions," Galland said.
Throughout the study, the children would come into the lab for feeding experiments.
"Here they get offered treat foods after eating full meal, to see if the amount they eat differs between the restricted and extended sleep conditions," Taylor said.
"We also have them participate in a computerised task where they rate their desire for many different food types.
"We also find out where, how much, and what they eat going about their normal daily lives by having them wear wearable cameras over two days of each experimental week."
It was hoped the study – the largest of its kind in the world, and supported by a Marsden Fund grant – would ultimately help inform sleep guidelines for children.
Most of the sleep recommendations for children were built around how much sleep children need to behave well and perform to their best in the classroom.
"However, we know that many children worldwide get less than the recommended amounts- and New Zealand children are no exception," Galland said.
"If we can build the evidence towards knowing how much sleep children need for healthy eating – then that will give parents, educators, health professionals and policymakers something tangible to work with.
"Showing exactly how poor sleep may promote unhealthy eating and ultimately weight gain, has huge benefits for additional health advice around obesity prevention that currently has a main focus on nutrition and exercise."