After decades of rising child obesity rates, New Zealand may have finally turned a corner - at least when it comes to preschoolers. In part two of a five-part series on children's health, the Herald looks at tentative gains in tackling obesity - including a promising discovery about children's sleep patterns.
People who work in childhood obesity in New Zealand are used to relentless, bleak statistics.
When Kiwi kids start school, a third of them are overweight or obese. Those rates have been rising for decades, and carry on into adulthood, leading to chronic health conditions and stretching the public health system.
But researchers poring over data recently had a minor cause for celebration.
"Around 2010 there was a change," said Professor Wayne Cutfield, paediatric endocrinologist from Auckland Hospital and the University of Auckland's Liggins Institute.
"That increase in childhood obesity has now plateaued and slightly dipped over the last eight to 10 years.
"It has occurred across all ethnicities, and that includes Māori and Pasifika. It has occurred across the affluence divide. And it has occurred across the country."
The change was unique to New Zealand.
"Our rates of obesity are still high," said Cutfield. "But this change in behaviour, which is the most promising and exciting thing, hasn't been reported before across a whole country.
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"There have been reports in little pockets of a country, like in a city or a town or a certain ethnic group, in the US and the UK and Australia, but not across an entire country like this, not across the affluence divide, not across all ethnicities."
No one yet knows why it happened. But researchers have begun their detective work.
They know the rate of overweight mothers has not fallen, so the change must be occurring after birth. There are some initial areas of interest. More New Zealand kids are going to early childhood centres, where they are more likely to get healthy meals or get an intervention if they are gaining weight. Changes in television advertising about junkfood could also be a factor.
The trend was limited to preschoolers, and obesity rates are still rising among New Zealand schoolkids. Around 101,000 children, or 12 per cent, of children aged 2 to 14 are obese - up from 8 per cent 10 years ago.
But in an area which has long been an embarrassment for New Zealand, the change in obesity rates has generated some optimism in an often-disheartening field. And because it is occurring at the early stages of life, it could have a ripple effect through to school-age children and adults.
If researchers can pinpoint what led to the falling obesity rate among preschoolers, it could possibly be replicated at other age-groups.
Poverty, not culture, the main factor
It is often assumed that cultural factors have the biggest influence on New Zealand's child obesity rates, because prevalence is higher in Maori and Pacific communities.
But the biggest single factor in obesity rates is deprivation. If poverty levels were removed from the equation, obesity rates between all ethnicities in New Zealand would be similar .
Families on low incomes are less likely to be able to afford fruit and vegetables, more likely to purchase fast food, and more likely to watch a lot of television. They generally have less time and less structured lives which makes it harder to have healthy habits or provide nutritious meals for their children.
This means that child obesity rates are unlikely to fall significantly in New Zealand until poverty levels are reduced - something the Government is trying to address through its child poverty targets.
While deprivation is the single most important factor, there are promising fields of research and regional initiatives which could contribute to lowering New Zealand's obesity rates.
'Sick to death of nutrition messages'
One of the newest areas of interest is whether kids are getting enough sleep. It is already well known that poor sleeping patterns in childhood are a risk factor for obesity.
"It's surprisingly consistent," said Professor Rachael Taylor, deputy head of the University of Otago's Department of Medicine and a childhood obesity expert.
"If we tried to look at physical activity or diet in relation to obesity, even though we know they're important, the research isn't nearly as consistent. Virtually every study finds a relationship between sleep and obesity."
With this in mind, New Zealand researchers looked at whether a brief "sleep intervention" in the early stages of a child's life could reduce their chance of becoming obese.
A group of parents in Dunedin had a consultation with a nurse late in the mother's pregnancy, again when the baby was 3 weeks old and, if necessary, another one at 6 months old. They were given advice about managing their child's sleep, which mostly focused on helping the baby to self-settle.
"We actually all wake up in the night, every night, lots," said Taylor. "But if the baby can go back to sleep by themselves, their sleep is probably better, and so is yours."
The results were very promising. When researchers checked in with the children at 2 years old, their risk of obesity was halved compared to children who did not get the intervention. The results were also persistent. At 5 years old, the risk was still halved.
The study has some limitations, not least because it took place in a city where the population is predominantly white and middle class. And the intervention, which includes a recommendation that kids sleep in their own bedroom, can be lost on poorer families who are more likely to be in crowded houses or have more chaotic lives.
But the study is exciting for a number of reasons. Because the intervention is simple and brief, it could potentially be scaled up nationwide by including it in the free Well Child or Plunket check-ups which are already available to parents.
The other benefit of focusing on sleep is that it is not as stigmatised as eating or exercising. If the Government or health sector tries to tell families how to eat or to get off the couch it can be called intrusive or "nanny state".
"I see sleep as a stealth mechanism," said Taylor. "I think parents and the public are sick to death .. of nutrition messages and perhaps physical activity messages to a lesser extent.
"Sleep is a much more novel, potentially interesting field which parents are extremely receptive to."
'Sugar tax needs to stay on the table'
The other side of reducing child obesity is prevention, which is mainly about creating an environment which does not encourage excessive or unhealthy eating habits.
This has proven harder to address in New Zealand, partly because of an influential food and drink lobby and political sensitivities around telling families what they should and should not eat.
Yvonne Anderson, a paediatrician at the University of Auckland's Liggins Institute, said Kiwi kids were living in an obesity-promoting environment in which unhealthy food and drink was readily available, cheap, and heavily promoted.
"At the moment, parents are having to actively work against this environment on a daily basis when they are trying to make healthy lifestyle choices for their children.
"If the healthy choice isn't the easy choice when they're going out into the community ... then it's very hard to make those healthy lifestyle choices persistent."
There has been some progress. The Ministry of Health's National Health Survey shows fizzy drink consumption has fallen in the last 10 years. However, at the same time, fast food consumption is rising.
"There are a few good signs," Anderson said. "But we need to move faster and see more significant change in terms of reducing this obesity-promoting environment.
"There is no one silver bullet. But a sugar tax needs to stay on the table."
• Monday: Vision and hearing
• Today: Child obesity
• Tomorrow: Breathing problems
• Thursday: Behavioural problems
• Friday: Immunisation