When he suggests a venue for explaining his ground-breaking research on the connection between physical activity and brain power in toddlers, it's not his office.

Instead, we meet at a child's playground in the Wollongong Botanic Garden, on the route he takes when he walks to work at the university.

Okely takes his health seriously, running for half an hour each morning and parking his car a 20-minute walk from his office.

The idea that is challenging his university colleagues - as well as office workers - is that it's not just the length of time spent sitting that counts. It's the length of each bout.

Okely argues that if we sit for more 30 minutes at a time, and more than about six hours a day, we put ourselves at risk of a range of health risks, including heart disease and diabetes.

That's regardless of how much exercise we might perform in the remaining hours.

"What seems to be suggested is that when you sit or lie down it suppresses certain enzymes associated with the production of good cholesterol," Okely says.

Since March, he has led a team of researchers at the University of Wollongong to test the connection between activity and brain power in toddlers.

His research teams finished collecting data yesterday from 11 childcare centres throughout the Illawarra to study the relationship between physical movement and brain activity.

Under the guidance of project manager Tamara Raso, around 450 children have strapped a monitor onto their legs that will measure the amount of time they spend sitting, standing and moving over five mornings.

"If any of the children are a bit apprehensive, we call them all sorts of things such as 'power pouches'," Raso said. "We don't want them to run any faster and we just want them to do what they would normally do.

"Because a lot of the centres are quite structured in their routines, we tend to find there is not much of a problem with children over-exercising."

Another researcher will measure each child's height and weight, to assess the relationship between movement and body mass index.

Finally, each child is given three simple mind games - sorting cards, a memory game and a game involving fishes and sharks on a computer screen to test reaction time.

In a few months, Raso and her team will return to each centre with the results and suggestions for how physical activity can be increased.

These may include simple measures such as standing (rather than sitting) for lunch or replacing sitting desks with standing desks. There is some evidence that preschoolers may be sitting for more than half of their day, which could be bad news for the long-term outcomes.

Executive function, essentially how efficiently the brain works, has been shown to be a better predictor for school readiness than IQ and thus the importance of early movement may be difficult to overstate.

"If they are more ready for school, the teachers tend to give them more advanced tasks and the gap just gets bigger and bigger," Okely said.

"They tend to thrive and move on.

"That's been linked to outcomes later in life, such as whether they go to university, their salary level, how well they do in school."

Of particular importance across all ages, says Okely, is vigorous exercise.

"Something happens when you exercise at vigorous intensity," he said.

"It stimulates a part of your brain that helps you with that thinking and concentration."

Phase two of the research, to take place later this year, will involve placing children in a calorimeter - a room at the university the size of a child's bedroom.

This room at the university captures and measures the air they breathe so their exact energy expenditure can be measured.

Some of the factors thought to have fuelled a major increase in childhood obesity from the mid 1980s to the late 1990s (it has stayed high but stable in the last decade) are obvious and unsurprising.

"I think the low price and ready availability of energy-dense and nutrient-poor foods is one factor," Okely said.

"We can get food very cheaply and easily. Healthier options are more expensive and harder to access.

"Whether it's increased taxes on unhealthier foods or making healthier foods more affordable."

The rise of technology and the shrinking backyard are other key factors - children are more likely to play inside - as is the perceived risk of outdoor play, whether from increased traffic or stranger danger.

"The key drivers are the increase in energy intake, a decrease in energy expenditure," he said.

"Parenting skills haven't caught up with that. It's much harder now as a parent to make healthy decisions around eating and physical activity.

"Almost by nature, the environment we lived in 20 or 30 years ago made it easier to make healthy choices where now it's become much more difficult."

But there's more to it than that, which is where Okely's latest research project comes in.

While participation in organised sports has increased, he believes the key factor is the decrease in what he calls "incidental activity".

"What used to happen 20 years ago after school was that you'd drop your bag off go outside and play," he said.

"You were very active and you had a lot of fun.

"My hunch is that incidental movement is highly important and that's what's driving the increases in obesity.

"We make many fewer short trips walking.

"Even if you look at the way our suburbs our organised where the corner store, the school and your friends would all be within walking distance.

"Now you may have to get in your car to make all of those trips."

Okely's hunch is played out by another major research project using 800 children around Illawarra primary schools.

One of Australia's foremost experts on childhood obesity, Dr Jenny O'Dea, has found that active children scored better on literacy and numeracy tests - irrespective of class.

"The children who ate a good nutritious breakfast and who were more active were certainly better academically," O'Dea said.

"Part of it is about nutrition for the brain.

"Part of it is that nutrition and physical activity allows them to sit still and concentrate."

Her academic paper published last year stresses the importance of breakfast and of early morning physical activity, particularly for boys.

The Bulli-based University of Sydney academic has already written a book, Positive Food for Kids, about how parents can encourage their children into a healthy diet.

Her next book may be about the food needed by developing brains.

"Meat is good because it gives zinc and iron; fish is good for fish oils and fatty acids," she said.

"There really are brain foods and it's much better to get them from foods than from supplements because the latest research seems to suggest that the interactions are synergistic.

"That perhaps it's not just the fish oil but it's also something else in the fish.

"You are better off to have a good healthy mixed diet.

"That's always been the case and I think it always will be."

But she cautioned against parents becoming too focused on the merely physical.

"A healthy lifestyle is about physical health but it's also about psychological and emotional health," she said.

"It's about relationships, and it's about spiritual health.

"It's about having a purpose in life.

"Kids needs to develop this and parents often forget that there is more to health than physical activity.

"It's about the whole self, body mind and spirit."