Consequences ... Children as young a 15 are facing the health consequences of inactivity. Picture: Thinkstock Source: Supplied

And researchers are demanding a long term national policy to get children moving to avert the health consequences.

The effects of poor exercise habits can be seen as early as the age of 15 a Sydney University study published in Pediatrics has found.

The long term study of 4,600 children found those who are more active in late childhood have lower body fat and reduced risk factors for cardiovascular disease.

Healthy kids ... Children who are active have lower body fat and reduced risk factors for Type 2 diabetes and cardiovascular disease. Picture: ThinkStock Source: Supplied

The good news is an increase of 60 minutes of daily activity in childhood was linked to two per cent less body fat, the study found.

Motion sensors were used to measure children’s physical activity levels at 11 years of age, which was compared to their health outcomes at 15 years of age.

Lead researcher Associate Professor Emmanuel Stamatakis from the University’s Charles Perkins Centre says just one in five Australian children move enough to meet the national guidelines of 60 minutes moderate to vigorous activity a day.

And 70 per cent exceed the recommendation they spend less than two hours a day engaged in front of a screen.

In the study the children spent an average of just 25-30 minutes doing such activities which include walking, cycling, playing and taking start in sport.

They spent just 5-7 minutes a day in vigours sporting activities.

Not good ... Only one in five Australian children do the recommended 60 minutes exercise a day. Picture Thinkstock Source: Supplied

Getting children moving is a job that can’t be left to parents alone, he says.

A national strategy is needed to combat the problem and prevent the long term consequences of inactivity, he said.

“With technology today meaning excessive sitting and screen time, we urgently need a serious long-term health policy which promotes strategies in schools and communities to give young people more opportunities for walking, cycling, play, and sports on a daily basis,” he said.

“If inactivity patterns persist into adulthood, which is very likely, we expect an increased risk for developing heart disease, diabetes, and obesity.”

Professor Stamatakis says we need to make it easy for children to be active.

Schools should be turned into car free zones to encourage children to walk to school and walking buses should be promoted to get kids to school.

Changes needed ... We need to make exercise the easy option for kids says Professor Stamatakis. Picture: News Corp. Source: News Limited

Cycle paths need to be improved around schools, he said.

A side benefit of the extra activity would be fewer cars on the road, he said.

The study provided clear evidence that the negative effects of inactivity in childhood are evident well before adulthood, he said.

The research is the longest running study to objectively measure children’s physical activity and sedentary behaviour against measures relating to heart health, obesity, and diabetes.

The study did not show any association between sitting time and negative health consequences; however the researchers speculate that a longer-term follow up into adulthood could reveal different results.