Programs designed to increase physical activity of children have failed to get kids moving. This is clearly not enough to fight rising obesity rates, new research finds.

Researchers from Plymouth University looked at 30 studies that took place between 1990 and 2012, each lasting for at least four weeks, which monitered the bodily movements of children under 16.

The study, which looked at the effects of extra exercise sessions, showed that attending exercise sessions was only equivalent to doing an extra four minutes of running or walking per day.

Extra sessions were only enough to show "small to negligible" increases in children's total activity, the study found. This would have minimal impact on children's body mass index, or body fat.

"It could be that the intervention specific exercise sessions may simply be replacing periods of equally intense activity," the study found. "For example, after-school activity clubs may simply replace a period of time that children usually spend playing outdoors or replace a time later in the day/week when the child would usually be active."

A P.E. class can often lack energy, involving 10 minutes of running, 10 minutes of walking and 20 minutes of standing in a line waiting for your turn, Brad Metcalf, a medical statistician from the department of endocrinology and metabolism at Plymouth University and lead author of the study, told BBC News.

Parents may opt for a less active activity or allow more snacking, under the assumption that their children have already had their exercise for the day, BBC reported.

"We know physical activity is important. What we're not good at is designing behavioral interventions that increase it," said Mark Hamer, a researcher at University College London who wrote an editorial accompanying the study.

Though disappointing, the results are no reason to become discouraged in our efforts to get kids moving, Hamer said.

Rachel Lowry is a reporter intern for the Deseret News. She has lived in London and is an English graduate from Brigham Young University. Contact her at rachel.lowry@gmail.com or visit www.rachellowry.blogspot.com.