Increasing sedentariness among children around the world makes fighting the problem of childhood obesity even more challenging than ever.

In the United States alone, more than 12 million children between the ages of 2 and 19 years are obese — one out of every six children, cite the Centers for Disease Control and Prevention.

Nearly one-fourth of children entering primary school in the U.K. are obese or overweight — by the time they leave at the age of 11, the numbers increase to around one-third, comparable to the United States percentagewise.

Along with healthier eating, promoting physical activity has been long considered a cornerstone of obesity prevention and treatment. But how much impact do exercise and sports have on this critical global issue?

Kids in Britain ask for more dodgeball

A new report published in July by Office Standards in Education, a regulatory body in the United Kingdom, states that schools are not equipped to take on the responsibility of solving the obesity problem given the broad nature of the issue that encompasses factors outside the control of educators and the school system.

However, schools are being called upon to address whatever falls into the realm of education. Physical education is a key area where investigators say schools can make a difference. In fact, parents are calling for more PE and physical activity in schools as many find after-school club activities inaccessible economically and logistically.

Despite claims from schools that don’t have the standard two hours per week of PE that other physical activities are offered daily, only one-third of the students interviewed agreed with that claim. Interestingly, they aren’t pining for expensive sports that require special equipment such as cycling or facilities like swimming. Many just want to play more dodgeball.

Team sports cut down overweight risk for teens

While links between physical education and lower rates of overweight children exist for the primary grades, gym class showed no impact on weight status in a study of 1,718 ninth- and 10th-graders from 26 randomly selected New Hampshire and Vermont high schools.

Instead, the results of the survey-based study lead by Keith Drake of Dartmouth College revealed that playing more than one team sport per year cut risk of overweight or obesity by 22 percent compared to no participation. Walking or cycling to school was effective in reducing obesity.

"High school sports participation typically involves regular practices and competitions, leading to consistent moderate to strenuous activity, which may explain the strength of its relationship with weight status compared with other forms of physical activity," wrote Drake's group.

Sports programs may not fulfill promise of obesity prevention

Youth sports programs are not designed to prevent obesity, yet they are seen by many as a promising alternative for obesity prevention due to the high levels of regular physical activity required.

Still, little research has focused on sports settings compared with schools and after-school programs, claim authors of a 2011 research review out of the University of Minnesota that examined 19 studies comparing youth sport participants and non-participants on weight status, diet and physical exercise.

They found no clear pattern of association between sports participation and body weight.

For example, among the studies with more than 1,000 study subjects. 24 comparisons were examined and only nine of these showed significantly lower weight status among sport participants. In the majority of the studies, authors note that it isn’t clear whether sport is causing the participants to be more active or whether children inclined to be active join such programs.

One exception was a study that randomly assigned overweight and previously inactive youth to either an after-school soccer program or a group that received health education. Significant increases were found in objectively measured physical activity, and small, but statistically significant, decreases in body mass index at 3 and 6 months in the soccer group compared to the health education group.

Factors that undermine participation by those who could benefit most

A big challenge to making sport a viable solution to obesity is that youth who are already overweight may be unprepared for involvement in sport due to poor fitness levels and underdeveloped motor skills that leave them at a disadvantage when beginning sport.

"Youth who are in this circumstance may need remedial efforts to improve their fitness and motor skill development before they are able to begin competing in sport at the same level with their peers," explain the review authors. "These factors are likely to influence whether youth are involved with sport at all and also whether they are likely to prematurely drop out."

Increased emphasis on nurturing their physical, social and emotional health, along with developing essential life skills though sports and physical activity is what today’s children need more than ever say the leaders of the Youth Sport Trust, a U.K.-based charity dedicated to empowering all young people through sport.

A vision of a world where every child experiences the joys and life changing benefits of play and sport instead of being prone to early onset diseases, worrying about their body image, suffering from anxiety and becoming isolated through the digital age drives the YST's new four-year strategy.

"Children have never been less active and those who are most in need of sport’s transformative powers are the most likely to miss out," says Ali Oliver, the organization’s chief executive. "If we are to help young people discover the joy of movement and nurture happy, active lifestyles, we need to take a radically different approach"

"We also need to focus relentlessly on removing negative experiences from children’s and youth sport."