"Overall, our findings showed the interventions to have consistent and significant effects on physical activity and behaviors," Heath wrote. "Even though in some instances the effect sizes of these interventions were rather modest, they were large enough to translate into real population-level benefits if rolled out on a larger scale."

Using mobile phones to get people active

The fourth study found that technology, and specifically cell phone technology, could be significant in helping people get fit.

"With the high prevalence of both physical inactivity and the rapid growth of the mobile phone sector in low-income and middle-income countries, there is a potential for population-level effects that could truly affect global health," wrote Dr. Michael Pratt, a researcher from the Centers for Disease Control and Prevention.

Researchers believe that with more than 4 billion text messaging users worldwide, this could be an effective way to deliver health-conscious messages, particularly in low-income countries.

According to this report, Pratt and his team estimated that using Internet-based technologies could be twice as effective in middle-income countries as in high-income countries, given that 71 percent of the world's population lives in these countries and many have access to cell phones.

"This is a big challenge, but marked progress in countries such as Colombia and Brazil suggests that it is also an achievable challenge," he wrote.

Obesity should be considered a pandemic

The final report suggests that physical inactivity should be recognized as a global pandemic and should be treated like any other infectious-disease pandemic would be.

"The role of physical inactivity continues to be undervalued despite robust evidence of its protective effects," wrote Harold Kohl, a researcher at the University of Texas School of Public Health and lead author of this study. "The response ... has been incomplete, unfocused and most certainly understaffed. ... The effect of this tardiness has been to put physical activity in reverse gear compared with population trends and advances in tobacco and alcohol control and diet."

Kohl called on countries -- low, middle and high-income -- to work across disciplines to fix this problem.

"Physical inactivity is an issue that crosses many sectors and will require collaboration, coordination and communication with multiple partners," he wrote, citing specifically city and community planners, transportation engineers, schools, parks and recreation officials and the media.

He says that almost 75 percent of World Health Organization member countries have some sort of plan to improve physical activity, but only 55 percent of the plans have been put into effect and only 42 percent of the plans in effect are well-funded.

"Substantial improvements in the infrastructure of planning and policy, leadership and advocacy, workforce training and surveillance must be realized," he said.