School-based activity programs should be a key part of efforts to help young people develop healthy habits that last a lifetime, the authors of a review of 26 studies of such programs conclude.

The results underscore the importance of "rethinking the school day so that there are more opportunities throughout the day for kids to be active," Dr. Maureen Dobbins of McMaster University in Ontario, who helped conduct the review, said in a press release.

The World Health Organization has said schools should be a "target setting" for efforts to promote physical activity among young people, Dobbins and her team note in their report in online in The Cochrane Library, which publishes systematic reviews of medical research that offer evidence-based recommendations on health.

The researchers searched the medical literature for studies of school-based activity programs, ultimately identifying 4 with strong methodological quality and another 22 with moderate methodological quality. The studies included children and adolescents 6 to 18 years old, and were conducted in North America, South America, Australia, and Europe.

Seven of the studies actually looked at how the interventions affected the rate or duration of students' leisure time physical activity, the researchers found, while just one looked at activity duration and VO2 max (a measure physical fitness), and one evaluated activity rate and VO2 max.

But there is "good evidence" that the interventions did help children spend more time being active and less time watching TV, Dobbins and her colleagues say. The interventions also appeared to help cut participants' cholesterol and increase their cardiovascular fitness; however, they did not significantly affect students' body mass index or blood pressure.

Just one of the studies reviewed looked at the long-term effects of school-based physical activity interventions, the researchers say, and future investigations must evaluate long-term outcomes.

Programs may be more effective if they get parents involved, according to Dobbins and her team, and when physical education specialists, not teachers without special training, are in charge. "Since school-based physical activity interventions do not cause harm and are associated with some positive effects, such activities should continue," and should be fostered by public health authorities, the researchers conclude.