MONDAY, March 30 (HealthDay News) -- Physical fitness programs in schools improve many aspects of children's health, but they don't appear to combat obesity, a new study in the Canadian medical publication CMAJ shows.

Improvements in blood pressure, muscle mass, bone mineral density, lung capacity and flexibility were some of the benefits experienced by the more than 18,000 students participating in "physical activity interventions" at their schools; however, the program's did not noticeably lower the children's body-mass index (BMI) -- a common measurement of obesity.

The study authors, from the BC Children's Hospital in Vancouver, concluded that the program's overall health benefits still warrant their inclusion in school curriculum, even if they don't reduce obesity.

The failure to reduce BMI scores might have been because the programs did not offer enough vigorous activity or that other outside factors may have had a greater effect on weight, the authors suggested.

The rate of childhood obesity in the United States has tripled in the past 40 years and similar increases are occurring in Canada and most of Europe, according to background information in the article.

Louise Baur, from the University of Sydney in Australia, in a commentary in the same issue of CMAJ, writes that reversing trends in childhood obesity requires a broader, long-term approach -- from healthier school meals to changes in how cities are developed so that they encourage more physical activity.

"No simple or short-term changes, such as a physical activity intervention for a limited length of time in the school curriculum, can be expected to influence the prevalence of obesity," wrote Baur, who specializes in children's health.

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Related MedlinePlus Pages:

• Exercise for Children
• Obesity in Children
• School Health