School-Based Physical Activity Interventions Ineffective for Childhood Obesity

Katherine A. Kahn, DVM

October 14, 2008

October 14, 2008 (Boston, Massachusetts) — School-based physical activity interventions to address obesity in children have no effect on body mass index (BMI) or other anthropometric measures of overweight or obesity, a systematic review of the literature concludes.

Lead investigator Kevin C. Harris, MD, presented the results of a meta-analysis here at the American Academy of Pediatrics 2008 National Conference and Exhibition. Dr. Harris is a pediatrician at the BC Children's Hospital in Vancouver, British Columbia.

Lifestyle approaches are the cornerstone of the prevention and treatment of childhood obesity; however, these approaches are fraught with poor compliance, Dr. Harris told session attendees.

"School-based interventions are theoretically appealing because compliance with interventions can be improved. Consequently, many local governments have enacted or are considering policy mandating increasing physical activity in schools, although the efficacy of these interventions in improving body composition remains unproven," Dr. Harris said. "Therefore the objective of our study was to determine whether school-based physical activity interventions can improve body composition as measured by BMI in children."

Dr. Harris and colleagues identified 398 studies initially; however, only 18 met all inclusion criteria, and 15 of those were amenable to meta-analysis. Ten of these were randomized controlled trials and 5 were nonrandomized controlled trials. "We recognize that it's difficult to engage schools in randomized controlled trials," Dr. Harris told attendees.

Overall, data from 13,003 children aged 5 to 18 years were included in the meta-analysis. All studies involved school-based physical activity that took place only during regular class time. The minimum duration was 6 months. Half of the studies were shorter than 1 year in duration (range, 6 months – 3 years). Height and weight were measured before and after the intervention, not self-reported. The majority of studies included some type of cointervention, such as diet, education, or family involvement.

Meta-analysis of the data revealed that the difference between intervention groups and the control groups in mean change in BMI was −0.05 kg/m2 (95% confidence interval, −0.19 to 0.10), indicating that BMI is not affected by school-based physical activity intervention. There was also no consistent improvement in any other measures of body composition, such as body fat percentage, skin-fold thickness, lean mass, waist circumference, and waist-hip ratio.

Researchers also conducted sensitivity analyses to assess whether important study characteristics might have influenced the results. Sex, study duration, and trial quality had no effect on the results. Changes in BMI was found to be virtually identical between the intervention and control groups in the sensitivity analyses, and regression analysis showed that results were also remarkably consistent across studies, Dr. Harris told session attendees.

"We're very concerned that the results of our study might be taken out of context," Dr. Harris told Medscape Pediatrics. "There are important beneficial health effects from school-based physical activity interventions, such as improved aerobic capacity, blood pressure, bone mineral density, and flexibility. We should be promoting physical activity in school and outside of school. But if we're really going to tackle the issue of obesity, then we need to have interventions that are proven to impact BMI and other anthropometric measures."

Dr. Harris stressed that providing nutritious food in school and optimizing children's nutritional intake and restricting access to unhealthy foods should be a key component of any school-based intervention.

Robert Murray, MD, chair of the executive committee of the American Academy of Pediatrics Council on School Health commented on the analysis to Medscape Pediatrics. "It is an excellent review, but it brings out that working with obesity in schools is very complex," he said.

Dr. Murray stressed that there are many factors — both lifestyle and genetic predisposition — that contribute to the childhood obesity epidemic. "I've seen the conclusion many times that school-based interventions don't work," he told Medscape Pediatrics. "The truth of the matter is they don't work for the stated outcome, which is weight. If you improve kids' fitness level and diet — even if you don't change their BMI — their health outcomes will improve, which is what we are looking for from a medical perspective. I just think BMI is a lousy outcome measure."

The authors have disclosed no relevant financial relationships.

American Academy of Pediatrics 2008 National Conference and Exhibition: Abstract 300. Presented October 12, 2008.

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