Junkfood Science: Fact or Fiction? Kids today are fat because they’re not getting enough PE

April 12, 2009

Fact or Fiction? Kids today are fat because they’re not getting enough PE

One of the most popular answers to childhood obesity is physical education. Countless governmental health and school officials have enacted programs to increase physical activity to combat childhood obesity. Are these interventions grounded on sound scientific understandings of the causes of obesity and have they been shown to have any effect on child obesity?

A new study — the largest systematic review of the evidence on school-based physical activity interventions to date — provided some answers. But few parents heard about this major international review.

Calls for increased PE to slim down young people are based on widespread beliefs that today’s generation of young people are telly tubbies, who get little physical activity and spend their days plopped in front of television and computer screens. The image being portrayed in media is “of a fat, lazy and physically feeble generation,” said Michael Gard, a physical and health educator at Charles Sturt University’s Bathurst campus, and co-author of The Obesity Epidemic. “There is more than a hint of disgust in these words…I have a great deal of trouble matching this image with the children I know, most of whom are busy, active, lively young people.”

Nor, as we’ve seen, does the evidence support popular beliefs about fat children or that parents have cause to worry that their children or teens are headed for the morgue. As fitness research has continued to find, there is no credible evidence that physical activity programs reduce obesity or that levels of physical activity and fitness among fat children are less than thinner kids to explain the diversity in sizes.

Even the most comprehensive and intensive School Nutrition Policy initiative — that incorporated every school-based intervention recommended by the U.S. Centers for Disease Control and Prevention in its Guidelines for Promote Lifelong Healthy Eating and Physical Activityfound “no differences between intervention and control schools in the prevalence of obesity” or that the program had any effect on BMIs even after two years.

But few parents ever hear the evidence. Nor have many heard about this latest study by pediatricians in Vancouver, British Columbia. They reviewed every randomized, controlled study of school-based physical activity interventions, with BMI data and lasting a minimum of 6 months, that has been conducted since 1966. They found a total of 18 studies involving more than 18,000 children, mostly elementary school age, that could be included in their analysis. The studies included were of good methodological quality, designed to be fair tests of the interventions, and the funnel plot showed no evidence of publication bias.

They published their findings in the March 31st issue of the Canadian Medical Association Journal. They found:

The change in BMI was not significantly different between children who received a school-based physical activity intervention and those in the control group (weighted mean difference –0.05 kg/m2; 95% CI –0.19 to 0.10). This indicates that body composition did not improve with physical activity.

The authors went on to analyze the data in multiple ways, attempting to parse out an effect. They specifically examined the studies that had included other interventions intended to control weight, such as school nutrition policies, and there was no change in the findings. Nor did the duration of the interventions have any statistical effect on their findings. They also compared the highest quality studies with the lower quality studies to see if that might influence the results and even that “had no effect on the results.” Nor did the gender of the children involved in the studies make any difference.

Not one study found physical activity interventions improved BMI. Only three reported an effect on any body composition measurement (body fat percentage, waist measurement, waist-to-hip ratio, triceps skinfold thickness, subsapular skin fold thickness, total lean mass, total fat mass, and skin fold sum) with physical activity interventions. One study demonstrated a deterioration with physical activity interventions and 14 found no change.

As they concluded: “Current population-based policies that mandate increased physical activity in schools are unlikely to have a significant effect on the increasing prevalence of childhood obesity.”

Mainstream media and most of the public works from one point of view — that today’s children are fat and slovenly and more structured PE in school would shape them up. It is taken as fact and so obvious and intuitively correct that no evidence is needed. So, the evidence that counters popular beliefs continues to be ignored and the prejudices that condemn, ridicule and medicalize an entire generation of healthy, happy children continues.

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