Do school-based obesity interventions really work?

‘Science-ish’ looks at the evidence behind taking the anti-obesity fight to the classroom

Alan Cleaver/Flickr

We’re fatter than ever and efforts to reduce our ever-expanding waistlines are failing, according to a new report by the Community Foundations of Canada.

Between 1981 and 2009, obesity roughly doubled across all age groups and tripled for youth (age 12 to 17) in Canada. This translates to a rate of obesity that’s close to 25%.

Our padded figures have left governments scrambling to address the chronic condition. Carrying extra weight increases the risk of a range of health conditions (from Type 2 diabetes to high total cholesterol and several cancers), meaning health-care costs balloon with our waistlines. (The Community Foundations of Canada put the price tag on health spending related to obesity at between $4.6 and $7.1 billion each year.)

Some jurisdictions are getting creative in response to the so-called obesity epidemic. Denmark just became the first country in the world to impose a ‘fat tax’ or surcharge on foods that contain more than 2.3% saturated fat, including much-loved greasy staples like pizza, butter, and cheese.

Here and abroad, schools have taken it upon themselves to turn out healthier students. Calgary schools have banned junk food—a practice a number of boards in this country have adopted—and two Niagara schools recently announced they are taking part in an exercise program that requires schoolchildren to exercise vigorously for 20 minutes before class.

Though the impact of the fat tax on portly Danish people will not be known anytime soon, there is a growing evidence base about obesity interventions in our schools. So, do they work?

First, let’s look at the evidence about school-based physical activity programs. Dr. Maureen Dobbins (PhD), associate professor in the school of nursing at McMaster University, has authored two systematic reviews on the subject (the newest will be published in the coming months). Overall, she found that while these programs get kids to spend more time during the day being physically active, reduced blood cholesterol, and increased VO2 max (aerobic capacity), the extra exercise did not produce a reduction in Body Mass Index. There was also little impact on the amount of exercise taken in leisure time.

Her advice? “I don’t see a reason not to keep going down this road of encouraging more activity during school time, but the research suggests it’s one part of a complicated approach to promoting physical activity in children. If we’re able to achieve more children being more physical active during the school day, it is one piece of what needs to happen.”

In Europe, studies on promoting exercise among European teenagers led to similar conclusions. A 2009 review of 20 trials on the effectiveness of interventions to promote physical activity among the EU’s teenagers found that “school-based interventions generally lead to short term improvements in physical activity levels” but these improvements in activity levels had “no conclusive transfer to leisure time physical activity.”

As for school interventions that mixed both diet and exercise, a review looked those in 2009 (along with programs that involved only increased physical activity or dietary changes). The University of Melbourne’s Dr. Elizabeth Waters (PhD), one of the researchers on the study and the lead on a soon-to-be-released updated review on the subject, spoke to Science-ish about the work, which builds on over 15 years of tracking intervention research conducted under trial conditions.

She said the latest review was actually more promising than previous studies: it showed some reduction in BMI from interventions that focus on nutrition and physical activity, particularly in a school setting. “Overall, the evidence is mounting now that (school-based) interventions are more likely to be effective,” said Dr. Waters. “The differences observed could equate to a significant population change if implemented across all schools and settings, and sustained over school generations.” However, her work also suggested that benefits while children are at schools tend to be lost or reduced during leisure time. For Dr. Waters, this means “we need to work on sustaining these benefits outside of the school environment.”

If given the chance to change policy, what would Dr. Waters do? She told Science-ish that she’d take a holistic approach and integrate healthy eating, physical activity, and body image components into the curriculum, as well as policies to increase the availability of healthy food in cafeterias and decrease the availability of unhealthy foods. She’d also build more exercise time into school hours, and create supports for parents to make healthy lifestyle choices at home.

So it seems the best quality science demonstrates what we already know: there’s no magic bullet solution for the obesity epidemic.

Science-ish is a joint project of Maclean’s, The Medical Post, and the McMaster Health Forum. Julia Belluz is the associate editor at The Medical Post. Got a tip? Seen something that’s Science-ish? Message her at julia.belluz@medicalpost.rogers.com or on Twitter @juliaoftoronto

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