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Laws Limiting School Junk Food Sales and Ads Show Potential to Impact Obesity

Published on August 2, 2016 in Cornerstone Blog · Last updated 2 months 4 weeks ago


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In many cafeterias these days, the sloppy joe special and individual carton of milk comes with a side of state laws. Targeting a childhood obesity rate that seems stuck at a too-high rate of 17 percent, state and local legislators across the U.S. have introduced policy-based efforts to intervene.

They want to reduce children’s risk of becoming obese adults prone to health conditions like heart disease and diabetes by introducing healthy changes in the places where kids spend most of their day, most of the year: schools. Such laws take a range of approaches, such as requiring in-school nutrition education, restricting the sale of junk food in cafeterias and school vending machines, or requiring specific credentials for school food service directors. But there is limited data about the effectiveness of these policies.

“There is a growing body of research about it,” said Deepak Palakshappa, MD, MSHP, an attending physician at The Children’s Hospital of Philadelphia, instructor in General Pediatrics at the Perelman School of Medicine at the University of Pennsylvania, and faculty member in CHOP’s PolicyLab and Clinical Futures. “Most of these studies that looked at specific laws individually found that laws improve children’s diet, but among those that looked at whether they affect obesity, the results were pretty mixed.”

That uncertainty prompted Dr. Palakshappa to study these laws more comprehensively across multiple types of laws in multiple states during his fellowship. His team’s findings were recently published in Preventive Medicine, and he provides an overview on the CHOP PolicyLab blog.

Dr. Palakshappa and CHOP colleagues analyzed data from two national sources to identify possible associations between nine categories of state nutrition laws and childhood obesity. One data source was a classification of the strength of state nutrition laws developed by the National Cancer Institute, and the other was the National Survey of Children’s Health, a comprehensive telephone survey of households that have at least one child under age 18, about the child’s health, health behavior, and environment.

Their main analysis looked at possible associations between the strength of state nutrition laws in 2010 and the weight of children age 10 to 17 in those states in 2011, controlling for state-level differences in children’s weight in prior years and for reported differences between children’s nutrition and physical activity that could affect their weight status outside of school.

They found that two of the nine types of school nutrition laws did have a significant association with lower child obesity. Strong laws limiting the sales of unhealthy or junk foods in cafeterias, vending machines, and school stores (known as competitive food and beverage laws) had a significant association with lower obesity in the 10-year-old, elementary-aged children. And strong laws limiting food and beverage advertising in schools were associated with lower obesity in all ages of youth studied. The other seven categories of laws showed no significant associations.

The type of analysis that the research team performed and the available data could not answer questions about cause and effect, so the associations they detected do not directly answer the question of whether the laws actually played a role in causing changes in children’s weight. However, the new findings should help future research focus in on competitive food and beverage laws and in-school food and beverage advertising laws for further study. Competitive food and beverage laws are the most common state school nutrition laws in the country and have been subject to more study to date, whereas few studies have looked at the comparatively uncommon school food and beverage advertising laws.

Bolstering the possibility that the associations Dr. Palakshappa’s team found might represent an underlying cause and effect relationship: An earlier study that had examined the same two data sources in 2007 found an opposite result, showing stronger state nutrition laws were associated with higher obesity. The researchers on that study hypothesized that states might have imposed stronger laws in response to their locally higher obesity rates.

“If these laws were to have an effect, time would need to elapse,” Dr. Palakshappa said. “Maybe we are starting to see a difference now after several years. It’s hard to know for sure.”