Eliminating junk foods at schools may help prevent childhood obesity

"This is one of the very first comprehensive investigations that examined whether childhood obesity trends changed after new statewide policies were enacted in California," said the study's first author Emma Sanchez-Vaznaugh, assistant professor of health education at SF State. The Robert Wood Johnson Foundation Healthy Eating Research, New Connections Program funded the $100,000 project.

Childhood obesity is increasingly prevalent in the United States, with obesity rates more than tripling during the last 30 years. Today, one in three children is either overweight or obese. Last year, Centers for Disease Control and Prevention researchers reported the first leveling of these child obesity rates. However, there were no reasons given as to why trends might have stalled.

Between 2003 and 2005, Governor Shwarzenegger signed SB 677, SB 965 and SB 12 into law, the first comprehensive set of statewide policies to eliminate sodas and other highly sweetened beverages and restrict the sale of junk foods in all of California's public schools. Although many other states subsequently enacted similar standards, potential effects on childhood obesity were uncertain.

Sanchez-Vaznaugh and co-investigators used eight years of body mass index (BMI) data from fifth and seventh grade students collected as part of California's annual Physical Fitnessgram testing. The study compared BMI trends in the years preceding the enactment of the legislation with the years following the legislation. The data show that before the policies took effect, the rate of overweight students was increasing among all groups in the study (girls and boys in fifth and seventh grades). However, in the three year period after the policies became effective, the increase in the number of overweight children was significantly reduced among fifth-grade boys and seventh-grade students of both sexes throughout California. The pre- and post-policy trends in overweight were not significantly different among fifth-grade girls.

The researchers also looked at children in the Los Angeles Unified School District (LAUSD) separately, because the district passed slightly stricter, but otherwise similar policies in their district the year before the passage of California's SB 677. Prior to the implementation of the policy there was an upward trend of overweight fifth and seventh-grade students in the Los Angeles area. When the researchers compared these trends in the period after the new policies were implemented, they found that the increasing trend in the number of overweight fifth-grade students in the Los Angeles significantly slowed. There were no significant changes among seventh-grade students in Los Angeles.

"Although policymakers cannot directly influence student behavior, our study shows that governmental policies can help define the environment in which children learn to make food choices and thus shape the food behaviors, influencing overweight trends in entire student populations," Sanchez-Vaznaugh said. She also cautions that there is still a lot to do to stem obesity in California's public schools.

She cites school campus proximity -- particularly in poorer neighborhoods -- to stores selling unhealthful foods and beverages that stand in opposition to nutritional objectives set by the U.S. Department of Agriculture. Limited resources and budget cuts hamper schools from offering both healthful, good-tasting alternatives and physical education programs. "Only about 40 percent of children in our study were considered physically fit," Sanchez-Vaznaugh said.

In addition to teaching at SF State, Sanchez-Vaznaugh is a Kellogg Health Scholar at the University of California San Francisco's Center on Social Disparities in Health. The study's senior author was Patricia Crawford, director of the Dr. Robert C. and Veronica Atkins Center for Weight and Health at University of California, Berkeley. Co-investigators were Brisa Sanchez and Jonggyu Baek from the University of Michigan.