But if the laws have even a tiny effect, "what are the downsides of improving the food environment for children today?" asked Dr. David Ludwig, an obesity specialist at Harvard Medical School and Boston Children's Hospital. "You can't get much worse than it already is."
Children in the study gained less weight from fifth through eighth grades if they lived in states with strong, consistent laws versus no laws governing snacks available in schools. For example, kids who were 5 feet tall and 100 pounds gained on average 2.2 fewer pounds if they lived in states with strong laws in the three years studied.
Also, children who were overweight or obese in fifth grade were more likely to reach a healthy weight by eighth grade if they lived in states with the strongest laws.
The effects weren't huge, and the study isn't proof that the laws influenced kids' weight. But the results raised optimism among obesity researchers and public health experts who generally applaud strong laws to get junk food out of schools.
"This is the first real evidence that the laws are likely to have an impact," said Dr. Virginia Stallings, director of the nutrition center at Children's Hospital of Philadelphia. Stallings chaired an Institute of Medicine panel that urged standards for making snack foods and drinks sold in schools more healthful but was not involved in the new research.
The authors of the study, released online Monday in the journal Pediatrics, analyzed data on 6,300 students in 40 states. Their heights and weights were measured in spring 2004, when they were finishing fifth grade and soon to enter middle school, and in 2007, during the spring of eighth grade.
The researchers also examined several databases of state laws on school nutrition during the same time. The states were not identified in the study because of database license restrictions that protect the students' confidentiality, the authors said.
