The study, released online Monday in the journal Pediatrics, found that although the effects weren't huge, children 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.
Also, children 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 study analyzed data on 6,300 students in 40 states.
Daniel Taber from the University of Illinois at Chicago is the lead author of the study. He says the results show that "for these laws to be effective, they need to be consistently strong in all grades."