States with strict laws on the quality of food in school vending machines appear to have healthier students.
Researchers at the University of Illinois at Chicago studied over 6,000 students from 40 states.
They found those who lived in areas with strict, consistent laws for competitive foods -- which include school sales of junk food and sweetened beverages -- gained less weight from fifth to eighth grade.
States with weak laws were similar to those without any school snack rules in that their students either gained weight or stay the same.
Experts not related to the study say it is impossible to tell whether school vending machines were responsible for the students' weight loss or whether other factors were at play.