HealthDay News — Body mass index (BMI) increases in middle school students can be limited by school-based nutrition policies but not by physical activity policies, according to a study published in the January issue of the American Journal of Preventive Medicine.

Jeannette R. Ickovics, PhD, from the Yale School of Public Health in New Haven, Connecticut, and colleagues assessed the effectiveness of implementing school-based nutrition and physical activity policies (eg, alternatives to food-based rewards/celebrations and opportunities for physical activity during/after school) on student BMI trajectories at 12 randomly selected schools in an urban district. Students were followed for three years during middle school (2011 to 2015; 595 students). 

The researchers found that students at schools randomly assigned to receive support for nutrition policy implementation had healthier BMI trajectories over time. The magnitude of improvement was greater over time, with cumulatively significant effects 3 years postintervention. Students at schools randomly assigned to receive the nutrition intervention had an increase in BMI percentile of <1% vs students in other conditions, whose BMI percentile increased 3 to 4%. For students in schools randomly assigned to physical activity policy implementation or not, there was no difference in BMI. Eighth-grade students at schools randomly assigned to the nutrition condition consumed fewer unhealthy foods and sugar-sweetened beverages and ate less frequently at fast-food restaurants. 

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“This is some of the strongest evidence we have to date that nutrition education and promoting healthy eating behaviors in the classroom and cafeteria can have a meaningful impact on children’s health,” a coauthor said in a statement.

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