How School Environments Affect BMI

March 05, 2014

Could school be an influential environment for children to try new foods?

There is room for improvement at schools in terms of food and physical activity offerings to help promote healthier weights in adolescents, according to a new report from Urban Institute in Washington D.C. and published in a recent issue of the Journal of the Academy of Nutrition and Dietetics. The report found strong correlations between school environments and adolescent BMI (body mass index).

Children spend a third of their day at school, making school an important intervention point for healthy behaviors – especially with the shocking fact that in 2010, 16.9% of children were obese. Unfortunately, many unhealthy food options from vending machines or other sources exist, and students are not exposed to as much physical activity as they should be. However, previous studies have been inconsistent in this field of research, with some studies pointing to a great effect on BMIs and others pointing to no effect at all.

“School is an important intervention point for healthy behaviors because children spend a lot of time there and their diets and physical activities are under the supervision of teachers and other staff. While children cannot be compelled to make healthy food and activity choices, schools can provide healthy environments in which students can make healthier choices,” says study author Dr. Tracy Vericker.

To gain clarity on the topic, researchers looked at 8th graders (730 boys and 820 girls) living in low income households in 2007, and estimated the relationship between child BMI and the school physical activity environment, student school-related physical activity choices, the school food environment and student participation in federal school meal programs. 

Unfortunately, they found that about one quarter of low-income boys (24%) and one fifth of low-income girls (20%) in this study were obese – several points higher than the national average. These same students spend more than two hours a day using video games, computers or TV, and majority of these students (73% of boys and 77% of girls) eat at a fast food restaurant at least once a week.

When it comes to sports, students on average spend three days a week participating in a physical education program, with about half participating in school sports (58% of boys and 53% of girls). Low-income boys that participated in school sports had BMIs that were 0.55 points lower than those for boys who did not participate in sports at school, although for girls, there was no difference.

Eighty-five percent of boys and 84% of girls have access to unhealthy foods and beverages in school. Case in point? Most of the students (93%) ate the school lunch, which was associated with a 0.65-point higher BMI score for low-income girls. Low-income girls also had a 0.70-point higher BMI when they ate a school breakfast, however, only 39% typically ate the school breakfast. Ninety percent of girls ate the school lunch. It’s important to note that at the time of this sample, the new federal school meal regulations were not yet in place. Vericker says that future research should examine if the new standards, designed to boost nutrition and reduce fats and salt, improve on these numbers.

Deborah Beauvais, RDN SNS, Spokesperson for the Academy of Nutrition and Dietetics, points out that sweeping changes were indeed made to school nutrition programs in the 2012-2013 school year, with guidelines created for portion sizes across all the food groups and overall calorie ranges for each age/grade group. Thus, if we were to do this research with the current meal patterns, says Beauvais, we may see very different results, as Vericker also suggests.

However, Beauvais adds that we should take caution in solely looking at school activity and school meals. Children spend, on average, 175 to 180 days in school. If students were to eat both breakfast and lunch each day they attended school that would be approximately 350 to 360 meals from the school environment. But students spend 185 to 190 days out of school as well. Therefore, nearly the same number of days are spent outside of the school day as are spent at school – and the home food environment should also be taken into consideration.

“One more thing to consider is the preteen age of the 8th grade population. There are many social-emotional factors that drive the choices children make in the school environment. I have observed first hand children change their food choices based on what the ‘cool’ kid picks for lunch. Often, these choices have little to do with student preferences, but more to do with fitting in with their peer group,” says Beauvais.

Yet another frustrating factor are the hours spent dong homework, which are associated with higher BMIs for girls. For every hour of homework logged, BMI values went up by 0.02 points. Girls spent an average of nine hours per week doing homework, while boys spent an average of seven hours per work. Boys’ BMIs were not affected by homework hours though. More research could look at the relationship between homework and obesity, says Vericker.

Clearly, improvements can be made in both the school food and physical activity environments. However, multiple strategies need to be employed because boys and girls do not seem to respond in the same ways to these environments. Ultimately, though, the school environment is a great place to educate kids about healthy food choices, says Beauvais.

“The school environment allows students the opportunity to taste a variety of new foods that maybe they do not get at home. My hope is that they try a new food at school and then ask Mom or Dad to buy it for home too. Yes, the school environment can contribute to healthier food options and increased physical activity, but we must also consider the time out of school and the healthy or unhealthy behaviors at play there too.”