A child's neighborhood or food environment plays a big role in the kinds of food choices they make. After all, children and teens are more restricted to the environment they live in than adults, and this limits their choices when it comes to buying food. Just as adults' commutes can lead them to buy junk food, kids' routes home from school affect the kind of food they buy.

Canadian researchers studied the trips to and from school of about 650 students, ages nine to 13, for two weeks. Each child wore a GPS logger that detected when they came within 50 meters (164 feet) of a fast food restaurant or store where they might purchase junk food and recorded the amount of time they were there. The children also logged any purchases they made in a diary.

When parents drove their kids to school it was much more likely there would be a stop to purchase unhealthy food.

The results showed that one in 20 exposures to places that sold junk food resulted in an unhealthy purchase, and the more times the child was at a location, the more likely they were to buy something unhealthy. It was during the trips home from school that kids were most likely to purchase junk food.

Children who traveled to and from school by bus did not make any junk food purchases for obvious reasons, but when parents drove their kids to school it was much more likely there would be a stop to purchase unhealthy food. Even students who walked or rode their bikes to school purchased less junk food than those who were driven. Girls were more likely to purchase junk food than boys.

“This study provides strong evidence that a child's surrounding food environment affects their food purchasing behaviour,” Jason Gilliland of the Children's Health Research Institute, and Director of the Human Environments Analysis Laboratory at Western University, said in a statement.

The study not only points to the need to educate students about making healthy food choices, it shows that parents need educating, too. Parents don't always realize the powerful influence they have over their children’s eating habits. Stopping for a high calorie treat after school is a nice moment to share with your kids, but maybe a juice bar would be a better choice, if there is one on the way home. Or, to avoid an argument, simply arrive with healthy ready-to-eat snacks to take the edge off after school hunger immediately.

The study has implications for decision makers who manage the environments of children and adolescents — city planners, school board members and public health officials. Perhaps policies need to be adopted or changed that restrict the number of fast food restaurants and convenience stores near schools.

The study is published in the Canadian Journal of Public Health.