Two studies, led by Ashlesha Datar and Roland Sturm, looked at food availability in schools and in neighborhoods to investigate how the food environment influences the diet and body mass index (BMI) of children and teens. The two studies differed in measurements, settings and the ages of the kids being studied, but found a surprisingly similar result — that food environment may be less predictive of obesity than originally thought.
How did the studies look at the food environment?
In the school study, the researchers looked at a national sample of 5th graders in public and private schools. The foods and beverages available for purchase at the students’ schools during school hours were analyzed, and the researchers used this information to determine availability of junk food.
In the neighborhood study, the researchers selected a sample of California children and teens and looked at the food outlets within 1.5 miles of their homes and schools. Outlets were categorized as being fast-food restaurants, convenience stores, small food stores, grocery stores or supermarkets.
How did the studies measure the diet?
Both studies used surveys to collect information on diet. The neighborhood study looked at data from a self-report survey (or a parent report for younger children) of the previous day’s diet, focusing on consumption of fruits; vegetables; juice; milk (only for children); soda; high-sugar foods; and fast food. In the school study, researchers analyzed data from two questionnaires given to the students. One collected information on in-school purchases of soda, sweets and salty snack foods during the previous week, while the other looked at overall consumption of healthy and unhealthy foods in and out of school during that same time.
What were the major findings of the two studies?
In both studies, the researchers did not find a connection between the food environments being studied and obesity. In the school study, which looked at consumption inside and outside of school, there was no evidence that kids at schools with high junk food availability consumed more overall than those in schools with low availability. Similarly, the neighborhood study found that the number of supermarkets, fast-food restaurants and convenience stores near children’s and teens’ homes and schools was not closely related to diet quality or BMI.
What could explain these findings?
There are a number of possible explanations. It’s possible that the measures used did not capture important information about the food environment (for instance, many convenience stores have healthy food options and supermarkets have plenty of unhealthy ones), although earlier studies which found a connection between food environment and BMI used the same research methods. Children may have balanced out unhealthy food obtained at school or in their neighborhoods by making healthy food choices at home, or could have been more motivated to eat unhealthy food at home if it was unavailable at school. Also, families are increasingly mobile and may have traveled to get healthy foods even if there were few healthy neighborhood food outlets.
Do these studies mean that access to “junk food” doesn’t contribute to rising obesity rates?
Not necessarily — the connection between food environment, diet and obesity needs more study. Research into environmental impacts on obesity is a relatively young field of study, and the few early studies which found a strong connection between environment and obesity have had a disproportionate impact on public policy. Excess calories are ultimately the cause of obesity, and access to high-calorie, highly processed food is only part of the larger cause.
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School characteristics in the fifth and eighth grades showed little additional influence on the racial and ethnic disparities in body mass index observed at school entry in a longitudinal study of elementary and middle school students.
Focusing only on the availability of particular food outlets in a neighborhood may ignore other important factors, including how families decide what food to buy and where to buy it, availability of healthy foods at home, and parenting practices.
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