School children in Philadelphia spent an average of $1.07 on snacks at local corner stores and got about 357 calories for their money, Kelley Borradaile, PhD, of Temple University, and colleagues reported in the Nov. 5 issue of Pediatrics.
"That was one of the more surprising findings, that a little over a dollar can purchase about 360 calories," Borradaile said.
She added that just 25 cents "can purchase eight ounces of a sweetened fruit drink, a bag of chips, candy, gum, even a popsicle."
Research has shown that childhood obesity is higher among ethnic minorities, and the communities in which they live often have a disproportionate number of corner stores.
In Philadelphia, Borradaile said there are multiple corner stores within a four-block radius of any given school.
To document the nature of children's purchases in corner stores near their schools, the researchers surveyed a total of 833 fourth- through sixth-graders at 24 corner stores before and after school. The students were from 10 urban elementary and middle schools, and the surveys were conducted between January and June 2008.
Most students in the schools were black (54%) or Hispanic/Latino (22.9%).
The researchers found that the most frequently purchased items were energy-dense, low-nutritive foods and beverages, such as chips, candy, and sugar-sweetened beverages.
"They were buying . . . pretty much what you would expect would be popular among children," Borradaile said.
On average, students spent $1.07 on 2.1 food items and 0.5 beverage items per purchase.
Total number of calories per purchase was 1,497.7 kJ, or about 356.6 kcal.
"For the most frequent shoppers, those who shopped both before and after school, five times per week, this would amount to about 712 calories per day, or 3,560 calories per week," the researchers said.
About 30% of calories came from fat, 23% from protein, and 66% from carbohydrates. More calories came from foods than from beverages.
Chips were the most frequently purchased item, accounting for more than a third of all purchases, followed by candy.
Among beverages, artificially flavored "fruit" drinks were the most popular, accounting for 45.7% of all liquid purchases.
The researchers also assessed purchase habits by time of day.
In the morning, kids spent an average of $1.19 on 2.3 items for about 390 calories, the most popular foods being chips, then candy, followed by beverages and gum.
In the afternoon, they spent about $0.94 on 1.8 items for a total of 317 calories, the most popular being chips, then beverages, followed by candy and frozen treats.
More than half (53%) reported shopping at the corner store every day, and 21.9% reported doing so two to four times per week.
Borradaile said switching to baked rather than fried chips would reduce caloric intake by about 14.3%, and purchasing water instead of sugar-sweetened beverages would decrease purchases by about 60 calories each time.
The findings also highlight the need for better obesity prevention efforts, Borradaile said, adding that efforts to enhance dietary quality among children in urban settings should take into account corner store environments near schools.
Future interventions might involve targeting children through nutrition education in schools, social marketing, or providing incentives for healthier purchases.
The study may have been limited in that data may not be generalizable outside of fourth- through sixth- graders.
The study was supported by grants from the Robert Wood Johnson Foundation.
Dr. Foster serves on the scientific advisory board for Con Agra Foods and has served as a consultant to General Mills. He has also received funding for research grants on the role of almonds (Almond Board of California) and diet beverages (Coca Cola Company) on adult obesity.
Zalman S. Agus, MD Emeritus Professor
University of Pennsylvania School of Medicine and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner