There are three to four times as many fast-food restaurants within less than a mile of schools than would be expected if the restaurants were evenly distributed around the city of Chicago.

The city is representative of other large metropolitan areas that face the same problem, according to the researcher who conducted the study. "Children and teens are surrounded by unhealthy options," says lead author Bryn Austin, an assistant professor of pediatrics at Children's Hospital in Boston.

Students can pick up fast foods, including hamburgers, french fries, fried chicken and doughnuts, on the way to and from school, Austin says. Some high school students can go off campus at lunchtime to eat it, she notes. "Five days a week we send children to an environment where there's an abundance of high-calorie, low-nutritional-quality, inexpensive food."

More Calories, More Fat, More Sugar

The news comes amid growing concerns that American schoolchildren are gaining weight. About 31% of kids ages 6 to 19 are overweight or at risk of becoming so, according to the latest government statistics. Many school systems, including Chicago, are offering healthier snacks and beverages in vending machines, school stores and a la carte lines.

Other studies show that on days when kids eat fast food, they have more calories, more fat, more sugar and fewer fruits and vegetables than on other days. On a typical day, one-third of US children and teens consume fast food, researchers say.

Austin and colleagues at Children's Hospital and Harvard School of Public Health used several mapping strategies to identify the locations of 613 fast-food restaurants in Chicago and compare them with the locations of 1,292 public and private kindergartens, elementary schools, middle schools and high schools.

The top 10 restaurant chains in the Chicago area are McDonald's, Subway, Dunkin' Donuts, KFC, Burger King, Popeye's Chicken and Biscuits, Wendy's, Church's Chicken, Taco Bell and White Castle, according to the study. Among the findings:

Fast-Food Free Zones?

Yale University obesity expert Kelly Brownell says this could undo nutrition advances being made in schools. "There should be zoning laws that prevent this type of exploitation of children. Just like there are drug-free zones around schools, there should be zones around schools that are free of junk food, including fast-food restaurants, mini-markets and gas stations that sell food inside."

But Dan Mindus of the Center for Consumer Freedom, a Washington, DC-based group backed by the restaurant and food industry, says the study doesn't make a case for new zoning laws.

"This study provides no evidence that fast-food restaurants are purposefully trying to locate near schools," he says. "All it shows is that restaurants locate in areas where adults shop and work."

Michael Vaughn, a spokesman for Chicago's public school system, which has about 426,000 students, says: "Our main concern is making sure that students have healthy meals and healthy food while they are at school.

"We got rid of pop, candy and chips from the vending machines. We feel that sends the right message to our students about their health and the types of choices they should make when it comes to what they eat."