According to the most recent research, 15 percent of children age 6 to 11 are overweight, more than twice the rate in the mid-1970s. Many reasons for the weight gain have been offered, including the “supersize–me” phenomenon, mothers’ entry into the workforce, and the demise of gym class, but few of the reasons have held up under scrutiny.

A recent study, for example, finds that the extra calories that lead to weight gain are not from the supersized drinks and french fries as much as from simply eating more meals and snacks per day. Likewise, maternal employment explains less than one-ninth of the weight gain among youth in the past 30 years(1).

Given that school is a major part of a child’s day, and about 30 million students eat a federally funded school lunch every day, Assistant Professor Diane Whitmore looked more closely at the school cafeteria as a possible culprit in the obesity epidemic.

Following students in one thousand schools from the time they entered kindergarten until they left first grade, Whitmore finds that children who eat school lunches consume about 40 more calories at lunch (but not at other times of the day) than those who bring their lunch from home. Although 40 calories a day may not seem like much, it adds up. In fact, those 40 additional calories consumed every day leave school-lunch eaters with 2 more pounds than brown-baggers at the end of first grade and they are 15 percent more likely to be obese.

“What’s shocking,” says Whitmore, “is that the difference comes from pretty small margins. As a child, if you overeat just 40 calories a day, you’re going to gain too much weight.” For an adult to gain a similar amount of weight, that would be the equivalent of drinking an extra can of soda a day. “It’s just those few calories that can make a huge difference in obesity rates.”

Of course, factors other than lunch might contribute to an observed weight difference. Being poor, for example, increases the likelihood that a child will eat school-lunch and income has consistently been linked with obesity; or children with weight problems may come from families that place less emphasis on healthy eating. Whitmore accounts for many of these possibilities in her analysis. She finds, for example, that children did not differ in their rates of obesity before entering school. “So the explanation isn’t as simple as families that place less value on health are participating in the school-lunch program,” she says. “Since brown-baggers and school-lunch buyers enter kindergarten with the same weights, the disproportionate gain for school-lunch eaters must be coming from some factor that changed when they entered kindergarten.” The federal government spends about $6 billion each year in direct cash payments to schools for their lunches, serving about 60 percent of the total student population. Although the government has imposed dietary restrictions on school lunches, and most recently passed the School Meals Initiative for Healthy Children, which set guidelines for the recommended daily allowances of calories, vitamins, and fat, Whitmore estimates that only about 4 percent of schools have met the guidelines. “The government spends a lot of money on this program, and yet the schools get to treat it as a free lunch; they can serve unhealthy meals that fail to meet the guidelines with almost no chance of being held accountable.”

Interestingly, although poverty is correlated with obesity, it is not the poorest schools that have the highest-calorie lunches. In fact, it is the wealthier school districts that serve the fattiest foods. These are the schools where pizza and burgers are daily options, and snacks and à la carte items are common.

Although the school-lunch program was conceived as a tool to stave off hunger among poor children—and that goal is still a very real issue—today the program must also begin to balance hunger with obesity, argues Whitmore. “One of the best things government could do is to have a ceiling as well as a floor on calorie counts. And then put some teeth behind it and enforce their own rule.”

Meanwhile, schools can play a role as well. “A lot of schools are on the right track by banning vending machines, but at the same time, they should take a good, hard look at the food they serve their kids and make sure that they’re not serving too much and too many empty calories.” In other words, taking the kid out of the candy store is a start.

Barbara Ray

(1) Cutler, Glaeser, and Shapiro, “Why Have Americans Become More Obese?” Journal of Economic Perspectives 17 (2003), pp. 93–118; Anderson, Butcher, and Levine, “Maternal Employment and Overweight Children,” Journal of Health Economics, 22 (2003), pp. 477–504.