Do kids prefer cheap healthy food or expensive junk food?

When I was a kid, school lunches didn't offer choice. I paid $1.10, and I was given four plops of foodlike substance. The entrees had names like "salisbury steak," "lasagne," or "beef stroganoff," but they all tasted about the same. Our "vegetable" was usually overcooked peas or green beans. There was a "starch," like mashed potatoes or a roll, and a dessert -- Jell-O or a cupcake -- typically the only edible item on the tray. If our lunch money wasn't stolen on the way to school, we were at least in theory presented with a balanced meal.

By the time my kids were in school, cafeteria philosophy had changed. Instead of serving up glop that no one ate, kids were given "healthy choices." They had charge accounts (no more stealing lunch money), and could select whatever they wanted to eat from a variety of options. What I don't understand is how the school nutritionists didn't realize that most kids were going to take three Jell-O's, two chocolate milks, and skip everything else. Jim regularly racked up charges of almost $10 a day. Needless to say, it didn't take long before we started resorting to homemade lunches.

I've finally found a study that addresses my concerns about putting children in charge of their own nutrition. A team led by Leonard H. Epstein gave 10- to 12-year-olds "budgets" to buy food in a laboratory setting. Then they varied the price of the foods to see if kids would modify their behavior: If we make junk food more expensive than healthy food, will kids substitute healthier foods?

In the first experiment, the kids were given bites of six healthy foods (like tomatoes, carrots, and grapes) and six unhealthy foods (like chocolate chip cookies, M&Ms, and potato chips). Each child picked their favorite healthy and unhealthy food. They were given $5 worth plastic tokens with which to "buy" their favorite foods, which they were told could vary in price. They were encouraged to buy as much as they wanted, since they could always save some for later. In one task, the price of the healthy food varied in $.50 increments from $.50 to $2.50, while the price of the unhealthy food stayed constant at $1.00. After each "purchase" was made, the kids got $5 more for the next purchase.

The results were as expected: kids bought more of the less expensive food -- whether healthy or unhealthy, and less of the more expensive foods.

But this experiment didn't exactly replicate the real world, since different kids have different amounts of money available to spend (and in the case of my kids' school, they had infinite budgets!). So Epstein et al. devised a new experiment, with 10- to 14-year-olds, this time varying both the budget and the prices of the items. When looking at only purchases of healthy or unhealthy foods, the results were similar to the first experiment:

For every budget level, as price went up, kids bought less of the item in question. However, the picture changes when we look at the relationship between price of one item (in this case, unhealthy foods), and purchases of the other item:

When we consider the low-budget group, as price of unhealthy foods increases, purchase of healthy foods increases -- this makes sense, and is in line with the first experiment. But for the high-budget group, as price of unhealthy foods increases, kids buy less healthy foods. Kids will spend an increasing portion of their budget to buy unhealthy foods, even as their price increases.

Epstein and his team note that overweight and obesity is increasing in America, but their experiments do suggest one way to help kids choose healthier foods: keep them on a limited budget, and increase the price of unhealthy foods compared to healthy ones.

Indeed, we've applied a similar tactic to our (now middle school-aged) kids' lunch budget. We give them $5 per day for lunch, and we allow them to keep the change for themselves. Suddenly the same kids who claimed they couldn't survive on the $7 to $8 they were spending in the school cafeteria are now spending $1 a day or less at the grocery store, making their own lunches, and saving the change for iPods and computer games. Whether this trade-off is ideal remains to be seen, but at least we're spending less on school lunches!

Epstein, L.H., Handley, E.A., Dearing, K.K, Cho, D.D., Roemmich, J.N., Paluch, R.A., Raja, S., Pak, Y., & Spring, B. (2006). Purchases of food in youth: Influence of price and income. Psychological Science, 17(1), 82-89.