Dropping a handful of quarters into the waiting palm of a lunch lady is quickly getting replaced by rapid, blurry swipes of a debit card, and the proliferation in cafeterias around the country has two researchers pushing for greater monitoring of children’s unhealthy spending habits.

Cornell University behavioral economists, David Just and Brian Wansink, recently investigated the school lunch choices of 2,314 tiny consumers around the U.S. The team compared calorie counts in meals purchased in schools that were debit-only to those that accepted both cash and debit cards. Meals purchased in debit-only schools not only had more calories than in other schools, but also contained a greater number of calories from high-fat, high-sugar foods.

“There may be a reason for concern about the popularity of cashless systems,” the researchers said in a university press release. “Debit cards have been shown to induce more frivolous purchases or greater overall spending by adults and college students.”

While the team didn’t examine how much children spent according to the two systems, they found the types of food consumed were significantly different. Students at cash/debit schools consumed an average of 721 calories per meal. Meanwhile, debit-only students ate 752 calories. Moreover, cash/debit students typically consumed 378 calories in non-healthy food items alone — such as ice cream, cheeseburgers, French fries, candy, and chips — contrasted with the 441 calories ingested by diners in debit-only cafeterias.

Debit cards not only make spending easier; they eliminate the physical act of depleting a wallet of its cash. For the fiscally unwise teenager, this could spell disaster when it comes to responsibly handling Mom or Dad’s finances. Pulling money from a wallet sends an immediate signal to a person that he or she now has less of it. Simply swiping a piece of plastic blinds them to the actual damage that’s being done.

There’s also the health toll of spending blindly, which is arguably more costly. Childhood obesity has reached near epidemic proportions in the U.S., with obesity rates having more than doubled in children and tripled in adolescents over the last 30 years. In 2010, more than a third of all children and adolescents were overweight or obese.

Debits cards could very well facilitate this trend, particularly if parents or schools don’t take concerted efforts to ensure kids are spending money wisely, and in healthful ways. Not doing so could very well “lead children to generally greater spending on lunch,” the researchers argue.

One possible remedy is to nudge kids toward cash options, which can help break patterns of unhealthy spending — because as the researchers note, kids who pay with a debit card aren’t doing so because it gets them closer to unhealthy food. It’s just easier to buy more, which means it’s easier to buy more unhealthy food.

Introduce incentives into the cafeteria and maybe kids will drift away from plastic and gravitate back toward paper, the researchers concluded, adding that a “cash-for-cookies” program could be one potential way to “encourage students to think twice before making their selection.”

Source: Just D, Wansink B. School lunch debit card payment systems are associated with lower Nutrition and higher calories. Obesity. 2013.