PARIS — While mulling over ways to get children enrolled in the 4-H Youth Development Group to eat more healthful food, Katy Duval stumbled across something unique: free money.

There was no catch to the offer. Duval, of Poland, who leads 10 children ages 5 to 17 in an after-school program teaching nutrition and healthful lifestyles, was chosen as one of 16 after-school community programs in Maine, Massachusetts and New Hampshire to participate in the “Snack It Up” study looking at how to get children to eat healthier snacks.

Once a week over the spring, Duval redeemed $5 worth of produce at a Hannaford supermarket to make nutritional treats and to learn about how foods affected children’s health. For many, it was their first experience with some of the foods.

Hummus was a standout favorite.

“Kids were definitely on board with the snacks. I was surprised by their reactions,” Duval said. “Peaches seemed to the popular choice.”

Researchers contend that unhealthful snacks have contributed to the rise in childhood obesity rates in the U.S., which, depending on the age group, have more than doubled in the past three decades.

Heather Angstrom and Alyssa Koomas said the program is one of four initiatives at Tufts’ ChildObesity180 program looking at stemming the rise in childhood obesity rates.

The program, which grew out of doctoral research cataloguing the concerns that children did not have access to affordable-but-healthful snacks, targets a specific period when snack consumption is believed to be prevalent: between the time children leave school and return home.

Angstrom said early indications suggest that children who eat with their peers are slightly more likely to eat something new than those who eat on their own. Given the proper incentives, they hope those new foods will be something other than chips and candy.

Early indications suggest that it might: Koomas noted a slight increase in the tendency of people in the study to eat fruit and vegetables than those outside it.

“I don’t think pineapple is the first thought when people think of a snack, but we would like it to be,” she said.

According to Angstrom, options for continuing the program are being explored; one limitation of the study was its size, which they hope to expand.

“It’s hard to say what dollar amount makes the difference in people’s buying choices,” she said.