Nearly one in five children in the United States is obese, according to the most recent estimates from the Centers for Disease Control and Prevention.

A new study by Pennsylvania State University that linked overeating to the brain's response to food rewards may help shed light on the national epidemic that can lead to type 2 diabetes, high blood pressure, and breathing problems.

Among the kids in the study, a high responsiveness to food rewards, rather than money, indicated a higher likelihood to overeat and to eat even when they weren't hungry. The researchers measured responsiveness using blood-oxygen-level dependent imaging (BOLD) on an fMRI scan, which indicates the locations in the brain with the most activity. The results remained the same regardless of the children's weight and body mass index.

Responsiveness "was happening independently of if the child had obesity, so the parent might not even realize that their child is on a trajectory to overeat," said Shana Adise, coauthor of the study and current postdoctoral fellow at the University of Vermont. Adise worked on the study while completing her Ph.D. degree at Penn State.

Certain food habits as a child, such as an inability to stop eating or a tendency to hide snacks, can indicate an unhealthy relationship with food. Even if the child has a healthy BMI, such habits might precede obesity later in life.

Parents should avoid behaviors that put a lot of emphasis on food, such as using food consistently as a reward and, even, restricting kids' access to food, said Kathleen Keller, coauthor of the study and an associate professor in the department of nutritional sciences and food science at Penn State.

"Children are still developing, so this is a really critical period of time," Adise said. "Things could become a permanent habit later in life."

The 59 children in the study, aged 7 to 11, visited a lab on four occasions. Once, they ate a meal to establish a baseline appetite. That same day, 20 minutes later, they were offered more food to judge their tendency to eat when they aren't hungry. Another time, the children were offered a buffet of food to measure their proclivity to overeat.

At the final session, the fMRI scanned the children's brains while they played a guessing game and were given a food, money, or neutral reward for a correct answer.

The researchers found children whose brains were more excited by food rewards also had a tendency to overeat at the buffet and eat when not hungry.

"People who are vulnerable to overeating, they are people who value food over other types of rewards," Keller said. "It's clearly starting at a time when children are young, before they develop obesity."

However, certain eating behaviors might have been exacerbated in the study. Because the children only met four times and were served foods that they may not have been exposed to at home, their eating habits in the lab may not necessarily mimic normal eating habits perfectly.

"This is the beginning of the road," Adise said.