Parenting and personality work together to affect baby's weight gain

The researchers studied the babies' temperament and how their mothers soothed them when the babies were six months old. When the researchers followed up a year later, they found that the more the mothers used food to soothe, the more weight certain babies gained.

The effect was only seen in babies with surgent temperament -- characterized by being more outgoing, active and drawn to new things and people.

Cynthia Stifter, professor of human development and psychology, Penn State, said the results suggest that when parents give surgent babies food when they're not hungry -- when they're trying to calm them, for example -- those babies may be more likely to later eat for pleasure, rather than just when they're hungry.

"Surgent children tend to have greater reward sensitivity than other kids -- and thus greater sensitivity in the dopamine area of the brain," Stifter said. "So if food, which is highly rewarding, lights up that area quickly and intensely, they may make a stronger connection between food and feeling good, causing them to seek out food more often in the future."

Previous research has linked surgent temperament with greater weight gain and higher body mass index, but few studies have examined how a baby's temperament affects how parents feed their children. Stifter said the results are an example of how a baby's temperament can influence how his or her parents choose to parent.

"When babies respond to things in a certain way, parents pick up on that," Stifter said. "So in many ways, the baby's behavior is influencing the parents' behavior. If a parent wants to stop their child from crying, and they know that food will do that, they may use that strategy, particularly if other methods are not working."

The researchers asked 160 mothers to keep a three-day diary about how often their babies cried and what they did to calm them when the babies were six months old. The babies' temperament were also evaluated by both the parents and the researchers, who noted traits related to anger, fear, sadness, activity levels, smiling and laughing, and how the child reacted to new things and people, among others.

The researchers followed up a year later, when the children were 18 months old, to measure how much weight the babies gained in the previous year. They found that the more parents used food to soothe their babies when they weren't hungry, the more weight those babies gained, but only if those infants were also observed as having a surgent temperament.

The effect wasn't seen in non-surgent babies whose parents used food to soothe or in surgent babies whose parents did not use food to soothe.

Stifter said that parents may be tempted to use food to calm a crying baby because it's effective. But she added that using food as a reward can ultimately lead to overeating, especially in surgent children, and be a risk for developing obesity later on.

"Surgent kids tend to get bored easily because they're always looking for something new to capture their attention," Stifter said. "So if they're bored, and this connection has been set up in their brain between food and feeling good, they may turn to food, not out of hunger but because they're looking for something to do."

Stifter said that while there's no guarantee that these kids will turn out to be obese, other research has shown that quick, rapid weight gain puts them at risk. She said the study's results -- recently published in the International Journal of Obesity -- could be used to design new ways to educate parents about feeding their babies.

"I'd like to see parent education programs have a temperament component, to teach parents more about what their child's temperament means for them," Stifter said. "I'd also like to see these programs teach parents about hunger cues so they know when their babies are hungry, so as to avoid using food to soothe their babies when they are not hungry."