Infants with a hearty appetite grew more rapidly and might be genetically predisposed to obesity, according to two linked papers published Monday in the US journal JAMA Pediatrics.

The first paper, by Professor Jane Wardle of University College London, England and colleagues, revealed that infants with a heartier appetite grew more rapidly up to age 15 months, potentially putting them at increased risk for obesity.

The authors used data from non-identical, same-sex twins born in the United Kingdom in 2007, who differed on questionnaires measuring appetite and satiety, and whose weight was measured from birth up to age 15 months.

Within pairs, the infant who was more food responsive or less satiety responsive grew faster than their co-twin, said the study. The more food responsive twin was 654 grams heavier than their co- twin at six months and 991 grams heavier at 15 months. The less satiety responsive twin was 637 gram heavier than their co-twin at six months and 918 grams heavier at 15 months.

"It might make life easy to have a baby with a hearty appetite, but as she grows up, parents may need to be alert for tendencies to be somewhat over-responsive to food cues in the environment, or somewhat unresponsive to fullness," said Wardle, lead author of the study. "This behavior could put her at risk of gaining weight faster than is good for her."

The second JAMA Pediatrics paper, in collaboration with King's College London, shed further light on the way that appetite, particularly low satiety responsiveness, acts as one of the mechanisms underlying genetic predisposition to obesity.

The researchers accessed data from 2,258 10-year-old children born in the United Kingdom between 1994 and 1996. The team used 28 obesity-related genes to create a polygenic obesity risk score ( PRS) for each child to estimate their genetic susceptibility to obesity. Higher PRS scores indicated a higher genetic predisposition to obesity.

The PRS scores were then examined to determine the correlation with the children's satiety responsiveness and adiposity, or body fatness.

"As expected, we found that children with a higher PRS score ( more obesity-risk' genetic variants) were likely to have larger BMI (body mass index) and waist circumference," said Clare Llewellyn, lead author from the University College London. "But more importantly, we also found that these children were more likely to have low satiety responsiveness.

The findings suggest that satiety sensitivity could be targeted for pharmacological and behavioral interventions, to prevent or treat obesity, said the researchers.

"For example, children with lower satiety sensitivity could be taught techniques that might improve their fullness signals when eating, such as slowing their eating speed," Llewellyn said. " Another approach might be to provide better advice to parents and children about appropriate portion sizes, limiting access to ' second helpings' and ensuring tempting treats are out of sight between meals."



In a related editorial, Daniel Belsky of the Duke University Medical Center said that the papers show that the obesogenic environment does not affect all children equally.

"The fact that children confronted with similar environmental circumstances experience disparate outcomes has been attributed to genetic factors," Belsky wrote. "But just what these genetic factors are and just how they contribute to individual differences in response to the obesogenic environment remains, if not entirely a mystery, an enduring puzzle."