In the long run, encouraging a baby to finish the last ounce in their bottle might be doing more harm than good.
Though the calories soon burn off, a bad habit remains.
Brigham Young University sociology professors Ben Gibbs and Renata Forste found that clinical obesity at 24 months of age strongly traces back to infant feeding.
"If you are overweight at age two, it puts you on a trajectory where you are likely to be overweight into middle childhood and adolescence and as an adult," said Forste. "That's a big concern."
The BYU researchers analyzed data from more than 8,000 families and found that babies predominantly fed formula were 2.5 times more likely to become obese toddlers than babies who were breastfed for the first six months.
But, the study authors argue, this pattern is not just about breastfeeding.
"There seems to be this cluster of infant feeding patterns that promote childhood obesity," said Gibbs, lead author of the study that appears in Pediatric Obesity.
Putting babies to bed with a bottle increased the risk of childhood obesity by 36 percent. And introducing solid foods too soon – before four months of age – increased a child's risk of obesity by 40 percent.
"Developing this pattern of needing to eat before you go to sleep, those kinds of things discourage children from monitoring their own eating patterns so they can self-regulate," Forste said.
Forste said that the nature of breastfeeding lends itself to helping babies recognize when they feel full and should stop. But that same kind of skill can be developed by formula-fed infants.
"You can still do things even if you are bottle feeding to help your child learn to regulate their eating practices and develop healthy patterns," Forste said. "When a child is full and pushes away, stop! Don't encourage them to finish the whole bottle."
Breastfeeding rates are lowest in poor and less educated families. Sally Findley, a public health professor at Columbia University, says the new BYU study shows that infant feeding practices are the primary reason that childhood obesity hits hardest below the poverty line.
"Bottle feeding somehow changes the feeding dynamic, and those who bottle feed, alone or mixed with some breastfeeding, are more likely to add cereal or sweeteners to their infant's bottle at an early age, even before feeding cereal with a spoon," said Findley.
The next project for Gibbs and Forste is to reevaluate the link between breastfeeding and cognitive development in childhood. Forste has previously published research about why women stop breastfeeding.
"The health community is looking to the origins of the obesity epidemic, and more and more, scholars are looking toward early childhood," Gibbs said. "I don't think this is some nascent, unimportant time period. It's very critical."
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