• Posted October 2, 2023

Breastfeeding in Infancy Tied to Healthier Weight Later for Kids

What a baby eats, or how the baby eats, may have an impact on future weight and health, research has shown.

A new study backs that up. It found that 9-year-olds who had been breast-fed for six months or more had a lower percentage of body fat than their peers who were never breast-fed or received breast milk.

The researchers also found that kids who were not given soda before 18 months of age also had less fat at age 9.

Past studies have zeroed in on links between infant feeding and obesity based on body mass index (BMI) -- an estimate of body fat based on height and weight. This one relied on what researchers considered a more precise measure: percent fat mass. That's the proportion of total weight owing to body fat.

“Infancy is a vulnerable life stage characterized by significant developmental changes, and when environmental exposures may have long-lasting effects on an individual's metabolism and physiology,” said lead researcher Catherine Cohen. She is a post-doctoral fellow at the University of Colorado Anschutz Medical Campus in Aurora.

“This study provides initial data to support that the types of foods introduced during infancy may be involved in predisposing individuals to more (body fat) accrual in childhood; also, these behaviors could represent targets for interventions aiming to prevent the onset of obesity and related metabolic diseases,” Cohen added.

The researchers analyzed data on more than 700 mother-child pairs who participated in the Healthy Start study, investigating how a mother's lifestyle and environment during pregnancy affects her child's growth and development.

Moms completed interviews when their babies were 6 and 18 months old, answering questions about feeding, including whether baby was breast- or bottle-fed, and when the child was introduced to table foods.

Infants were grouped by length of breastfeeding, age when they started eating complementary foods and when they were introduced to soda.

About two-thirds of babies were breast-fed for at least six months, while 73% began eating table foods at 5 months or older. Most babies, 86%, didn't have soda until after 18 months.

At age 5, the proportion of body weight that could be attributed to fat was nearly 20%, on average. At age 9, it was 18%.

While infant feeding patterns weren't linked to body fat at age 5, both shorter breastfeeding duration and early soda introduction were associated with faster increases in body fat between those two checkpoints and with higher percentage of body fat at age 9.

Infants breast-fed fewer than 6 months had 3.5% more body fat at age 9 compared to their counterparts who were breast-fed for longer.

Babies introduced to soda before 18 months of age had 7.8% more body fat on average at age 9.

Introduction of complementary foods did not appear to be connected to percent fat mass.

“The association we found between early soda exposure and later (body fat) accrual in childhood also aligned with our hypothesis and, in fact, appears to be even stronger in magnitude than the effect of breastfeeding,” Cohen said.

“However, thus far, there are fewer studies to compare this finding to and supports the need for more research focused on the quality of complementary foods introduced during infancy and toddlerhood, as this could also be an important predictor of later risk of obesity,” Cohen noted.

As for why babies who were breast-fed for a shorter period would have more body fat at age 9, Cohen suggested in a news release that it could be due to nutrient differences between human milk and formula. It could also have to do with appetite regulation. The impact of human milk on the infant microbiome is also not yet clear.

Dr. Michelle Katzow, medical director of the POWER Kids Weight Management Program at Cohen Children's Medical Center in New York City, said the findings are consistent with past research.

Differences in children's fat mass could owe to a number of variables, Katzow said.

They may involve not just breast milk itself but whether breastfeeding is at the breast versus breast milk given from a bottle.

“It may be that there's some components of breast milk that in some way are protective, certainly affects the microbiome. The microbiome affects weight and obesity in ways that are still very much unknown,” Katzow said.

“But another thing that we know from other studies is that there's something about feeding at the breast that teaches babies how to regulate their intake in a way that they don't learn quite as well from a bottle," Katzow said. “This has been studied a lot, but it's still not totally clear.”

Babies learn to do the work involved in extracting the milk, but also to stop when they're done. On the mother's part, there isn't the visual of milk left in a bottle.

More recent work has looked at teaching people to bottle feed in a way that responds specifically to an infant's cues.

A key takeaway: Soda, or any sweetened drink, is not necessary for infants and toddlers, Katzow said. That includes juice.

“Encouraging people to breastfeed who are interested in breastfeeding and making it doable for them in the workplace, in the community, taking away stigma is really important,” she added. “I think just as important is not stigmatizing people who choose not to breastfeed or can't. And I think that that piece often gets lost in … the health realm where when we talk about the benefits of breast milk and lactation and breastfeeding.”

The findings were scheduled to be presented Tuesday at a meeting of the European Association for the Study of Diabetes in Hamburg, Germany. Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.

More information

The U.S. Centers for Disease Control and Prevention has more on sugar-sweetened beverages.

SOURCES: Catherine Cohen, PhD, RD, postdoctoral fellow, University of Colorado Anschutz Medical Campus, Aurora; Michelle Katzow, MD, assistant professor, pediatrics, Zucker School of Medicine at Hofstra/Northwell, and medical director, POWER Kids Weight Management Program at Cohen Children's Medical Center, New York City; presentation, European Association for the Study of Diabetes meeting, Oct. 3, 2023, Hamburg, Germany