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Study: Formula feeding affects gut bacteria and obesity risk

Study: Formula feeding affects gut bacteria and obesity risk


Claudia Boyd-Barrett

posted in Parenting

Exclusively breastfeeding your baby during the first few months of life helps her develop healthy bacteria in her tummy, reducing her risk of becoming overweight, a new study suggests.

Formula feeding, on the other hand, appears to change the microbial environment in babies’ guts and increase their risk for obesity, according to the study published in JAMA Pediatrics.

Researchers in Canada studied data on more than 1,000 babies during their first year of life. The babies’ moms reported whether they breastfed exclusively, supplemented with formula, or fed their infants with formula only during the first few months. The researchers also took samples of the babies’ poop at around 3 months and at 1 year old.

At age 3 months, about half of the moms exclusively breastfed their babies, 16 percent only fed their babies formula, and a third gave their babies both breastmilk and formula. The researchers found that breastfed babies had the highest levels of beneficial bacteria in their guts (as detected in their poop), and this continued through age 1. Formula-fed infants, meanwhile, had the lowest levels of these bacteria and a proliferation of other types of microbes that are more common in older children and adults.


What babies ate appeared to affect their weight too. The exclusively formula-fed infants had about double the risk of becoming overweight compared to breastfed-only infants. Partially breastfed babies had a 60 percent greater risk of becoming overweight, the study found.

Lead study author Meghan Azad told ABC News that breastmilk contains complex sugars that feed specific types of bacteria in the gut, and these in turn affect how children’s bodies burn and store fat, and how they use energy.

Other factors, such as birth by C-section, excessive weight gain during pregnancy, and exposure to chemicals in plastics have also been linked to childhood obesity. These latest findings offer one more possible contributor, and underscore the benefits of breastfeeding.

The American Academy of Pediatrics recommends exclusive breastfeeding for the first six months (although any amount of breastfeeding is beneficial). Check out BabyCenter’s breastfeeding resource page for help with your breastfeeding journey.

What do you think of this latest study’s findings? Do they surprise you?

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