by Sheryl Rifas-Shiman

Almost 14 years ago, I remember being very excited — and a bit confused — about when to start feeding my baby solid foods. The when, what, and how of starting solids was a hot topic among parents at the playground. Since that time, recommendations have changed but haven’t necessarily become clearer. National and international guidelines recommend not feeding an infant solid food until at least 4 months of age and preferably not until 6 months. The American Academy of Pediatrics and World Health Organization advocate for later introduction of solids as a way to promote exclusive breastfeeding for 6 months. When I was making this decision, I remember being mostly concerned about choking and allergies. But there may be another reason for delaying the introduction of solids: preventing obesity.
In a study done as part of Project Viva, several colleagues and I examined the extent to which starting solids before 4 months was associated with childhood obesity among breastfed and formula-fed infants.

Project Viva is a cohort study in Eastern Massachusetts that has been following children since before their birth. In our study of 847 children, among infants who were never breastfed or who stopped breastfeeding prior to 4 months of age, those who received solids early (before 4 months) were 6 times more likely to become obese than children who received solids later. This relationship was not explained by rapid early growth.

The situation was much different among breastfed infants. Among infants who were breastfed for at least 4 months, there was no link between when solid foods were introduced and becoming obese.

Our results were published in the journal: Pediatrics.

One possible reason why formula-fed infants were at risk of becoming obese after early solids, but not breastfed infants, is that formula-fed infants may simply eat more when solids are introduced. Breastfeeding may promote self regulation of an infant’s consumption. Breastfeeding mothers may learn to recognize their infants’ satiety cues, thereby reducing feeding to compensate for the solids.

Breastfeeding typically leads to later introduction of solids anyway

Interestingly, in our study breastfeeding itself was associated with timing of introduction of solids: 8% of breastfed infants started solids before 4 months compared with 33% of formula-fed infants. Also, in the Project Viva cohort, breastfeeding was associated with less obesity in early childhood: 7% of breastfed children were obese compared with 13% of formula-fed children.

Despite these findings, there remains a big controversy about the protective effect of breastfeeding on obesity; new evidence has found no relationship.

Our results support recommendations to introduce solids after 4 months of age, at least among infants who are formula-fed. This seems to be a good rule of thumb for breastfed infants too. Holding off on the solids might promote longer exclusive breastfeeding, which reduces infection and allergy-related outcomes, and may even increase IQ!



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