Breastfeeding Reducing Childhood Obesity: Fact, Fiction or Sometimes?

Over the past 3 decades, an increasing number of studies and reviews have examined the relationship of breastfeeding and childhood obesity. The authors of Agency for Healthcare Research and Quality’s (AHRQ) Evidence Report on Breastfeeding meta-analysis concluded that children who were breastfed for at least 3 months were less likely to be obese than those never breastfed, taking into account multiple confounding factors.¹ The duration of breastfeeding was found to be inversely related to the risk of being overweight; each month of breastfeeding being associated with a 4% reduction in risk. A WHO meta-analysis from 2007 also concluded that longer breastfeeding (typically durations of 3 to 9 months), in comparison to no breastfeeding, was associated with lower rates of obesity.² The Framingham Offspring study noted a relationship of breastfeeding and a lower BMI in adults.³ A sibling difference model study showed that the breastfed siblings weighed 13 pounds less than formula fed siblings at a mean age of 14 and were less likely to reach BMI obesity threshold.⁴ Based upon these studies, the promotion of breastfeeding to prevent obesity has been recommended by the CDC, the Institute of Medicine, and the Surgeon General.

However, there are, however, other important studies that failed to find a relationship. The PROBIT study, the only randomized trial of breastfeeding in term infants, randomized an intervention to promote increased duration and exclusivity of breastfeeding in Belarus and found no significant differences in BMI, percent body fat, and obesity between the experimental and control group children at 11.5 years of age.⁵ The “discordant sibling study” looked at data obtained from the National Longitudinal Survey of Youth study and found that breastfeeding was not associated with significant improvements in childhood obesity when siblings who were fed differently during infancy, one breastfed, the other bottle fed, were compared.⁶

So how are we to interpret these conflicting studies? My opinion has been that, as the etiology of obesity is multifactorial, breastfeeding can play an important role in its prevention, but is unlikely to entirely prevent it. The limitation of most of these studies is that they look at breastfeeding alone. Future studies need to focus on the role of multiple modifiable factors on these conditions.⁷ 

A recent study suggests a different solution.⁸ It suggests that the relationship of breastfeeding and childhood obesity may only be true in certain infants and only with longer durations of breastfeeding. Investigators from New York studied the effect of breastfeeding duration on weight-for-length z score trajectory from 0 to 24 months. Elevated weight-for-length (WFL) trajectories were measured as excessive weight gain in infancy has been linked with obesity later in life. Data for the study were obtained from 438 mother-infant pairs who were enrolled in the Bassett Mothers Health Projects and who had frequent growth measurements from birth to age 2. The heights and weights were obtained from medical charts to calculate WFL z scores by using the WHO 2007 growth standards. Individual risk factors associated with weight gain trajectories were included in an obesity risk index. Logistic regression analysis was performed to investigate whether the association between breastfeeding duration and weight gain trajectory varied across obesity risk groups. Latent class modeling revealed rising and stable weight gain trajectories. Children with rising trajectory were more likely to have mothers with higher BMI, less education, and who smoked during pregnancy. Children were assigned obesity risk scores based on the number of these risk factors to which they were exposed. Low risk was 0 risk factors, medium 1 risk factor and high risk 2 or 3 risk factors.

Children who had a high obesity risk score and who were breastfed for <2 months were more than twice as likely to belong to a rising rather than stable weight gain trajectory than children at high risk who were breastfed for >4 months (OR, 2.55; 95% CI, 1.14–5.72, p = .02).

Limitations of the study include the lack of differentiation of exclusive and partial breastfeeding and the lack of information on early supplementation of solids. However, the study suggests that the relationship of breastfeeding and childhood obesity may only be true in infants with a high risk for obesity and only in infants who were breastfed for at least 4 months. This result is consistent with a recent study of over 4,500 twins in the UK found that breastfeeding for longer than 4 months was associated with lower growth velocity.⁹

So, does breastfeeding lower the risk of childhood obesity? My conclusion is yes; but only in infants at higher risk for obesity and are breastfed for longer durations. In addition, as obesity is multifactorial, breastfeeding alone is unlikely to entirely prevent it. This study, however, adds to the evidence that breastfeeding should remain one of multiple recommended practices to stem the obesity epidemic.

References

1. Ip S, et al. Breastfeeding Medicine. 2009;4(1):17-30. A Summary of the Agency for Healthcare Research and Quality’s Evidence Report on Breastfeeding in Developed Countries | Abstract
2. Horta B, et al. Geneva: World Health Organization; 2007. http://whqlibdoc.who.int/publications/2007/9789241595230_eng.pdf
3. Parikh NI, et al. Am J Med. 2009;122(7):656–663; doi:10.1016/j.amjmed.2008.11.034 http://www.ncbi.nlm.nih.gov/pubmed/19559168
4. Metzger MW, et al. Am J Hum Biol. 2010;22(3):291–296. http://www.ncbi.nlm.nih.gov/pubmed/19693959
5. Martin RM, et al. JAMA. 2013;309(10):1005-1013. http://jama.jamanetwork.com/article.aspx?articleid=1667089
6. Colen CG, Ramey DM. Soc Sci Med. 2014;109:55-65. http://www.ncbi.nlm.nih.gov/pubmed/24698713
7. Gillman MW and Ludwig DS. NEJM. 2013:369(23):2173-5. http://www.nejm.org/doi/full/10.1056/NEJMp1310577
8. Carling SJ, et al. Pediatrics 2015; 135 (1): 111-119. http://pediatrics.aappublications.org/content/early/2014/11/25/peds.2014-1392.abstract
9. Johnson L, et al. International Journal of Obesity. 2014. http://www.ncbi.nlm.nih.gov/pubmed/24722545

Larry Noble MD, FABM, IBCLC is a neonatologist and Associate Professor of Pediatrics at the Icahn School of Medicine at Mount Sinai in New York City, and a Board member of ABM.

Blog posts reflect the opinions of individual authors, not ABM as a whole.