Observational studies had suggested that longer-term and exclusive breastfeeding reduces childhood obesity risk.  Nevertheless, observational studies are prone to confounding factors. Hence, investigating the effects of long-term breast-feeding intervention in promoting increased child adiposity and circulating insulin-like growth factor (IGF), which regulates growth, in a randomized experimental studies design will create  internal validity on the said claim within the studied population (Martin, Patel, et .al. 2013).

The randomized trial was conducted in 31 maternity hospitals, in Belarus. It involves approximately 17, 046 breast-feeding mother-infant pairs in 1996 and 1997, but 13 879 (81.4%) were observed/followed up between Jan. 2008 and Dec. 2010 until average age of 11.5 years (Martin, Patel, et .al. 2013).  The breast-feeding protocol used in the study for the experimental group was based on the world health organization breastfeeding program while the other group received usual care (Bakalar, 2013).

At 3 months into the study, 43% of women under the WHO program regime were still breast-feeding, compared to 6% of women in the control group.  By the 6th month, 7.8% of women (WHO program group) and 0.6% of women in the control group were breast-feeding.

The main outcome measures in the study includes body mass index (BMI), fat and fat-free mass indices (FMI and FFMI), percent body fat, waist circumference, triceps and sub-scapular skinfold thicknesses, overweight and obesity, and whole-blood IGF-I. In addition, Analysis was based on intent-to-treat (without imputation), which accounts for clustering within hospitals and clinics (Martin, Patel, et .al. 2013). 

The result generated in the study shows that the BMI, percentage body fat and prevalence of obesity were slightly higher among children breast fed longer than in the control group.  However, the differences were not statistically significant (Bakalar, 2013).

Randomization ensures   internal validity within the population being studied.  In addition, the randomization refutes the observational study claim, which suggests that longer breast feeding decreases childhood obesity.  Nonetheless, randomization may not fix the external factors or assume external validity in this trial (cultural, nutritional, or regional differences). Therefore, it is difficult to use a randomized trial outside it studied population as a generalization standards for every other situation. Nevertheless, Dr. Emily Oken, an associate professor of population medicine at Harvard emphasized, “There are lots of good reasons to breast-feed…and just because we saw no evidence for obesity doesn’t mean women should stop breast-feeding.” (Bakalar, 2013).

References

Bakalar, N. (2013). Breast-Feeding May Not Lead to Leaner Children.  Retrieved from             http://well.blogs.nytimes.com/2013/03/14/breast-feeding-may-not-lead-to-  leaner-   children/.

Martin, R., Patel, R., Kramer, M., Guthrie, L., Vilchuck, K., et. al (2013). Effects of          Promoting   Longer-term and Exclusive Breastfeeding on Adiposity and Insulin-like      Growth Factor-I at Age 11.5 Years: A Randomized Trial. JAMA, 309 (10), 1005-1013.        doi:10.1001/ jama.2013.167. Retrieved from http://jama.jamanetwork.com /article.aspx?articleid=1667089.