Does infant feeding choice affect later risk of obesity?

Strategies to prevent overweight and obesity are needed to protect against its adverse long term health effects such as high blood pressure, cardiovascular disease and diabetes. Could the choice of feeding breast milk or infant formula from birth have an effect on the infant's future risk of obesity? This question is explored by Koletzko et al in a recent article in the American Journal of Clinical Nutrition (1).

Infancy is a time of rapid growth and it is during this time that the infant is said to be "programmed" for later health and disease risks, a result of the actions of hormones, metabolites and neurotransmitters on the brain and other organs. Genetics and the environment ultimately interact to determine adult health risks. Studies have shown that high birth weight infants are at greater risk of later obesity and that high weight gain duriing the first 2 years of life is a strong predictor of being overweight when starting school at age 5-6 years.

Breast fed and infant formula fed infants grow differently, with formula fed infants at 12 months being heavier and longer. Children breast fed during infancy have a lower prevalence of overweight and obesity when starting school compared to those formula fed, and the longer they were breast fed the less overweight or obese they are. The protective effect of breast feeding compared to infant formula could be due to  the different sucking patterns used by the infant, the more frequent feeding, the shorter intervals between feeds and breast milk's unique and changing composition. 

The hypothesis currently being explored is that breast feeding protects against obesity and early weight gain because it is lower in protein. The protein content of infant formula per kilogram body weight is about 50%- 80% higher than breast milk. High protein intakes in excess of needs stimulate insulin and insulin like growth factor 1 (IGF1) resulting in increased adiposity and weight gain. High protein diets can also decrease human growth hormone secretion resulting in  reduced fat breakdown. The European Childhood Obesity Project, a double blind randomized controlled trial is currently underway to test this hypothesis (2).  Infants born at term were assigned either a low protein (7% of energy starter; 9% follow on) or a high protein (12% of  energy starter; 18% follow on) infant formula during  their first year. Initial results at 2 years of age show that the infants on the lower protein formula have similar growth to breast fed babies. Reducing the protein content of infant formula may have the potential to decrease later risk of obesity in formula fed infants.

Reference:

1. Koletzko B, von Kries R et al. Can infant feeding choices modulate later obesity risk? Am J Clin Nutr 2009;89(suppl):1502S-8S

2. European Union Childhood Obesity Programme www.childhood-obesity.org