Early infancy as a critical period for development of obesity and related conditions.

The current obesity epidemic has affected even the youngest children in our societies, including those in the first months of life. Animal experiments suggest that the early postnatal period may be critical to development of healthful energy homeostasis and thus prevention of obesity. In humans, observational studies and follow-up of randomized feeding trials show that rapid weight gain in the first half of infancy predicts later obesity and higher blood pressure. Despite the mounting consistency of results, several questions remain to be answered before clinical or public health implications are clear. These include the need for body composition data in infancy and data from the developing world to identify modifiable determinants of gain in adiposity in the early weeks of life, to mount interventions to modify these determinants, to examine tradeoffs of more vs. less rapid weight gain for different outcomes, and to incorporate any interventions that prove to be efficacious into clinical and public health practice in a cost-effective manner.