Switching breasts while breastfeeding is essential to the infant's satisfaction. Allowing newborns to consume all of the milk from one breast before switching to the other enables the child to utilize the infamous foremilk and hindmilk. 

Foremilk and hindmilk are two types of milk that the human breast is producing throughout the breastfeeding period. All of the milk-producing cells in the breasts make identical milk. 

Foremilk quenches the thirst of the infants; it is the milk available when the infant begins eating whereas hindmilk is the milk your infant receives at the conclusion of a feeding which has a higher fat content in that particular feeding which satisfies the hunger of the child.  There is no noticeable difference between foremilk and hindmilk; the transition is quite gradual. According to research conducted by the group of Peter Hartmann, the fat content of milk is primarily determined by the amount of milk in the breast, the less milk in the breast, the higher the fat content.

The length of a feeding does not indicate the amount of fat a baby has consumed. Some infants consume an entire feeding in five minutes, while others require 20 minutes. As long as the infant is adequately breastfed, you may allow him to determine the duration of his feedings, and he will receive all the fat he needs. (DMOIIMadrona/NOIIIFlores/RNPCLaquihon)