Human milk changes in its composition throughout lactation as your baby grows and is constantly changing to meet the needs of the baby from the first few days of colostrum to beyond the baby’s second year. The composition of your milk can change  from day today especially as hormones ab and flow with your menstrual cycles. They can change during a given day  based on your stress levels, how often your baby feeds, and how well your baby MDs your breast. But did you know that the composition of your milk can also change during an individual feeding  and from breast to breast?!?!  As the baby eats, protein and fat content rise in the milk. There is actually 4 to 5 times more fat and 1 1/2 times more protein present at the end of the feeding than at the beginning. The baby may consume nearly 18% of their calories between minutes 11 and 16 of a feeding.  The fat content at the beginning of a feeding is around 1% milk fat. By the end of a 15 to 20 minute feeding, the fat content can be as high as 4 to 5%! By comparison, whole milk contains just 3.25 percent milk fat.  Fat content varies from mother to mother and from feeding to feeding. The amount of fat in breastmilk is dependent on the length of time between feedings, the degree of breast fullness, and the length of time the baby sucks at the breast. To put it simply, the emptier the breast, the higher the fat content. The fuller the breast, the lower the fat content. By trying to “stretch” a baby to scheduled feedings actually decreases the fat content in a mothers milk. It is always best to feed baby on demand.