The one in the left is definitely more fatty. You can tell by the color and it is less transparent.

One of the biggest reasons you might be seeing so much foremilk is if you are pumping several ounces in addition to feeding baby. This will cause your supply to remain higher than needed, which can lead to full and stiff breasts, forceful letdown, and plugged ducts.

If you absolutely must pump because you are going back to work soon and need to build up a stash of milk for the caregiver, just pump a few minutes on the side baby just ate on. This way the milk you store will be fatty. You don't need to pump both sides! If the side baby didn't eat on is uncomfortable, pump or hand express a tiny amount to relieve the pressure, but not a full bottle amount.

Contrary to popular belief, your breasts don't continue producing the same amount every day. When empty, the breast fills. When stimulated by sucking or pumping, the hormone prolactin tells your body to make more. This means that pumping both sides tells your body you need more milk than baby is eating, which will make it harder for baby to get to the hindmilk.

Hope that helps!

foremilk vs hindmilk