2 frozen bananas (I slice them before freezing)
handful of blueberries (approx. a cup)
handful of raspberries (approx. a cup)
a tad of maple syrup (optional)
Throw all together into a food processor and blend. To make it even more quickly, I sometimes just buy a bag of frozen mixed berries and throw half the bag in with the two frozen bananas. I eat the whole thing myself for breakfast each day and stay pretty full most of the morning.
About 500 calories (if you use the maple syrup) and 0 fat