I actually thought it was a mix of the low cal and low carb... when you're in ketosis, ketones are produced and this makes your body use the fat we have as fuel, so in effect your body has switched from a carbohydrate burning engine to a fat burning engine.
You would obviously loose weight by eating low cal no matter what you ate, but the carbs definitely paly a huge part in it, if ou started eating carbs you'd come out of ketosis and your body would switch again, and stop using the fat you have as the source but the carbs.
The reduced hunger is just a bonus from ketosis.