I doubt any single meal each day is going to prevent fat loss. And 600 kcal for breakfast isn't excessive. I'd suggest you try calorie cycling. See my post on that: http://worldfitnessnetwork.com…..same-time/ .
Either way, if you are eating x calories a day (or 7x a week) and are not losing, then you are burning less than 7x calories a week. Basic law. I've never – I mean never – known anyone accurately measuring their calories. Everyone makes mistakes – for example, did you know that food manufacturers are not required to be 100% accurate on their labels? Right there you can have a 10% variation. The only time it's accurate is in a highly controlled lab setting. Then, trying to measure calories burned is nearly impossible. So, it's fine to count calories because it provides a basis; but it's just the starting point. You have to dial things up and down until you start seeing results.
Stick with it, keep experimenting, and you'll get it !