Its not as simple as fewer calories in then out equals weight loss. That doesn't bother to take insuluin into account at all. Many people on LC started out on low calorie diets, but found they didn't lose weight, or even gained some. It was the bodies insulin reaction, not the calories in of themselves. I'd highly recomend you see if your library has the Protien Power book, as it goes into the science of how insulin plays a part in weight, blood pressure, and other health issues.

Atkins does state that calories are important. However on a moderate protien low carb diet you can consume more and lose then on a high carb diet because it takes more energy to burn fat for energy then to burn gluclose. For most people if they eat when hungry and stop when satisfies, not stuffed feeling, they probably won't be getting to many calories. Some do have to watch it though. If it was as simple as calories in and out though, there would be no need for an LC diet. We could eat the same number of calories from just carbs and still be losing.