Although it’s unclear the exact extent that calories count for weight loss, at some point calories do count, and drastically so. I’ve had way too many patients stay in ketosis for weeks, and not lose a pound, because they are eating too many calories. When you stop eating carbohydrates for 2-3 days, your body depletes your liver glycogen suppy, and you go into ketosis. Ketosis means that your body is using free fatty acids instead of glycogen to maintain your blood sugar. But calories count to some extent, even if your insulin level is lower because you are in ketosis, so there is less fat storage. When it’s been studied, patients lose about twice as fast on 1500 calories of protein and fat, compared to 1500 calories of carbohydrate. But this does not mean that you can eat 3000 calories of protein and fat a day, and expect to lose weight. Freely feeding on low carb diets does not work, because the bet is you are going to eat too many calories, and not lose weight.