Actually I just asked my nutritionist this last week because I use myfitnesspal to journal my food and found that some days I only get 5-600 calories, which worried me this is not enough. She said she was not worried about the 800 calorie days, but I needed to work on the below 800 calorie days. They (my nutritionists) really don't use calories in what I'm supposed to eat as they focus on protein and carbs, but I still see the calories and just think that is too low, even if I'm not hungry.