No, the way you're describing it sounds like it's going too far.
I mean, don't get me wrong, when I say you need to match your consumption with your exertion, the obvious way to do that is to increase your exertion -- I.E. get some exercise. And also to eat more balancedly.
But 800 calories is ridiculous -- even Weight Watchers will tell you not to go overboard like that.
I mean, these blind numbers like "1500 calories to maintain your weight" is ridiculous. How much exercise are you getting with that diet? And don't try and tell me it doesn't matter, 'cause it does. Someone who's sedentary and gets no exercise will have different dietary requirements than someone who walks three times a week will have different dietary requirements than Michael Phelps, who basically exercises non-stop, so his dietary requirements are fairly high.