800 calories is very low
you can't possibly get all the recommended nutrients/vitamins in that low a calorie intake. My worry would also be that if you reach a plateau at 800 calories there isn't much leeway to cut calories to lose more weight...
My recommendation would be to bring your calories up very gradually about 100cals/day every week till you are at least at 1200 to 1400 calories/day which is the a healthy number of calories to lose weight at.
Do you exercise you don't mention exercising... If you exercise you can eat a bit more and keep losing weight...
Good luck, oh, and CONGRATS on your weight loss ...