Keeping track of everything is a huge plus when losing weight but 500-900 calories is not enough to help you lose. Your body will go in starvation mode and you won't lose and when you can't do it anymore because it is way too low to handle for life you will gain 2x more back. I would suggest eating at least 1200 calories and if you are working out even more. You will be amazed at how quicker you will lose.