500 calories less a week is a pound a week in pure fat, 100 is 2 pounds, itisn't safe to really push past that.
http://www.bmi-calculator.net/bmr-calculator/
that site can help, but you have to read up and use the righ formula for what you need to do, hope this helps.
Do you mean 500 calories/day and 1000 calories/day for a week?
