You can look up your brm, basal metabolic rate and calculate how many calories you burn under normal circumstance, add in exercise

let's say that's 3,000 calories per day
if you're only eating say 2,000 calories per day, then you're at a 1,000 cpd deficit, and since it takes 3,500 calorie deficit to lose one pound of body fat, then it will take you (conceivably) 3.5 days to lose one pound, or about 2 pounds per week

you can expedite this only up to a point by eating less because your metabolism slows significantly, but you can counter this by exercising because then it cannot be so slow

so, if you really need to lose weight, eat some protein, green vegetables, take vitamins/minerals and calcium, drink a lot of ice water, and exercise a lot...This is about the fastest you can go, maintaining protein intake and exercise may protect from some muscle wasting