All you need to do is take her weight time 10. For a man I would take it by 12-15. This gives you a guides total of calories. For example, I am 212, x12 =appx 2500 cals, so that's how you would do your wifes total calories. Some say, if you want to get to 180 and you weigh 220, then you need to go half way and adjust after 200. This also depends on how long she can sustain with depleted calories.