You can't sustain any weight loss no matter how little for the simple mathematical reason that body weight is nonnegative. I do agree that 2 lbs/week which is about 8000 calories, or about 3-4 days worth of calories, is a lot. For an average weight person. If you weigh a lot then it may be ok because you naturally burn more calories per day so 8000 calories may only be 2-3 days worth. You shouldn't look at the lbs/week figure but at how many percent fewer calories you're consuming than you need to sustain body weight.