Not everyone can sustain a 1500 calorie/day diet; you may need more or less, depending on your current weight
level. The types of calories you eat will have an impact as well. Yes, I know a calorie is a calorie; however if you eat foods with, say, a lot of sugar or other simple carbs, you blood sugar will not be stable and that sugar is likely to turn to fat, much more quickly than lean protein and complex carbs (whole grains, nuts, seeds, etc.).