"Is 500 to 1000 calories to little to have to eat?"
First off, yes eating five hundred to one thousand calories a day is to little. That leaves you short at minimum from about seven to one thousand calories a day. Also with such a low intake of calories, you will start developing deficiencies in certain essential micronutrients. Next is the fact that the caloric intake is in the range of that which those with or are in the process of developing anorexia will eat or try to erat below. On average for weight loss it's recommended to NOT drop below fifteen hundred calories, unless you're under the guidance of a doctor and a registered medical dietician.
If you need to lose weight, do it sensibly, and slowly. You don't want to lose it fast, as when you go back to normal eating, your body will start to slowly add the weight back on, plus additional weight above what was lost. Proper weight loss is done both slowly and with an increase of physical activity. Now in truth you don't need to lose any weight, as your BMI is well within the healthy range. If anything, you may want to eat a reasonable diet, adding in some exercise, to help lose any unwanted fat, which will be slow, while adding some healthy muscle mass.