Is it true that it's ok to eat less than 1000 calories per day to lose weight?

Not long term: Also depends on what's in those calories. You need 13 essential vitamins, 15 essential minerals, essential fatty acids, essential amino acids, and water to survive. If your body gets what it needs, it doesn't need more. It's not wise or safe to get it from pills so make sure the foods you are eating contains the essentials. No carb is essential to human health because glucose comes from protein.