DO NOT TELL YOUNG TEENS TO EAT ONLY 500-1000 CALORIES A DAY TO LOSE WEIGHT! Talk about a major malfunction! Eating such a small amount of calories slows down your metabolism. When your body only gets a few hundred calories a day, you "trick" it into thinking that food is scarce, so it starts to store up fat to be used as energy. So, before you go around telling 11 year olds to only eat 500 calories, do us all a favor and check the facts.