There are many dangers of implementing only 500 calorie diet as your body won’t be getting the necessary nutrients that can lead to any vital organ failure. Also, you will be feeling hungry and literally starving that can lead to irritative behavior, depression, overstress etc. ultimately leading to overeating (after you lose patience). Using hCG uses the bad fat on the body and converts them to energy while triggering the brain to think you are full. It also keeps you mood levels stagnant.
Hence, 500 calories should be accompanied by hCG drops/shots or pellets.