The HCG diet drops coupled with the very low calorie diet allows abnormal fat deposits to be tapped into and released into the blood stream. This release of fat/calories into the blood stream is also why people taking the HCG are generally not hungry and generally have plenty of energy.
According to Dr. Simeons, the physician who developed the HCG diet plan, the HCG actually releases 1500-4000 calories per day into the bloodstream. This is the only reason why it is okay to eat based on a 500 calorie diet.
Without the effect of HCG, Dr. Simeons and the rest of the world agreed that a typical very low calorie diet leaves the dieter looking haggard (with a skeleton-like face), starving, and facing excess nutritional deficiency. Most diets begin weight loss by depleting your structural fat (that fat which cushions your organs and gives your face a soft, non-skeletal look) and your normal fat reserves.
However, MOST diets are slow to affect the abnormal fat which is stored in your abnormal fat deposits (shoulders, upper arms, hips, thighs, and buttocks), which seem to have only one efficient key to unlock them: HCG.
Dr. Simeons described the process as tapping into the abnormal fat deposits, and further proposed that HCG potentially affects your hypothalamus and your base metabolism.
The HCG diet protocol inherently is an effective detox because only a small amount of food is eaten each day and all of the food should be quite healthy. This alone gives your entire system rest from the onslaught of unhealthy, processed foods and drinks people typically take in. Some experts feel this detox allows your hypothalamus to clear itself of the chemical build-up that could be preventing weight loss and re-establishes the natural functioning hormone release of the hypothalamus.
So, again, unlike MOST diets, the HCG diet plan potentially has long-lasting effects that help change your attitude towards food and may help your body handle that food more efficiently.