The special drops used in together with decreased daily calorie intake constitute the HCG diet. On a low calorie diet, the body burns up the day's calorie intake faster and begins to burn fat as a source of fuel instead. The supplements used in the diet help to maintain muscle mass and burn only fat where a low-calorie diet alone would affect muscles before fat is used. The HCG drops used in the diet help to alleviate any ill effects normally associated with a low-calorie diet such as fatigue and irritability. While on the HCG diet, the body restructures the way it usually uses stored fat and regular calorie intake. There are three stages in the special diet beginning with the introduction phase, the training phase, and the continued maintenance phase.

In the beginning of the special diet, the first two days consist of an increased calorie intake along with initiation of HCG drops. The first stage of the diet helps to re-set the body's natural way of handling calorie intake and burning fat, which will be utilized in the low-calorie portion of the diet. The higher calorie intake at the beginning of the diet also helps to eliminate hunger during the low-calorie portion of the diet. During the second phase of the special diet, the body is beginning to use stored fat as fuel and the initiation of a low-calorie diet will help to ensure that it continues to do so.

The final phase of the diet, known as the maintenance stage, starts when the drops have successfully altered the body's metabolism. Calorie intake begins to increase back to normal levels, and the use of formula is no longer necessary in the maintenance stage of the special diet.

The body's new, rearranged fat-burning process should not be disrupted by higher calorie intake, and the increase should be done slowly. Weight must be monitored closely during this period to ensure that the results of the diet are maintained and the reintroduction of normal calorie intake is not inhibiting the metabolism's changed procedure.

With the low-calorie intake during the diet plan, only light exercise is recommended for the physical activity portion of the diet. Heavy exercise could cause fatigue and starvation as the body burns the few calories it has for energy faster. The hormones in the drops will not affect a woman's menstrual cycle, and there are no other known side effects from the program. Pregnant women are not advised to use the program, as they are likely to see little to no results because of higher calorie intakes necessary for nourishment during pregnancy.