HCG (human chorionic gonadotropin) weight loss program is a protein-based hormone diet with daily HCG injections and drastic calorie reduction. Proponents of HCG helps boost metabolism and lose a large amount of fat. The diet begins with the "loading phase" eating plenty of high fat and high calorie foods for two days. The "weight loss phase" limits your diet to 500 calories per day. Depending on your total weight loss goal, there are two treatment programs to choose from, 23 day or 40 day program.