The only reason people lose weight on that plan is you are only allowed to eat 500 calories a day. HCG has been scientifically proven to do NOTHING to help with weight loss or to make it safe to eat only 500 calories a day. It will not protect muscle, reset your metabolism or do anything else the snake oil salesmen that sell it claim. Dr. Simeons was a quack doctor. His "HCG protocol" has absolutely NO scientific backing and is not worth risking your health on.
The HCG diet has been studied by many scientific organizations, and they all concluded that HCG, even the "real" injectable version, is no more effective than a placebo, and eating only 500 calories a day for weeks, as recommended by that plan, can cause more health problems than it solves.
Please read the articles on these websites before you try HCG. I know some people that put their faith in the HCG diet, and became very ill from malnutrition as a result. Then they regained more weight than they lost. Now they wish they never heard of HCG.
The Government is now in the process of getting all that fraudulent stuff off the market, and it's about time!