HCG Diet

It's illegal and unhealthy.

HCG diet is ridiculous. You have such a major deficit in calories you are going to lose weight (in unhealthy ways) whether you take the HCG or not. HCG is a pregnancy hormone not a weight loss miracle.

To answer you in a bit more detail:

HCG does not really do anything. HCG requires you to take hormones while maintaining a very low calorie diet (usually 500 cal/day. You will find people all over teh interwebz saying "I did HCG, it was great, the weight just fell off!" But in trials, people who ate a calorie-restricted diet and took HCG lost weight at the same rate as people who ate the same calorie-restricted diet and did not take HCG.

Furthermore, adhering to a calorie intake at that level can result in problems. When your caloric deficit is too high, your body cannibalizes muscle for fuel as well as that fat that you would like to eliminate. This causes problems in multiple ways. 1) Most importantly, some of the muscle cannibalized can come from internal organs such as your heart. 2) Losing enough muscle results in you burning significantly fewer calories than you would ordinarily burn at that weight. This frequently results in an extremely rapid weight regain, ending up at the same weight or heavier, with less muscle (so you look even fatter than you did before). 3) You frequently lack energy for even mundane tasks of daily life.

tl;dr summary: Don't do it.

500 calories a day plus hormone shots is incredibly unhealthy. The hormone shots are completely unnecessary because at 500 calories, you're going to lose weight regardless. But it's not going to be healthy weight loss, and keeping the weight off is completely unrealistic. With that drastic of a deficit the weight's going to come back the second you start eating normally again.