The theory is that this hormone helps to release excess fat from a woman's body during pregnancy to ensure that the developing baby always has adequate nutrition, even if the mother encounters a time period of scarce food. When this hormone is injected into dieters, it is also said to help dull their appetite and keep them from being hungry. How this would help a pregnant woman, I have no idea, but it could explain why many women end up losing weight during their first trimester or pregnancy instead of gaining it. On the other hand, it could be all of that vomiting from morning sickness. Who knows? The question is: Does this diet work?
The first fact that makes me doubt the efficiency of HCG in making a person lose weight is that many of the HCG diet plans specify that the person on the diet must eat 500 calories a day only. If HCG worked so well at dulling the appetite and making a person burn fat, why would they need to stick to such a strict diet plan? A person on a 500-calorie diet is sure to lose weight no matter what -- it is just a matter of physics. So, why prick your body with a needle every day injecting yourself with pregnant women's hormones if you are going to have to stick to a strict diet anyway?
In addition, many companies are now coming out with HCG diet drops, which are taken orally instead of through injection. Many of these drops have been proven to contain trace amounts of HCG, if any. If they work, it is because of the placebo effect. My advice is to stick to a healthy diet and exercise plan and forget about relying on HCG. It is expensive, has not been proven effective, and no one knows what the long-term effects are of injecting yourself with these hormones.