In pregnant women, hCG causes the body to use up stored fat to provide food and nourishment for the fetus. The trait of prompting the body to consume old fat deposits is what makes it a dieting aid, which was popular in the 1950s and has resurfaced recently. However, those who want to lose weight should be aware that there are possible side effects and dangers to using hCG in this way.

Because hCG occurs naturally in pregnant women, without harming mother or fetus, it would seem to be safe. In fact, as a treatment, it is given in much smaller doses than those naturally occurring during pregnancy. However, the FDA has not given approval to hCG as a dieting formula. It is approved as a fertility treatment, so women who do not want to get pregnant should be particularly cautious about using hCG for weight loss.

Despite its lack of FDA approval for dieting, since the drug exists, there are doctors prepared to prescribe it for this purpose. Some Internet sites sell something purporting to be hCG without the need for a prescription, but you should be wary of such drugs as there is no control over their effectiveness or safety. Even with the prescription drug, there can occasionally be unwanted side effects when taking hCG. Headaches, depression and restlessness may occur, as well as an increased risk of blood clots developing in the body. Not entirely surprisingly, hCG users may feel some of the symptoms of pregnancy during treatment, such as water retention, swelling and sensitive breasts. In rare cases, hCG can cause ovarian hyperstimulation syndrome (OHSS), which may be fatal.

Treatment with hCG can be expensive and it’s not covered by health insurance. Some studies have shown that patients who consumed the same low-calorie diet (500 calories a day), but who were given a placebo instead of hCG did, just as well in terms of weight loss. And there's the perennial question: Will the weight stay off once the treatment has finished?