Most fad diets promise quick weight loss, but are often unhealthy and don't work in the long-term. The latest diet craze, however, takes it to the extreme, and involves injecting the hormone hCG (human chorionic gonadotropin) while eating just 500 calories per day.

hCG was first pushed as a weight-loss aid in the 1970s. Fans of the diet believe that it could help people lose weight because in pregnant women, hCG helps to direct calories to the fetus.

hCG is a hormone first produced by the developing embryo, and then the placenta during  pregnancy. Promoters of the diet say that because hCG helps re-route calories from the mother to the fetus during pregnancy, injecting the hormone could help curb appetite and help dieters to get through the day on few calories. Dr. David Katz says:Beyond injecting the hormone, subsisting on just 500 calories per day is dangerous.

Restricting caloric intake to such a level makes for a real risk that you're not providing your body with enough essential amino acids, so it scavenges itself. Sometimes, it can cause the body to scavenge from critical places, like the heart. If you're looking to lose weight, for the sake of your health, avoid this diet.