The Food and Drug Administration is cracking down on the "HCG" diet.
"There are no HCG products approved for weight loss, but there are many illegal HCG products for sale," says Elizabeth Miller, a pharmacist with the FDA.
She appears in a new video for consumers called "HCG: Dangerous to Dieters.'
The FDA has sent warning letters to several manufacturers of homeopathic HCG products sold in stores and online.
Consumers are being advised to stop using these products, and not to follow dieting instructions that call for 500 calories a day.
The agency warns very low calorie diets can increase the risk of gallstones, electrolyte imbalance and irregular heartbeats.
No one is regulating these homeopathic products and what they do or do not contain.
"I don't know what they're getting," said Dr. I. Anthony Cardella.
He runs a Miami wellness center with an HCG diet program.
However, he uses the kind that's available by prescription only and is FDA approved for female fertility and some hormone disorders in men.
HCG is a hormone produced in the body of pregnant women.
Weight loss patients at the Cardella Wellness Center get daily injections of medical grade HCG.
They are closely supervised and seen once a week, according to Cardella, who also puts them on 500 to 800 calories a day.
"If you took a study and took a patient and put them on no medication at all with 500 calories they'll lose weight, but the thermogenic effects of HCG will make them lose weight even more," Cardella said.
Cardella also said "it causes heat in the body and destroys fatty cells."
FDA labeling for the approved HCG drug products requires this statement:
"There is no substantial evidence that it increases weight loss beyond that resulting from caloric restriction, that it causes a more attractive or 'normal' distribution of fat, or that it decreases the hunger and discomfort associated with calorie-restricted diets."
Cardella says he tried HCG himself before using it on his patients and lost weight.
Also, none of his patients has suffered an problems related to his diet program.
FDA has received reports of serious adverse vents associated with the use of HCG injections for weight loss including clots in the lungs, depression, cardiac arrest and death.