HOUSTON --For many, it's a New Year's resolution to lose weight. But now a diet popular 50 years ago is making a comeback. And it's based on a few drops or pills containing HCG. Jennifer Nelson is on the HCG diet. "I've lost five pounds and one inch so far... in a week," said Nelson. Carolyn Holloway went on an HCG diet before Thanksgiving. "I lost 12 pounds.... in 26 days," said Holloway. "Put six drops under your tongue six times a day and hold them there for 30 seconds and then don't eat or drink for 15 minutes afterwards." Kymberly Rawls lost inches in her stomach on an HCG diet and says she's keeping them off. "I did this for 40 days and I lost 30 pounds in 40 days," Rawls said. "It was amazing. Just before my eyes it was melting away it seemed." So what is it? HCG stands for human chorionic gonadotropin. "HCG is a hormone found in the placenta of pregnant women," said Carole ut health dietitian It's a fertility drug, but not FDA approved for weight loss. Yet HCG diets have been around for 50 years. The new HCG diet combines drops or pills taken before meals with a diet that limits you to 500 calories a day. "But you're eating five times a day, so you don't get real hungry," Nelson said. "For me it was fine. It wasn't bad for me," said Holloway. UT Bariatric Surgeon Dr. Erik Wilson says 500 calories a day is a starvation diet. You'd lose weight, even without HCG. "The question about HCG is does it take away your hunger? That's the theory behind it, but clinical studies haven't really shown that," said Dr. Wilson. "I actually called my doctor to get her blessing before I did it," Nelson said. But she acknowledged her doctor didn't know much about it. Dr. Wilson, who does research on obesity, is concerned about side effects. "We don't fully understand how it works in non-pregnant patients. It does have some potential risks. You could get a blood clot, you have to understand that," Dr. Wilson said. When the HCG drops run out after 23 or 40 days, many continue the healthy eating. "It has changed my life. I am eating more protein and vegetables than I had before and trying to stay away from the bad stuff," Rawls said. And that may be the true key to their success. There were a lot of questions from our Facebook friends in today's chat about the HCG diet. Many asked how much it costs. Most of the people we talked with bought the HCG drops or pills over the internet for under $100.