'Miracle' Diet Supplement Too Good to Be True?

"Yacon" syrup is believed to speed up metabolism, but there's little scientific evidence it helps you lose weight.
3:35 | 05/28/14

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Transcript for 'Miracle' Diet Supplement Too Good to Be True?
What's being called the next big thing in weight loss. It's called yacon syrup, helping to speed up your metabolism. But there are questions about it. Rebecca Jarvis explains. Reporter: It's the buzzing weight loss supplement, that has Dr. Oz raving. It's a natural food that you can eat every day. It's called yacon syrup. Reporter: And people on youtube, singing its praises. It is fantastic. The weightñr started to comeñr off. Reporter: What is yacon. And what is it supposed to do? It's a soluble fiber that helps us to fill full. And it contributes very few calories because it passes through our body undigested. Reporter: The syrupy substance looks like molasses. Tastes a little sweet, like maple syrup. And comes from this plant in south America. There it is. Direct from the source. Reporter: So far, few have actually studied its effects. And there's little scientific evidence it helps you lose weight. According to one study, overweight women taking three to four teaspoons a day for four months, dropped an average of 33 pounds. Four inches from their waist. With a few unpleasant side effects. Bloating, gastrointestinal distress, cramping. Reporter: Before you race out to get your yacon syrup fix, consider this -- The reality is, we have to eat healthier. We have to eat less. And we have to move more. That's what it comes down to. Reporter: For "Good morning America," Rebecca Jarvis, ABC news, New York. All right. So, joining us for a reality check is ABC's chief health and medical editor, Dr. Richard Besser. And reality check, indeed. You were telling me offcamera, there's some side effects. This is one where we need a reality check. There's only one study. It was done five years ago. But here's the catch. To get in the study, you had to be overweight and constipated. And there's a reason for that. This is concentrated fiber. We know whatçó fiber does when you take a lot of it. One-third of the people in the study dropped out because of the intestinal side effects. Because of the side effects. Is it actually safe? It's one study done five years ago. I always worry when there's something that looks promising and no one's looked at it since then, that there's something going on. It lasted four months. We don't know if this works long-term. I'd be concerned about taking this stuff for a long-term. The other big question. Every time one of these crazes comes up, we ask the question, is there a quick fix to a problem like this, being overweight? Or just struggling with weight? It's so hard. There's so many people that need to lose weight for their health. But you can't keep doing what you're doing now, in terms of what you're eating and how you're moving and expect there to be a change. But the idea there's something you can take that's going to answer all those questions is really enticing. There's a lot of money to be made off of weight loss products. And so, you're going to see stuff like this come up and again. There's stuff to take for constipation. Well -- Right. But it's not being put forward that way. And that's the danger here. It's being touted as, sort of a quick fix. Exactly. Exactly. And this is one that I would not recommend. There you go. Thank you. We're going to get to more

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