People are raving about yacon, a weight-loss supplement that even has Dr. Mehmet Oz singing its praises.

"It's not a pill. It's a natural food you can eat every day. It's called Yacon Syrup," Dr. Oz said on his show.

So what exactly is yacon and what is it supposed to do?

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Yacon is a South American plant that grows high in the Andes mountains of South America. Syrup extracted from the root of the yacon looks like molasses and tastes a bit like sweet maple syrup.

The root is a soluble fiber that helps people feel full, New York nutritionist Lisa Drayer said, adding that yacon contributes few calories because it passes through the body undigested.

The primary ingredient leading to weight loss, FOS (fructooligosaccharides), is also found in onions, garlic, asparagus, bananas, artichokes and chicory, but the concentration in yacon is much higher.

Few people have actually studied its effects and there is little scientific evidence it helps you lose weight.

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A 2009 study found that 55 overweight women who took 3 to 4 teaspoons a day for four months dropped, on average, 33 pounds and four inches from their waist.

Dr. Keith Ayoob, a pediatric nutritionist and registered dietician in New York, said yacon is not "a magic pill."

"People lose weight likely due to intake of calories. Pounds don't just melt away; it's because you consumer fewer calories," he said. "If this syrup helps people consume less, that's great. Beans have a lot of FOS, which have the same effect such as lowering your bad cholesterol."

He pointed out that the people in the study lost weight for a short time.

"It's easy to produce weight loss for four to six months but what's interesting is in 12 to 24 months, if the people kept the weight loss," he said.

Nutritionist Drayer says yacon syrup can have a few unpleasant side effects, including bloating, gastrointestinal distress and cramping.

For people considering yacon syrup for weight loss, Drayer offered this advice: "What we don't know from the studies is whether is yacon directly causes weight loss or if it's the placebo effect.

"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."