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MIAMI (CBSMiami) — What’s the slimming secret of celebrities these days? Hollywood is supposedly swearing by an all-natural, appetite suppressant.

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But could it really help you lose weight like a star?

“It’s the most popular weight-loss supplement worldwide right now,” said nutritionist Lauren Slayton.

It’s called Garcinia Cambogia.

“The claim is that the active ingredient decreases our appetite and decreases the amount of fat we store,” Slayton said.

The active ingredient is called hydroxycitric acid, also known as HCA, and the one-two punch it supposedly delivers has many people saying they’re effortlessly shedding the pounds. Some say they’ve lost as much as 20 pounds over a single month.

“I’ve been seeing a really big difference in the way clothes are fitting me,” one user said.

Another said they’ve lost 47 pounds. Others claim different benefits.

“I’ve been seeing more definition in the shoulders, the pectorals and the arms,” another said.

Manufactured by a variety of supplement companies and sold just about everywhere now in pill form, Garcinia Cambogia actually comes from a tropical fruit grown in Southeast Asia.

For best results, directions indicate to take three pills a day; one before breakfast, lunch and dinner.

“By the time we are ready for our meals, we don’t really feel very hungry,” a user said.

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But before you run out and buy a bottle, Slayton said the research on whether it actually works is mixed.

“There are some studies that show it’s more effective than a placebo, a couple of pounds,” she said.

But about half the studies show no results at all.

“And those are studies using an exact precise amount so it’s not necessarily effective,” Slayton said.

“You need to be really suspicious,” Tod Cooperman, of Consumer Lab, said.

Cooperman said his company tested 13 different Garcinia Cambogia products and that more than half barely contained any of the actual active ingredient.

“We don’t always know exactly what else is in there, probably just filler,” he said.

“Garcinia Cambogia, did it for about a week and gained weight people,” another review read.

Reported side effects include dizziness and nausea.

Experts say there really is no “magic pill” and that the best way to lose weight is through diet and exercises, but they do have some tips.

“What we suggest is matcha, which is a powder form of green tea and research shows it improves your metabolism and decreases your fat storage,” Slayton added.

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Several studies show matcha improves metabolism and decreases fat storage, something Slayton say has yet to be proven with Garcinia Cambogia.