CLEVELAND -- When Cleveland's own Dr. Oz featured it on his talk show last year, he declared, "I've got the number one miracle in a bottle to burn your fat. It's raspberry ketone."
And so launched a weight loss craze that had stores, barely being able to keep up with demand.
Raspberry ketone is a compound that gives raspberries their aroma. A Japanese study found high doses of it helped to prevent mice from gaining weight. And early studies found that it was non-toxic in rats, and had no side effects.
Just one problem.
"There have been no studies in humans directly linking raspberry ketones and weight loss," said Jan Friswold, a registered dietician for University Hospitals Case Medical Center.
Friswold is quick to point out that effects on mice don't always replicate in the complex human system. So she urges caution.
"There's no safety valve here. We don't know what's safe. It's not a good idea," she said.
Instead, she says, the secret to weight loss success is all about a healthy diet and exercise.
"I always tell my patients, 'Let's start with something small. Some small changes that you can do.'"
Despite an estimated $60 billion weight loss industry, obesity rates in the U.S. are at an all-time high.
Nutritionists like Friswold say it's proof: "There's no miracle cure for weight loss."