After the May airing, sales of the product -- which is made from an extract of raw, unroasted coffee beans -- skyrocketed.
The dream of losing weight by popping a pill isn't going anywhere. The green coffee bean extract mentioned on Oz's program and another compound found in raspberries called ketone are the latest products aimed at people trying to shed extra pounds.
Oz called green coffee bean extract "one of the most important discoveries we've made to help you burn fat faster."
Do they actually work?
Here's the claim: Green coffee bean extract contains a compound called chlorogenic acid that inhibits the release of glucose in the body and increases the metabolic process in the liver.
Chlorogenic acid is removed during the coffee bean roasting process.
Raspberry ketone is an aromatic compound found in raspberries and other fruits.
In one experiment, researchers fed a high-fat diet plus raspberry ketone to rodents for 10 weeks. Researchers observed that the ketone decreased the amount of fat in the liver and rodents' abdomens. It also increased the decomposition of fat in some cells.
The most cited study on green coffee extract was published in the January issue of Diabetes Metabolic Syndrome and Obesity Journal.
Researchers tracked 16 overweight adults who took a green coffee bean extract of chlorogenic acids for 12 weeks. The subjects lost an average of almost 18 pounds without making any significant changes to diet.
After Oz was criticized for his "miracle" comment, he followed up with his own study and found that after two weeks, the 50 women he tested using the supplement lost about 2 pounds, double the amount of weight lost by the other half of the group taking a placebo. All the women were asked to keep a food log but make no other dietary or lifestyle changes.
There isn't enough research yet on either product to know for sure if these supplements are effective, said Paula Hanes, a registered dietitian with Providence Regional Medical Center Everett.
"There's no hard scientific evidence proving it works," she said.
The results would need to be repeated many times on a wide cross-section of people before it's clear if the extract works, Hanes said.
The study that got Oz and everybody else buzzing about green coffee bean extract tracked just 16 people.
Researchers have tested the effects of raspberry ketone only on animals.
She noted the ketone used in both experiments and sold as a supplement are a synthetic product -- not a natural one as some sellers claim -- since it would take many pounds of raspberries to produce a single pill.
That said, Hanes said that unless you're allergic to coffee, the green coffee bean extract is probably relatively safe for healthy adults. The raspberry ketone's long-term effects are unknown since it hasn't been studied in humans.
Oz warned that many of the green coffee bean supplements available online are phony or ineffective. He does not endorse any particular brand.
If you want to try this fad, he suggested buying a supplement with at least 45 percent chlorogenic acid, which can also be listed on the bottle as GCA or Svetol.
His recommended dosage is 400mg three times a day, 30 minutes before each meal.
He suggested that pregnant and breastfeeding women and people under 18 avoid the supplement, since it hasn't been fully tested.
Bottles of 60 capsules of the green coffee bean extract were selling for as much as $39.95 on the Internet. The same size bottle of raspberry ketone cost $29.95.
Hanes, who has been a nutritionist for 13 years, recommended skipping the expensive supplements and instead focusing on what's proven to work: moving more and eating less.
The patients she has seen who have successfully lost weight over the long term have eaten smaller portion sizes, made better food choices and exercised.
"Weight loss is simple," she said. "But it's not easy."
If you don't know where to start, she suggested supportive programs, such as Weight Watchers, that don't require you to buy special food.
She also offered this final piece of advice: "If it sounds too good to be true, it probably is."
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