In recent months Dr. Oz has touted raspberry ketones as a miracle fat-burner on his self-titled show. He explains it as a substance that "tricks your body into acting like it's thin" by increasing the levels of a hormone called adiponectin. Since this hormone is naturally expressed in higher levels in people who are naturally thin, Dr. Oz says that raspberry ketones can "help your body think it's thin".

What are they?
Ketone is the term used to refer to a particular chemical bond, and any molecule that contains that bond. A ketone bond is very reactive, which can allow the aromatization of a molecule containing it.

Aromatization means that we can sense the molecule as a smell. Raspberry ketones are a major aromatic compound in red raspberries, and thus they are responsible for the smell of raspberries. Because of this function, raspberry ketones have been used in cosmetics and perfumes as a scent since the 1960's. Naturally extracted raspberry ketones exist at about 1-4mg per kilogram of red raspberries. It would not be possible to eat enough raspberries to get a physiologically active dose. Because of this, naturally extracted raspberry ketones are extremely expensive, and so commercially available varieties are often synthesized in a lab.

Research On Weight Loss and Raspberry Ketones
Dr. Oz's advice is based on two research studies involving mice that were fed high fat diets and high doses of raspberry ketones (1-2% of food weight). These mice failed to gain as much weight as other mice on the same diet. When examined, it was found that the mice fed raspberry ketones had higher levels of the hormone adpionectin. Another study also found that raspberry ketones promoted the breakdown of fat inside the fat cells to increase weight loss of mice. Thus, raspberry ketones have been established as body-fat-reducing in mice.

Promising Research
The initial research on raspberry ketones appears very promising. Unfortunately, because there are no human studies, it is not possible to say that the effects in mice will also be seen in humans. Although mice are a good initial test group to examine a general idea of function and safety, they are genetically different from us and do not always react the same way humans do to the same substances. Further research using humans is required to know the safety and efficacy of raspberry ketones in humans.

How Fast Does Raspberry Ketone Work for Weight Loss?
On the show Dr. Oz explains that results can be seen in a few days, and will progressively increase over time. There are no research studies to back up his claim at this time. Dr. Oz also stressed that these are not "magic pills" and that raspberry ketones have to be combined with a healthy diet and exercise to produce significant weight loss.

Dosage
There is no established safe dose for this particular supplement. On Dr. Oz's show a dose of between 100 and 200mg at breakfast was recommended to help support weight loss when combined with diet and exercise. Despite the lack of research, because raspberry ketones are extracted from the fruit, they are generally considered safe.