The Land of Oz
A Dr. Oz episode on the “Rapid Belly Melt” aired a month ago, on May 5. He set fire to a paper representation of a fat belly to show how forskolin “works like a furnace inside your body.” The paper ignited, went up in flames, and revealed a non-flammable model of muscle tissue inside to show how forskolin burns fat, not muscle, and to illustrate how quickly it works.
In an earlier episode, in January, he called forskolin “lightning in a bottle,” and a “miracle flower to fight fat.” His guest, a weight loss expert, claimed it had doubled the weight loss of her clients. She said “if your metabolism is sleeping, forskolin is gonna wake it up.” She doesn’t claim that it will work miracles all by itself, but recommends it as an addition to gentle exercise and “cleaning up the diet”.
Dr. Oz says he pulled up all the research and was impressed by the evidence that it “ignites your metabolism.” He illustrates this metaphorically by throwing a white powder into a pot of simmering water, causing it to instantly start boiling vigorously.
The Land of Evidence
Dr. Oz is easy to impress. He cites a randomized placebo-controlled double blind trial of forskolin. It was a small preliminary study of obese or overweight men; there were only 15 men in each group, and the study lasted for 12 weeks. The subjects on forskolin showed favorable changes in body composition: a significant decrease in body fat percentage and fat mass, with a trend (non-significant) toward increased bone mass and lean body mass. Serum free testosterone levels were also significantly increased.
The details of the study are not important. What’s important is that the subjects taking forskolin did not lose weight. Even without weight loss, the changes in body composition are likely beneficial, but the increase in testosterone could be dangerous. Whatever the unresolved questions about benefits and risks, it is obviously misleading to cite this study as evidence that forskolin has been proven to melt belly fat or improve weight loss.
Another double blind study of 23 mildly overweight women, showed that forskolin had no significant effects on body composition and concluded that it “does not appear to promote weight loss but may help mitigate weight gain in overweight females with apparently no clinical significant side effects.”
Those are the only two studies in humans. Supplement Geek has written an analysis of some of the flaws in those studies that I won’t get into here. The only other pertinent research I could find was a study in rats suggesting that it may be effective in preventing diet-induced obesity. In rats.
What is it?
Forskolin is an herbal extract from Coleus forskohlii, a plant belonging to the mint family. Its mechanism of action? It increases the production of cyclic AMP, which increases the contractility of heart muscle. Evidence for other actions is preliminary and inconclusive: there is speculation that it may have effects in other cells of the body such as platelet and thyroid cells, it may prevent platelet aggregation and adhesions, and it might even prevent tumor cell growth and cancer metastasis. So far, there is no evidence that it is clinically useful or safe for those purposes.
The Natural Medicines Comprehensive Database rates forskolin as “possibly effective” as an inhaled powder for asthma, and as an intravenous medication for idiopathic congestive cardiomyopathy. It also mentions that it may decrease intraocular pressure but has not been tested in patients with glaucoma. It doesn’t even mention the possibility of using it for weight loss. The safety rating is “possibly safe,” and it lists potential interactions with prescription drugs and with other herbs and supplements. They say it may increase the risk of bleeding and should be discontinued at least 2 weeks before surgery.
The bottom line
So what do we know?
- There is a more-or-less plausible mechanism of action, as speculated by the study authors (see the study for details).
- It improved body composition in one study but not in another.
- It has not been demonstrated to cause weight loss, except possibly in rodents.
- Its clinical efficacy and safety have not been established.
- It raises blood levels of testosterone, probably not a good thing.
I am not saying it doesn’t work for weight loss or belly melting; we don’t have good enough evidence to know whether it does or not. I’m not saying people shouldn’t take it, although they shouldn’t assume it’s perfectly safe. I’m only saying there is inadequate evidence for anyone to make the claims Dr. Oz and other proponents have made for it. If we had such limited evidence for a proposed new prescription drug, I doubt if Dr. Oz would want the FDA to approve it for marketing. The double standard is obvious.
Déjà vu all over again
I’m getting really tired of these weight-loss products, ever since I wrote about Akavar 20/50 “Eat all you want and still lose weight!” back in January 2008. I get a strong stink of déjà vu, because they all fit the same pattern: a small grain of plausibility, inadequate research, exaggerated claims, and commercial exploitation. There are always testimonials from people who lost weight, probably because their will to believe in the product encouraged them to try harder to eat less and exercise. But enthusiasms and fads don’t last. A year later, the same people are likely to be on a new bandwagon for a different product. Dr. Oz will never lack for new ideas to bolster his ratings. Enthusiasm for easy solutions and for the next new hope will never flag as long as humans remain human. I guess I’ll just have to keep doing the Sisyphus thing and hope that I can at least help a few people learn to be more skeptical and to question what the evidence really shows.
This article was originally published in the Science- Based Medicine Blog.