Dr. Oz doesn’t know it but he’s responsible for a lot of the emails I get. For example, in a recent segment of the Dr Oz Show, an herb called Coleus forskohlii was said to be one of the secrets to weight loss. I first reviewed Coleus forskohlii in my book a few years ago, but in case you missed that chapter, let’s take a look at Coleus forskohlii (sometimes called Forskolin) and see if I can help you make sense of it.
What is Coleus forskohlii?
Coleus forskohlii, is a member of the mint family of herbs. Its technical name is Plectranthus barbatus. The roots of the plant contain a compound called forskolin. As such, coleus forskohlii and forskolin are often used interchangeably. Traditionally used in Ayurvedic medicine to treat asthma and other ailments, for the last several years, 
it’s the claims that forskolin helps weight loss that has sparked peoples interest the most. I’ve even seen Dr. Oz say “it works” when talking about forskoiln
Supplement Tip. There are many weight loss supplements that contain Coleus forskohlii. As a personal rule of thumb, any supplement that contains the prefix “fors” or forsk” (or something similar) in their name, probably contains coleus forskohlii.
Coleus Forskohlii and weight loss.
How does Coleus forskohlii help weight loss? Or rather, what is the theory behind how it’s supposed to work? This will get a little technical but bear with me, I promise to bring it home at the end.
Coleus forskohlii stimulates the production of a molecule called cyclic AMP (cAMP). In our body, cyclic AMP helps our cells talk to each other. When an increase or decrease in cAMP is detected, it acts as a signal that causes the body to do something. One of the things that cAMP does is tell our cells to increase in an enzyme called hormone sensitive lipase—which burns fat. cAMP might also seems to stimulate the release of thyroid hormone which also helps burn fat and calories.
Translation: Coleus forskohlii (Forskolin) stimulates fat-burning enzymes and hormones which, in turn, causes weight loss.
The theory sounds good but is there any proof? It turns out there are a couple of Coleus forskohlii weight loss studies. Let’s take a look at them now.
One study published in the Journal Obesity Research in 2005 looked at 30 overweight and obese men. Half of these men received Coleus forskohlii and half received a placebo. The people in this study took 250 mg of a supplement (ForsLean) that had 10 % Coleus forskohlii. They took the supplement twice a day. The study lasted 12 weeks.
Body fat was determined via DEXA, a very accurate body fat measurement technique that uses x rays. At the end of the study, those getting Coleus forskohlii showed a reduction in body fat as well as an increase in testosterone.
Lean body mass (I take this to mean muscle) increased as well– but lean body mass also increased in both the placebo group. While lean body mass did increase more in those getting the Coleus forskohlii extract, how did the placebo (which should do nothing) increase lean body mass? This is a problem. The people in this study did not exercise. So if exercise didn’t cause the increase in lean body mass what did?
Another problem is that the people in the Coleus forskohlii group had higher testosterone levels at the start of the study than those in the placebo group. If the people were randomly divided into two groups, one would think that testosterone levels would be pretty much the same between the groups. But they were not. This doesn’t make sense.
Another observation was that Coleus forskohlii did not appear to increase metabolic rate. This totally contracts “experts” on the Dr Oz Show who have said that forskolin raises metabolic rate.
This particular study gets mentioned a lot on bodybuilding websites, however given the problems I just listed, I’d like to see another study to confirm these findings.
In another study, published in 2005 in the International Journal of the Society of Sports Nutrition, , 19 women were either given a Coleus forskohlii supplement (ForsLean) which contained 250 mg of a 10% Coleus forskohlii extract. The supplement was taken twice a day. The other group received a placebo and the study lasted 12 weeks.
Body fat was determined via DEXA. This study found that Coleus forskohlii did not promote any significant weight loss but it did seem to reduce the gaining of weight.
The forskolin extract did not seem to change thyroid hormone, liver enzymes, cholesterol, insulin, heart rate, blood pressure or red or white blood cells. This study unfortunately did not measure testosterone. So, while the Coleus forskohlii extract didn’t seem to help weight loss, it did appear to help people from gaining weight.
It is interesting that supplement used in this study (ForsLean) is the same as that tested in the previous study. So, two studies on the same supplement each finding different outcomes.
As far as I could tell, these appear to the only recent human studies of Coleus forskohlii and weight loss. If these are the only two studies, then they appear to contradict each other in terms of whether Coleus forskohlii helps weight loss or not.
Based on this, maybe forskolin helps weight loss or maybe it might reduce the rate at which people gain weight. So which is it? I don’t think anyone has the answer at this time. This is a far cry from the proclamation of Dr Oz who said on his TV show it works.
Coleus forskohlii side effects.
Based on the human studies done so far, Coleus forskohlii seems to be pretty safe in healthy people for at least 3 months. There is no research on people who are not “healthy” and the herb may interact with medications like blood thinners. People with serious health issues like heart disease etc. should speak to their doctor before taking Coleus forskohlii.
Does it work or does it help you lose weight?
While you may have heard Dr. Oz say a weight loss supplement “works”, have you ever heard him say a supplement “causes weight loss”? I haven’t and this may be why:
Saying “it works” is vague language that gives the impression that something helps you lose weight. People connect the dots in their mind and assume that’s what it means.
In ads, this is a way of tap dancing around the law because if somebody really did say in an ad that “Coleus forskohlii helps people lose weight”, they would have to prove it. This is why ads for supplements always say “it works”.
So, the next time you hear Dr. Oz say “it works” in reference to some weight loss supplement, ask yourself why he’s not saying “it helps you lose weight”.
As I have tried to show, the research on forskolin is interesting but it is far from conclusive. If the research is to believed, there may be something to it but the best results so far only seem to be based on just one study, which I think is questionable.
What do you think?
{ 16 comments… read them below or add one }
I’m curious as to why the study groups in the two trials were separated out as males in the first, and females in the second?
I’m also wondering if the difference accounts for the two different outcomes.
I would also suspect that the first study was somehow biased–therefore the outcome was perhaps a bit pre-determined? In other words, rigged.
Frosty, While unconscious bias is always possible, I tend to give researchers the benefit of the doubt when it comes to “rigging” studies. I think most researchers really try to do the best job they can, but I also know that no study – even peer reviewed studies – are “perfect”.
I can tell you that the company that makes the supplement used in the studies -ForsLean – at least partially supported the study (donating product) but the researchers (in the 2nd study I reviewed if I remember) did stipulate they had no conflict of interest.
That said, the study which found forskolin raised testosterone etc. did look a little odd to me and why I’d like to see it duplicated by others.
I saw this show too and agree, that from what I read there was not a lot proof. Silly me, I bought it and then did the research. I have not been taking it because, I read about some side effects that were concerning and did not see and other benefits than perhaps not gaining as much were worth it. It seems odd the both this and the Sea berries both thin blood. I fell like the berries are worth a try because of the other benefits. Since they have omega 3 and A,C,E etc. in it I though I may be able to cut back or replace some supplements with the berries? What do you think?
Hi Claudia, the blood thinning effect is one of the most common potential side effects I see in supplements. I usually mention it because many so people take blood thinner meds and they need to know about this interaction.
when you say sea berries, did you mean sea buckthorn?
In general, I like getting nutrients from food because they have a more broad spectrum of nutrients. I all edible berries are good choices. I add berries -blueberries, strawberries etc to every smoothie I make with my Vitamix.
I saw that Dr. Oz show and purchased a bottle, but after I got home, I did some research and found that the side effects -potential stomach bleeding wouldn’t be worth it since I’ve had some stomach ulcers. I think it is irresponsible of Dr. Oz to promote this stuff without talking about side effects. I haven’t opened the bottle and still have the receipt and hope that Whole Foods gives me a refund.
I like the way you write… very down to earth and unbiased.
Leela, thanks for the compliment. I appreciate you saying that! I’m about to post a review on Raspberry ketones which Dr Oz called a weight loss “miracle”. It should be on my site soon.
I saw Dr. Oz’s show today. I went to check it out at the store and decided against it. Dr.Oz’s show is always trying to get you buy this, use that, I’m just not to sure about him any more.
Carey, I understand. I sometimes scratch my head over recommendations also.
Please note. The test was for 10% Coleus Forskohlii. Dr Oz mentioned it needed to be 20%. Anything less would not show the results people expected.
Sandy, you may be right – I may have missed him saying that – but I’d still be interested in knowing where Dr Oz came up with the “20% works” statistic.
My wife and I have been using a 10:1 Forskolii extract 250 mg a day. My wife noticed my stomach fat was reduced. I have been working out 4 times a week also. I have noticed and believe it has the desired effect on me.
I belive most licensed pysicians would not globaly “prescribe” a substance that had a significant effect on the human body. There might be liablity issue. I find Dr. Oz’s “Mr. Science” demonstrations insulting.
My first time on your sight. Think I’ll subscribe. Thank you for the blog.
Zede, Glad you found me and its a good point you make about globally prescribing things on TV.
Hi, Joe,
My husband bought a bottle right after the Dr. Oz show. He started taking Coleus Forskohlii right away. I am not a pill type person, so I have been waiting to see where this goes.
I think the old saying “If it sounds too good to be true, it probably is” applies here. My research did bring me to your blog though, so I am looking forward to future postings.
Joni
Very interesting site.
Hello…I too saw the show on Dr. Oz and of course went out and bought Forsaklin and the 7Keto. I have been taking it for the past 3 weeks and I don’t have time to exercise much, but I did lose 4 lbs. I don’t know if its the pills or not but I haven’t changed my diet at all.