Green Coffee Bean Extract is one of them.... it is currently among the world's most popular weight loss supplements.
As the name implies, this supplement is extracted from green coffee beans.
It contains a substance called Chlorogenic Acid, which is believed to be responsible for the weight loss effects.
Green coffee extract was promoted by Dr. Oz back in 2012. He is an American TV doctor and probably the most famous health "guru" in the world.
I'm a big fan of supplements in general, but I am extra skeptical when it comes to weight loss supplements because they almost never work as advertised.
This article takes a detailed look at Green Coffee Bean Extract... what it is, how it works and what the science has to say about it.
What are green coffee beans?
Green coffee beans are basically just unroasted coffee beans.
Coffee beans are naturally green, but they are usually roasted before being sold to the consumer. This is the process that turns them brown.
As we know... coffee beans are loaded with antioxidants and pharmacologically active compounds. Two of the most important ones are Caffeine and Chlorogenic Acid.
Chlorogenic Acid is believed to be the main active ingredient in green coffee beans. That is, the substances that produces the weight loss effects (1).
Unfortunately.... most of the chlorogenic acid is removed when coffee is roasted (2).
For this reason, regular coffee beans won't have the same effect (although there are plenty of other good reasons to drink coffee if you enjoy it).
Bottom Line: Green coffee beans are the same as regular coffee beans, except that they haven't been roasted yet. They are high in a substance called Chlorogenic Acid.
How does green coffee bean extract work... what is the mechanism?
Green coffee bean extract does contain some caffeine.
However, the main active ingredient is believed to be the chlorogenic acid.
If this is true, then taking green coffee bean extract would be like eating a slightly lower carbohydrate diet.
Other studies (in mice and rats) have shown that chlorogenic acid can reduce body weight, reduce fat absorbed from the diet, reduce fat stored in the liver and improve the function of the fat burning hormone adiponectin (7, 8).
Bottom Line: Green coffee has been shown to inhibit weight gain in animal studies. This may be due to decreased absorption of carbohydrates from the diet, or via some other mechanism.
What do the human studies say?
There have been several human studies on Green Coffee Bean Extract.
These studies are so-called randomized controlled trials, which are the gold standard of scientific experiments in humans.
One of them included 30 overweight individuals and went on for 12 weeks.
There were two groups... one consumed regular Instant coffee, while the other consumed Instant coffee enriched with 200 mg of Green Coffee Bean Extract (10).
Neither group was instructed to change their diet or exercise habits.
This graph shows the weight changes in the two groups, from 0-12 weeks:
As you can see, the group taking the instant coffee with green coffee bean extract lost 11.9 pounds (5.4 kg), while the group taking plain instant coffee lost only 3.7 pounds (1.7 kg).
Body fat percentage also went down by 3.6% in the green coffee extract group, compared to 0.7% in the other group.
Several other studies have reported significant weight loss in people taking green coffee bean extract (11).
However, it's important to keep in mind that some of these studies were sponsored by companies that profit from sales of green coffee beans.
This doesn't necessarily mean that the results are invalid, but it is known that the funding source of a study can have a significant effect on the outcome. For this reason, it is a good idea to be extra skeptical of industry funded research (12).
In 2011, a review of the evidence behind green coffee bean extract concluded (13):
"... the results from these trials are promising, but the studies are all of poor methodological quality. More rigorous trials are needed to assess the usefulness of GCE as a weight loss tool."
Bottom Line: Several controlled trials in humans show that green coffee bean extract can lead to significant weight loss. However, these studies were relatively small and some of them were industry sponsored.
Does green coffee extract have other health benefits?
Green coffee may positively affect how our bodies absorb and use carbohydrates.
As hypothesized in the animal studies, supplementing chlorogenic acid appears to reduce glucose absorption (14).
This effect on glucose metabolism could play a protective role in diabetes management, and may also explain the effects on body weight.
Green coffee extract may also positively affect blood vessels, which has major implications for heart health.
Chlorogenic acid also functions as an antioxidant (17).
Bottom Line: Green coffee bean extract may improve glucose metabolism and reduce blood pressure. This may have benefits for people who are at high risk of diabetes and heart disease.
Side effects, dosage and how to use it
According to the limited evidence available, green coffee bean extract appears to have a pretty good safety profile.
This study is too small to demonstrate that the side effects were caused by the supplement itself, it may just have been a coincidence.
Green coffee does contain caffeine, which can have numerous side effects when consumed in large amounts. This includes anxiety, jitteriness, rapid heartbeat, etc.
Green coffee has not been shown to be safe for pregnant or breastfeeding women and should not be consumed by children.
There is currently no study that determines an optimal dosage for green coffee bean extract. However, the studies in the article above used dosages ranging from 120-300 mg of Chlorogenic acid.
Depending on the concentration of Chlorogenic acid in your supplement, this can range from a dosage of 240-3000 mg of green coffee bean extract per day.
I recommend that you follow the dosage instructions on the bottle. A common recommendation is one serving, 30 minutes before each meal.
Take home message
Green coffee bean extract does appear to be useful as a weight loss aid. It may also have some benefits for glucose metabolism and blood pressure.
However... most of the studies are small, short-term and often sponsored by companies that produce or sell green coffee beans.
At the end of the day, the only thing that is proven to lead to long-term results is changing your diet.
In this regard, cutting carbs and eating more protein seem to be the most effective, as well as emphasizing real, unprocessed foods.
That being said... I suppose green coffee bean extract is worth trying out if you are curious about it.
It might have a mild effect that can last for a few weeks or months, but I wouldn't expect anything beyond that.
Losing weight is a marathon, not a sprint... and quick fixes never work in the long-term.