If you want to use Garcinia cambogia extract to help with weight loss, the first and probably most important thing I can tell you is that it doesn’t work anything like as well as it’s supposed to.
That’s not to say it has no physiological effect whatsoever. But if you’re expecting it to have a dramatic impact on the way you look, chances are you’re going to be disappointed with the results.
You’ll see Garcinia cambogia extract referred to as hydroxycitric acid, HCA or Citrimax. It’s a supplement derived from the fruit rinds of an Indian plant called Garcinia cambogia, which is used in Asian cuisine to make meals more filling. There are three main ways in which it’s supposed to work.
The first is by limiting the amount of carbohydrate that your body turns into fat.
When you eat a meal containing carbohydrate, it eventually ends up in your bloodstream in the form of glucose. If it’s not used for energy right away, your body stores it in your muscles or liver in the form of glycogen.
If your glycogen stores are full and you keep on eating a high-carbohydrate diet, your body needs somewhere to put it. And that’s where the problems start. When your muscles and liver are full, excess carbohydrate ends up being turned into fat.
The good news is that Garcinia cambogia extract has been shown to limit the conversion of carbohydrate to fat in subjects eating a high-carbohydrate high-calorie diet for seven days.
But that’s only half the story. While carbohydrate can be converted directly into fat, a process known as de novo lipogenesis (or DNL for short), this doesn’t happen unless you’re eating a lot of it.
In short, DNL isn’t something that you need to worry about unless you’re eating a high-calorie diet containing large amounts of carbohydrate. Which is the exact opposite of what you should be doing if you’re trying to lose weight.
Instead, one of the main effects of overfeeding with carbohydrate is that it replaces fat as a source of energy. By suppressing fat burning, the fat in your diet is far more likely to end up being stored.
Garcinia cambogia extract might be able to slow the rate of DNL. But it won’t stop it completely. Eat too much carbohydrate and, Garcinia cambogia or no Garcinia cambogia, you’ll end up gaining fat.
Not only is Garcinia cambogia supposed to inhibit the formation of fat, some say that it increases the amount of fat you burn.
It’s supposed to do this by reducing cell levels of malonyl-CoA, an enzyme that slows the rate at which fat is oxidized. This, in theory at least, would lead to an increase in the amount of fat you burn.
Putting the theory to the test, a team of scientists from Maastricht University put a group of ten cyclists through two trials, both of which involved two hours of cycling.
During the first trial, the cyclists consumed a drink containing 18 grams of Garcinia cambogia extract (HCA). In trial two, they were given plain water.
When they used HCA, the cyclists burned an average of 0.7 grams of fat per minute of exercise. When they weren’t given HCA, the cyclists also burned an average of 0.7 grams of fat per minute of exercise.
So despite the massive dose of HCA, it had no effect on the amount of fat burned during exercise. This is pretty much in line with other research showing that HCA (3 grams daily) has no effect on fat oxidation at rest or during exercise.
There are also claims that Garcinia Cambogia increases glycogen storage in the liver, leading to a sensation of fullness and a reduced appetite.
In one trial, HCA (300 milligrams three times daily) was shown to reduce 24-hour food intake in obese subjects by 15-30% with no increase in hunger.
Conversely, a three-month study of 89 overweight females at Purdue University shows that 1.2 grams of HCA daily had no effect on appetite.
A later study shows that high doses of HCA (2.8 grams per day) did lead to a faster rate of weight loss, mainly by suppressing the appetite and reducing calorie intake.
However, the fact that two of the study authors were involved with the company who make the supplement, but for some “mysterious reason” forgot to mention this in the research paper, does mean that we need to treat the results with some caution.
Most of the higher quality research shows that HCA fails to produce significant weight loss beyond that seen with a placebo.
Probably the largest and most rigorous study on HCA and weight loss was published in the Journal of the American Medical Association.
Subjects received either Garcinia cambogia extract (1500 milligrams of HCA per day) or placebo for 12 weeks. The average change in weight in both study groups is shown in the figure below
Although participants in both groups lost weight, there was no significant difference in weight loss between the two groups, which averaged 9 pounds in the placebo group and 7 pounds in the HCA group.
Researchers from the University of Exeter have also published something called a systematic review on the effectiveness of Garcinia cambogia extract as a weight loss supplement.
A systematic review is simply a way of summarizing research evidence. Systematic reviews are important because, rather than just cherry-picking research that supports your existing beliefs and ignoring everything else, you have a clear and transparent search strategy for finding data, you measure the quality of each study (ideally without knowing the results), and then present a balanced and impartial summary of the findings.
Here’s their conclusion:
“The evidence suggests that Garcinia cambogia extract/HCA generates weight loss on the short term. However, the magnitude of this effect is small, is no longer statistically significant when only rigorous randomized controlled trials are considered, and its clinical relevance seems questionable.”
Or to put it another way, when you strip out the low-quality studies, the research that’s left provides little in the way of compelling evidence to suggest that it’s worth spending your money on.
There are so many supplements out there promising to help you lose weight. But if they’re really so good, why do supplement companies keep coming up with new ones?
Think about it. If raspberry ketones, green coffee bean extract, HCA or whatever else is on the Doctor Oz show this week actually worked as well as it’s supposed to, there would be no demand for another one.
There might be a small benefit in terms of appetite control with higher doses of HCA. But having looked through the research, as well as having tried it myself on several occasions, it’s not a supplement I would recommend using.
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About Christian Finn
Christian Finn holds a master's degree in exercise science, is a certified personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Muscle & Fitness, Fit Pro, Zest and other popular fitness magazines.
