Animal Researchf-sugars-into-fats">Block conversion of sugars into fats>Garcinia cambogia may promote fat loss, but scientific evidence is inconclusive.
Garcinia cambogia is a tropical fruit native to India and Southeast Asia. The fruit’s thick yellow rind supplies an active ingredient called hydroxycitric acid (HCA), which may help with weight loss through:
- Inhibitting lipogenesis. HCA is suggested to block ATP citrate lyase, an enzyme required for converting carbs into fatty acids.
- Increasing fat oxidation during exercise, potentially promoting healthy weight management.
Garcinia cambogia is a pumpkin-like fruit native to India and Southeast Asia that has historically been used as food and wellness herb. Among its many purported benefits, Garcinia cambogia is perhaps most popular for its inclusion in weight loss supplements thanks to its hydroxycitric acid (HCA) content.
HCA was first identified in 1969 as an inhibitor of the enzyme ATP citrate lyase, which is an essential to the the conversion of carbohydrates into fats.1
The weight loss effects of HCA have been well documented in animal studies. Despite this, most human trials show that HCA found in Garcinia cambogia extract possesses limited and unreliable weight loss effects.
How Garcinia Cambogia May Help With Fat LossBlock conversion of sugars into fats
According to numerous animal studies, HCA blocks the conversion of carbohydrates into fats, a process called de novo lipogenesis. HCA achieves this by inhibiting the enzyme known as adenosine triphosphate citrate lyase (ATP citrate lyase).2 However, this process does not make a significant contribution to body fat in humans, which might explain why animal studies show far more impressive weight loss.
Potential decrease of appetiteeral animal and test tube studies have shown that the HCA content of Garcinia cambogia helps increase serotonin levels, which is a brain chemical responsible for regulating eating behavior and appetite. 3Other studies show that Garcinia cambogia extract also displayed activities similar to leptin, which is known as the “satiety hormone” because it helps inhibit hunger.4
Despite this, thus far human studies have failed to reproduce these appetite-suppressing activities. As such, they remain largely theoretical and may be restricted to animals.5
rong>Garcinia cambogia is a popular weight loss supplement ingredient. Indeed, it was originally considered yet another miracle weight-loss drug promoted by Dr. Oz. However, it has failed to live up to the hype, since its weight loss effects are weak at best and non-existent at worst.
Garcinia Cambogia’s Fat Loss Reputation
As one recent review paper summarizes, ” the evidence from RCTs [randomized controlled trials] suggests that Garcinia extracts/HCA generate weight loss on the short term. However, the magnitude of this effect is small, is no longer statistically significant when only rigorous RCTs are considered, and its clinical relevance seems questionable.”6
Animal studies of garcinia cambogia extract and HCA as a weight loss agent were successful enough to inspire a large number of human trials.
In this study, researchers fed 24 male rats with a restrictive diet for 10 days, followed by a high-glucose diet supplemented with HCA for six days. Both respiration quotient and energy expenditure decreased during the first two days of supplementation, indicative of a decrease in fatty acid synthesis. HCA also suppressed food intake during the first three days.
- The researchers concluded that “These results indicate that, in this animal model, HCA suppresses de novo lipogenesis. Moreover, HCA may improve glucose tolerance” 9
The researchers divided 36 obesity-prone male mice into three groups, with the first being fed a normal diet, the second a high-fat diet, and the third group a high-fat diet along with Garcinia cambogia extract.
At the end of the experiment, the third group had lower body weight gain, abdominal fat accumulation, and lipid and insulin levels than the other groups. Furthermore, the extract reversed adipose (fat) related genetic changes induced by a high-fat diet.
- The study concluded that “the Garcinia cambogia extract ameliorated HFD-induced obesity, probably by modulating multiple genes associated with adipogenesis” 10
Human Researche animal research, human trials of garcinia cambogia show mixed results. Even in the positive studies, the weight loss effect was relatively minor and has only been tested in the short-term.
In this influential, randomized, double-blind trial, 135 overweight people took either HCA (1500 mg) or placebo daily for 12 weeks while following a high-fiber, low-energy diet. Although both groups lost weight by the end of the study, there was no significant difference between them.
- The researchers concluded that “Garcinia cambogia failed to produce significant weight loss and fat mass loss beyond that observed with placebo“11
This randomized, double-blind, crossover study tested the hypothesis that HCA might promote weight loss by affecting energy expenditure (EE) and fat oxidation in 10 men. The men were given placebo or HCA (3 g) daily for 3 days, and had their EE and fat oxidation tested with or without 45 min of aerobic exercise. The study found no significant differences between placebo or HCA in either case.
- The researchers concluded that “These results do not support the hypothesis that (-)-HCA alters the short-term rate of fat oxidation in the fasting state during rest or moderate exercise“12
In this randomized, double-blind study, 44 people were treated with Garcinia cambogia extract (1000 mg HCA) or placebo daily for 12 weeks. At the end of the study, the Garcinia group saw significant reductions in body fat compared to placebo.
- The researchers concluded that “G cambogia reduced abdominal fat accumulation in subjects, regardless of sex, who had the visceral fat accumulation type of obesity“13
For this randomized, double-blind clinical trial, 60 moderately obese subjects were divided into three groups. The first was given hydroxycitric acid (HCA 4667 mg) before meals, the second was given HCA (4667 mg) plus niacin-bound chromium (NBC) and gymnema sylvestre extract (GSE), while the third group received placebo.
After eight weeks of treatment, both HCA groups had a significant reduction in body weight, BMI, food intake, total cholesterol, low-density lipoproteins, triglycerides, and serum leptin levels compared to the 3rd group. However, the effects were more pronounced among the second group participants.
- The researchers concluded that “optimal doses of HCA-SX and, to a greater degree, the combination of HCA-SX, NBC, and GSE can serve as an effective and safe weight loss formula that can facilitate a reduction in excess body weight and BMI, while promoting healthy blood lipid levels” 14
In this double-blind trial, six untrained men were given 500 mg of HCA or a placebo for five days and underwent moderate endurance exercise. The results showed an increase in the free fatty acid concentrations in the bloodstream, as well as a decrease in respiratory exchange ratio, indicating an increase in fat oxidation and sparing of carbohydrates as an energy source.
- The authors of the study concluded that “short-term ingestion of HCA increases fat oxidation during moderate intensity exercise also in untrained men” 15
Dosage For Fat Burninglinical trials have used very different doses — as low as 500 mg and as high as 4667 mg of HCA
Supplements in Review Saysstrong>Garcinia cambogia extract containing 500 mg HCA, 1-3 times daily.
Garcinia cambogia’s weight loss effects are unreliable and inconclusive. The research that exists seems to suggest that G cambogia’s weight loss effects are not nearly as strong and reliable in humans as they are in animals. But if you do decide to give it a try, it’s a good idea to combine it with exercise, since it has been shown to increase fat oxidation during physical activity.
500 mg of HCA seems to be the minimum dose needed. Although clinical trials have used a large range of doses, it seems that Garcinia cambogia extract containing roughly 500 mg HCA is a good starting point. If you find that it works well, you can consider moving up to 3 daily doses.
- Watson JA, et al. Tricarballylate and hydroxycitrate: substrate and inhibitor of ATP: citrate oxaloacetate lyase. Arch Biochem Biophys. 1969 Dec. 135(1):209-17. ↩
- Watson, John A & Lowenstein, John M. Citrate and the Conversion of Carbohydrate into Fat. The Journal of Biological Chemistry. Vol 245 No 22, 5993-6002. 1970. ↩
- Ohia SE, et al. Safety and mechanism of appetite suppression by a novel hydroxycitric acid extract (HCA-SX). Mol Cell Biochem. 2002 Sep;238(1-2):89-103. ↩
- Hayamizu K, et al. Effect of Garcinia cambogia extract on serum leptin and insulin in mice. Fitoterapia. 2003 Apr;74(3):267-73. ↩
- Mattes, RD & Bormann, L. Effects of (-)-hydroxycitric acid on appetitive variables. Physiol Behav. 2000 Oct 1-15;71(1-2):87-94. ↩
- Onakpoya I, et al. The Use of Garcinia Extract (Hydroxycitric Acid) as a Weight Loss Supplement: A Systematic Review and Meta-Analysis of Randomised Clinical Trials. J Obes. 2011:2011;509038. ↩
- Lim K, et al. (-)-Hydroxycitric acid ingestion increases fat utilization during exercise in untrained women. J Nutr Sci Vitaminol (Tokyo). 2003 Jun;49(3):163-7. ↩
- van Loon LJ et al. Effects of acute (-)-hydroxycitrate supplementation on substrate metabolism at rest and during exercise in humans. Am J Clin Nutr. 2000 Dec;72(6):1445-50. ↩
- Leonhardt M, et al. Effect of hydroxycitrate on respiratory quotient, energy expenditure, and glucose tolerance in male rats after a period of restrictive feeding. 2004 Oct;20(10):911-5. ↩
- Kim KY, et al. Garcinia cambogia Extract Ameliorates Visceral Adiposity in C57BL/6J Mice Fed on a High-Fat Diet. Biosci Biotechnol Biochem. 72(7), 1772-1780, 2008. ↩
- Heymsfield SB et al. Garcinia cambogia (hydroxycitric acid) as a potential antiobesity agent: a randomized controlled trial. JAMA. 1998 Nov 11;280(18):1596-600. ↩
- Kriketos AD et al. (-)-Hydroxycitric acid does not affect energy expenditure and substrate oxidation in adult males in a post-absorptive state. Int J Obes Relat Metab Disord. 1999 Aug;23(8):867-73. ↩
- Hayamizu K, et al. Effects of Garcinia cambogia (Hydroxycitric Acid) on Visceral Fat Accumulation: A Double-Blind, Randomized, Placebo-Controlled Trial. Current Therapeutic Research. Volume 64, No. 8. Sep-Oct 2003. ↩
- Preuss HG, et al. Effects of a natural extract of (-)-hydroxycitric acid (HCA-SX) and a combination of HCA-SX plus niacin-bound chromium and Gymnema sylvestre extract on weight loss. Diabetes Obes Metab. 2004 May;6(3):171-80. ↩
- Tomita K, et al. (-)-hydroxycitrate ingestion increases fat oxidation during moderate intensity exercise in untrained men. Biosci Biotechnol Biochem. 2003 Sep;67(6):1999-2001. ↩