In studies, 1–3 g/day of HCA.
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Garcinia cambogia is a tropical fruit native to Southeast Asia and equatorial Africa, whose rind contains hydroxycitric acid (HCA), a compound similar to citric acid that the weight-loss supplement industry has heavily promoted over the past two decades, especially after its appearance on popular television shows; the reality of the clinical evidence is very far from the marketing, and it deserves a calm look before making consumer decisions.
The theoretical mechanism is reasonable at the molecular level: HCA inhibits ATP-citrate lyase, a key enzyme in the de novo synthesis of fatty acids from carbohydrates, which in cell cultures and animal models reduces hepatic lipogenesis and increases fat oxidation; translating this biochemical effect into clinically significant weight loss in humans has been the unfinished business, with consistently disappointing results.
Several meta-analyses have evaluated Garcinia cambogia for weight loss: the reductions in weight are small (in the range of 1-2 kilos in 8-12 week trials), of highly debatable clinical relevance, and disappear when studies are weighted by methodological quality; the most rigorous trial, published in JAMA in 1998 with 135 people, found no significant differences from placebo in weight loss or body fat loss at 12 months.
The reasonable conclusion is that Garcinia cambogia is one of the many products whose main effect on weight is that of placebo and of the dietary change that anyone adopts when committing to a weight-loss intervention; anyone seeking to lose weight sustainably will get better results with a moderate calorie deficit, regular exercise, and sufficient dietary protein than with any HCA supplement, whatever the dose or brand.
The most serious concern about Garcinia cambogia is not its lack of efficacy but its liver safety profile: since 2009, dozens of cases of acute hepatitis associated with its use have been reported, some severe and requiring liver transplantation, which led the FDA and several European agencies to issue formal warnings and, in some cases, to withdraw specific products from the market.
The hepatotoxicity appears to be idiosyncratic (not predictable by dose) and rare in absolute terms, but the risk-benefit balance is clearly unfavorable when you consider that the benefit for weight loss is marginal or nil and the risk, although rare, is potentially catastrophic; products combined with other "fat burners" (especially concentrated green tea extract) carry an even higher risk because of additive toxicity.
For blood glucose and insulin resistance, some small studies have shown modest improvements, but the evidence is heterogeneous and clearly inferior to other nutritional interventions with a better safety profile; for lipid profile, the effect is marginal and not clinically relevant in most people.
The doses studied range from 1,500 to 3,000 milligrams daily of extract standardized to 50-60 percent HCA, but the clinical reality is that the magnitude of the benefit does not justify the liver risk or the cost compared with far more effective and safer dietary and exercise interventions; my honest recommendation as a science communicator is that Garcinia cambogia should not be part of a reasonable weight-loss strategy in light of the available evidence.
People with preexisting liver disease, those taking hepatotoxic drugs (regular acetaminophen, some antibiotics, high-dose statins, antiepileptics), those taking antidiabetic drugs (risk of hypoglycemia) or serotonergic antidepressants (theoretical risk of serotonergic potentiation, with cases of serotonin syndrome described) are specifically at risk and should avoid Garcinia; it is also advisable to avoid it in pregnancy, breastfeeding, children, and decompensated psychiatric disorders.
Information, not medical advice. Scientific evidence reflects the quality of the studies.