Hydroxy Citric Acid (HCA)

What is it? HCA is a small molecule found in low concentrations in some plants, especially fruits. Its proponents claim that HCA can increase fat oxidation by inhibiting citrate lyase, an enzyme in cells that plays a crucial role in energy metabolism during a process known as 'lipogenesis'.

How does it work? There are two main claims; firstly that it helps stimulate fat oxidation and secondly that it helps keep excess body fat off, once it has been lost.

How strong is the evidence that it works? Weak. Initial evidence with rodents looked very promising, but the evidence for benefits of HCA in humans is rather less impressive. Most human studies have shown either no evidence or statistically insignificant evidence that HCA produces any effect, either by boosting fat oxidation or by stimulating body fat loss. HCA has consistently been one of the top-selling sports supplements, but it's hard to see why when there's little concrete scientific evidence to validate its use.