Hydroxy-citric acid

Hydroxy-citric acid (HCA) is a substance unique to the fruit of the Garcinia tree (Brindleberry) that inhibits the synthesis of fats.

When carbohydrates are eaten they are broken down into glucose and used for energy. The glucose that is not used immediately as energy is stored in the muscles and liver as glycogen. Once the glycogen stores become full, an enzyme known as ATP-citrate lyase acts with any excess glucose molecules to produce fat and cholesterol. HCA temporarily inhibits this final process by suppressing the action of this enzyme.

According to McCarty, because excess glucose is no longer being turned into fatty tissue, it remains stored as glycogen and the brain receives a message that energy reserves are full and so no more food needs to be taken in.