HCA (hydroxycitric acid) is a close relative of citric acid, the agent that gives citrus fruits their characteristic tart flavor. HCA is obtained as a 50% standardized extract of Garcinia cambogia, a small fruit from southern India, where it has been used for centuries as a food preservative, flavoring agent, and digestive aid.

HCA exerts its weight control effect through its inhibition of the enzyme ATP citrate lyase, playing a critical role in energy storage.*1 When calorie intake exceeds the body’s energy needs, the excess glucose is converted into glycogen, which is stored in the liver and muscles for future conversion into energy. Weight gain occurs after the body's capacity for glycogen storage is reached. At this point, glucose from excessive calorie intake is converted into acetyl coenzyme A via a metabolic pathway involving ATP-citrate lyase and then into fat molecules, which are stored in fat cells. HCA has been shown to bind to ATP-citrate lyase to reduce the production of acetyl coenzyme A and also increase the ability of the liver and muscles to synthesize and store glycogen.*2

Research has shown that HCA is absorbed with blood levels of HCA peaking two hours after ingestion and remaining in the blood for between four and nine hours after ingestion.3,4

1- Szutowicz A, Stepien M, Lysiak W, Angielski S. Effect of (-)hydroxycitrate on the activities of ATP citrate lyase and the enzymes of acetyl-CoA metabolism in rat brain. Acta Biochim Pol. 1976, 23(2-3):227-34.
2- Lim K, Ryu S, Nho HS, Choi SK, Kwon T, Suh H, So J, Tomita K, Okuhara Y, Shigematsu N. (-)-Hydroxycitric acid ingestion increases fat utilization during exercise in untrained women. J Nutr Sci Vitaminol (Tokyo). 2003 Jun, 49(3):163-7.
3- Loe YC et al. "Gas chromatography/mass spectrometry method to quantify blood hydroxycitrate concentration." Anal Biochem 292(1):148-54, 2001.
4- Loe YC et al. "Time course of hydroxycitrate clearance in fasting and fed humans." FASEB J 15(4):632, Abs. 501.1, 2001.
5- Preuss HG, Bagchi D, Bagchi M, Rao CV, Dey DK, Satyanarayana S. 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.