There is a substance in hoodia gordonii that appears to trigger the hypothalamus, which may reduce your appetite. There really haven't been many studies performed with hoodia use in humans, but the San Bushmen of the Kalahari have used hoodia to ward off hunger pangs for many years.
Hoodia appears to be safe for human use and can be found in a few over-the-counter weight-loss products, but you need to be cautious about taking weight-loss aids. According to the United States Food and Drug Administration, some weight loss aids actually contain hidden drugs and may not be safe.
You should also speak with your health care provider before taking hoodia or any other weight loss aid, and before going on any type of weight loss diet.
Losing weight is still about eating fewer calories every day. Taking the edge off hunger may help, but you still need to make smart food choices and control your calorie intake - there's no way around that. Eat foods that are nutrient-dense with fewer calories such as fruits, vegetables, lean meats, poultry, fish, non-fat dairy products and whole grains.
MacLean DB, Luo LG. "Increased ATP content/production in the hypothalamus may be a signal for energy-sensing of satiety: studies of the anorectic mechanism of a plant steroidal glycoside." Brain Research Volume 1020, Issues 1-2 , 10 September 2004, Pages 1-11.
Seamon E, Ulbricht C, Weissner W, Woods J. "Hoodia (Hoodia gordonii) - Professional Monograph." Natural Standard Collaborative. Accessed February 9, 2012. http://naturalstandard.com.
United States Food and Drug Administration. "Medication Health Fraud - Tainted Weight Loss Products. Accessed February 9, 2012. http://www.fda.gov/Drugs/ResourcesForYou/Consumers/BuyingUsingMedicineSafely/MedicationHealthFraud/ucm234592.htm.