Hoodia

A succulent plant native to South Africa’s Kalahari Desert, hoodia is the chief ingredient in TrimSpa, Hoodoba, and many other weight-loss supplements. The indigenous San tribe (formerly called Bushmen) have long chewed the plant’s stalks to curb appetite, quench thirst, and increase endurance when on long hunting treks and during food shortages. There are many species; the one thought to suppress appetite is Hoodia gordonii.

Claims, purported benefits: Suppresses appetite, promotes weight loss.

Evidence: Years ago South Africa’s national laboratory found that hoodia produced weight loss in animals. More recently, the plant’s active ingredient was identified as P57 and patented. The substance is thought to stimulate a part of the brain that shuts down hunger signals, so it may fool you into thinking you’re full even if you haven’t eaten. In a pharmaceutical company study, men who took P57 cut back on calories and lost body fat. But this is the only study on people—and it was very small and short and hasn’t been published.

Bottom line: Whether or not hoodia has weight-loss effects, products are likely to contain little or none of the alleged active ingredient, or be watered down with other unproven weight-loss ingredients. None currently contain the patented P57. Even if a product claims to be 100% hoodia, you can’t be sure that is true or that you’re even getting the right plant or plant part. Hoodia is now grown from China to Texas, but no one knows if plants outside the Kalahari region have the same effect in the body. And no one knows if hoodia is safe. The San themselves use hoodia sparingly, and certainly not for weight loss. Some researchers caution that "unwanted effects on the liver" have been observed.