There's a great article about Hoodie and the studies supporting it from someone skeptical at http://skepchick.org/blog/?p=46
"I turned to my friend Google. I was shocked to find that as claimed on the site, Hoodia really WAS mentioned on the BBC.
Deep inside the African Kalahari desert, grows an ugly cactus called the Hoodia. It thrives in extremely high temperatures, and takes years to mature. And not only that, but it actually sounds like it may even work:
The San Bushmen of the Kalahari, one of the world’s oldest and most primitive tribes, had been eating the Hoodia for thousands of years, to stave off hunger during long hunting trips.
Half were given Hoodia, half placebo. Fifteen days later, the Hoodia group had reduced their calorie intake by 1000 a day. The journalist even traveled to the Kalahari to try it for himself:
It was a stunning success.
The plant is said to have a feel-good almost aphrodisiac quality, and I have to say, we felt good.
But more significantly, we did not even think about food. Our brains really were telling us we were full. It was a magnificent deception."