(CBS) Each year, people spend more than $40 billion on products designed to help them slim down. None of them seem to be working very well.

Now along comes hoodia. Never heard of it? Soon itll be tripping off your tongue, because hoodia is a natural substance that literally takes your appetite away.

Its very different from diet stimulants like Ephedra and Phenfen that are now banned because of dangerous side effects. Hoodia doesnt stimulate at all. Scientists say it fools the brain by making you think youre full, even if youve eaten just a morsel. Correspondent Lesley Stahl reports.

Hoodia, a plant that tricks the brain by making the stomach feel full, has been in the diet of South Africas Bushmen for thousands of years.

Because the only place in the world where hoodia grows wild is in the Kalahari Desert of South Africa.

Nigel Crawhall, a linguist and interpreter, hired an experienced tracker named Toppies Kruiper, a local aboriginal Bushman, to help find it. The Bushmen were featured in the movie The Gods Must Be Crazy.

Kruiper led 60 Minutes crews out into the desert. Stahl asked him if he ate hoodia. I really like to eat them when the new rains have come, says Kruiper, speaking through the interpreter. Then theyre really quite delicious.

When we located the plant, Kruiper cut off a stalk that looked like a small spiky pickle, and removed the sharp spines. In the interest of science, Stahl ate it. She described the taste as a little cucumbery in texture, but not bad.

So how did it work? Stahl says she had no after effects - no funny taste in her mouth, no queasy stomach, and no racing heart. She also wasnt hungry all day, even when she would normally have a pang around mealtime. And, she also had no desire to eat or drink the entire day. Id have to say it did work, says Stahl.

Although the West is just discovering hoodia, the Bushmen of the Kalahari have been eating it for a very long time. After all, they have been living off the land in southern Africa for more than 100,000 years.

Some of the Bushmen, like Anna Swartz, still live in old traditional huts, and cook so-called Bush food gathered from the desert the old-fashioned way.

The first scientific investigation of the plant was conducted at South Africas national laboratory. Because Bushmen were known to eat hoodia, it was included in a study of indigenous foods.

What they found was when they fed it to animals, the animals ate it and lost weight, says Dr. Richard Dixey, who heads an English pharmaceutical company called Phytopharm that is trying to develop weight-loss products based on hoodia.

Was hoodias potential application as an appetite suppressant immediately obvious?

No, it took them a long time. In fact, the original research was done in the mid 1960s, says Dixey.

It took the South African national laboratory 30 years to isolate and identify the specific appetite-suppressing ingredient in hoodia. When they found it, they applied for a patent and licensed it to Phytopharm.

Phytopharm has spent more than $20 million so far on research, including clinical trials with obese volunteers that have yielded promising results. Subjects given hoodia ended up eating about 1,000 calories a day less than those in the control group. To put that in perspective, the average American man consumes about 2,600 calories a day; a woman about 1,900.

If you take this compound every day, your wish to eat goes down. And weve seen that very, very dramatically, says Dixey.

But why do you need a patent for a plant? The patent is on the application of the plant as a weight-loss material. And, of course, the active compounds within the plant. Its not on the plant itself, says Dixey.

So no one else can use hoodia for weight loss? As a weight-management product without infringing the patent, thats correct, says Dixey.

But what does that say about all these weight-loss products that claim to have hoodia in it? Trimspa says its X32 pills contain 75 mg of hoodia. The company is pushing its product with an ad campaign featuring Anna Nicole Smith, even though the FDA has notified Trimspa that it hasnt demonstrated that the product is safe.

Some companies have even used the results of Phytopharms clinical tests to market their products.

This is just straightforward theft. Thats what it is. People are stealing data, which they havent done, theyve got no proper understanding of, and sticking on the bottle, says Dixey. When we have assayed these materials, they contain between 0.1 and 0.01 percent of the active ingredient claimed. But they use the term hoodia on the bottle, of course, so they -- does nothing at all.

But Dixey isnt the only one whos felt ripped off. The Bushmen first heard the news about the patent when Phytopharm put out a press release. Roger Chennells, a lawyer in South Africa who represents the Bushmen, who are also called the San, was appalled.

The San did not even know about it, says Chennells. They had given the information that led directly toward the patent.

The taking of traditional knowledge without compensation is called bio-piracy.

You have said, and Im going to quote you, that the San felt as if someone had stolen the family silver, says Stahl to Chennells. So what did you do?

I wouldnt want to go into some of the details as to what kind of letters were written or what kind of threats were made, says Chennells. We engaged them. They had done something wrong, and we wanted them to acknowledge it.

Chennells was determined to help the Bushmen who, he says, have been exploited for centuries. First they were pushed aside by black tribes. Then, when white colonists arrived, they were nearly annihilated.

About the turn of the century, there were still hunting parties in Namibia and in South Africa that allowed farmers to go and kill Bushmen, says Chennells. Its well documented.

The Bushmen are still stigmatized in South Africa, and plagued with high unemployment, little education, and lots of alcoholism. And now, it seemed they were about to be cut out of a potential windfall from hoodia. So Chennells threatened to sue the national lab on their behalf.

We knew that if it was successful, many, many millions of dollars would be coming towards the San, says Chennells. Many, many millions. Theyve talked about the market being hundreds and hundreds of millions in America.

In the end, a settlement was reached. The Bushmen will get a percentage of the profits -- if there are profits. But thats a big if.

The future of hoodia is not yet a sure thing. The project hit a major snag last year. Pharmaceutical giant Pfizer, which had teamed up with Phytopharm, and funded much of the research, dropped out when making a pill out of the active ingredient seemed beyond reach.

Dixey says it can be made synthetically: Weve made milligrams of it. But its very expensive. Its not possible to make it synthetically in whats called a scaleable process. So we couldnt make a metric ton of it or something that is the sort of quantity youd need to actually start doing something about obesity in thousands of people.

Phytopharm decided to market hoodia in its natural form, in diet shakes and bars. That meant it needed the hoodia plant itself.

But given the obesity epidemic in the United States, it became obvious that what was needed was a lot of hoodia - much more than was growing in the wild in the Kalahari. And so they came here.

60 Minutes visited one of Phytopharms hoodia plantations in South Africa. Theyll need a lot of these plantations to meet the expected demand.

Agronomist Simon MacWilliam has a tall order: grow a billion portions a year of hoodia, within just a couple of years. He admitted that starting up the plantation has been quite a challenge.

The problem is were dealing with a novel crop. Its a plant weve taken out of the wild and were starting to grow it, says MacWilliam. So we have no experience. So its different? diseases and pests which we have to deal with.

How confident are they that they will be able to grow enough? Were very confident of that, he says. Weve got an expansion program which is going to be 100s of acres. And well be able - ready to meet the demand.

This could be huge, given the obesity epidemic. Phytopharm says its about to announce marketing plans that will have meal-replacement hoodia products on supermarket shelves by 2008.

MacWilliam says these products are a slightly different species from the hoodia Stahl tasted in the Kalahari Desert. Its actually a lot more bitter than the plant that you tasted, says MacWilliam.

The advantage is this species of hoodia will grow a lot faster. But more bitter? How bad could it be? Stahl decided to find out. Not good, she says.

Phytopharm says that when its product gets to market, it will be certified safe and effective. They also promise that itll taste good.