Cactus that promises to curb the appetite

A multi-million pound race between the world's biggest food companies is under way to tackle the global obesity epidemic by producing the first clinically-tested "satiety pill".

Three conglomerates - the Anglo-Dutch firm Unilever, France's Danone and Kraft in America - are researching compounds to achieve the hallowed goal of inducing people to eat less by suppressing their appetite.

With 300 million people worldwide rated as overweight or obese, the annual global cost of treatment and economic loss from the epidemic is now £100bn.

Scientists are increasingly placing their hopes in a range of natural substances which have the effect of duping the brain into "satiety" - the feeling of a full stomach. In the last 12 months, patents have been given appetite-suppressing extracts including Korean pine nuts and chicory roots. But at the head of the race to cash in on the £3bn worldwide market for dietary control products is Hoodia gordonii - a spiny cactus, which takes five years to mature in the Kalahari desert.

Hoodia contains a secret weapon - a compound known as P57 which has been isolated by a British bio-technology company, Phytopharm, and is now at the heart of a £21m research scheme funded by Unilever.

Phytopharm announced last month that it was making good progress in clinical trials of P57. The cucumber-like core of the Hoodia has been used for centuries by indigenous San tribesmen to stave off hunger pangs. They eat it on long hunting trips.

Unilever has struck a deal with the San to pay the tribe a royalty from the sales of any product containing P57 to be used in a social programme.

Phytopharm, which will also receive a royalty on sales of all products containing its Hoodia extract, warned last month that it was talking with authorities to curtail the sale of "Hoodia" products on the internet which claim to cause weight loss. Unilever is working to launch a range of "hunger buster" products based on Hoodia in 2009.

Phytopharm found that the compound closely mimics a natural substance in the body which sends a satiety message to the hypothalamus - the part of the brain that controls appetite.

Trials have shown that those taking P57 can cut their consumption by as much as 1,000 calories per day. The recommended calorie total for an adult man is 2,500 per day and for a woman, 2,000. A Unilever spokesman said: "We don't want to put our name to something that is not backed 100 per cent by the science behind it. We are now satisfied that the product works and has the potential to help with weight management."

The cash and energy being pumped into Unilever's project is mirrored by its rivals. Danone has patented new types of dietary fibre which slow the passage of food through the digestive system, making people feel full for longer. Kraft is working on a special form of starch which resists being broken down by the body, again designed to create the sense that the stomach is full.

But a senior executive with one conglomerate told The Independent: "Satiety has the potential to be one of the biggest earners of the next five years."

Many of the substances, including P57, work by affecting a mechanism in the ileum, part of the lower intestine, where the presence of fat triggers a response of satiety to the brain.

This "ileal brake" is triggered or mimicked by the compounds by disguising the fat molecules until they reach the ileum. In one case, the body is convinced it has consumed 500 calories when in reality it has had just 190.

However, according to Gary Frost, professor of nutrition and dietetics at Surrey University, humans have a "squirreling" instinct which encourages them to eat to excess in preparation for times of food scarcity. "There is a sense that for the company or companies that can isolate a proven appetite suppressant, there is a market waiting that would entail the vast majority of the population," he said. "It is a glittering prize but a controversial one - can you confidently say that one food will halt your desire for another?"

Neville Rigby, spokesman for the International Obesity Task Force, said: "The key to tackling obesity is eating decent food and balancing your calorie intake with the amount of energy you burn. There is no magic bullet."