Wilde said the technique should work with any foods that contain fat, like dairy products, precooked sauces, mayonnaise, breads and pastries, and that taste would probably not be affected.

If all goes well, products could be on shelves within a few years, he said.

In another technique, scientists at the University of Newcastle have been testing a seaweed extract called alginate that reduces fat absorption by cutting the level of glucose digested by the body before it gets broken down in the large intestine.

That is somewhat similar to how some diet drugs work, such as orlistat, marketed as Xenical by Roche Holding AG, and Alli by GlaxoSmithKline PLC.

Orlistat blocks fat absorption, but can result in side effects like gas and diarrhea. Scientists think that those side effects could be avoided if fiber intake is increased.

In taste tests by several dozen people, participants found that alginate-enhanced bread tasted as good as or even better than regular bread, said molecular physiology professor Jeffrey Pearson, who is leading the Newcastle research.

"It would be very helpful to reduce people's calorific levels by stealth, so they don't notice there's been a change," Pearson said. "People don't want to completely change their lifestyle and stop eating. ... This lets them indulge again."

Food companies and pharmaceutical firms are also exploring ways to tinker with appetite. In 2004, Unilever bought the rights to a South African plant traditionally chewed by tribesman to ward off hunger.

A small study found that people given the plant extract, hoodia gordonii, for 15 days had slashed their food intake by 1,000 calories compared to people on a placebo. A Unilever spokesman said the extract would be added to a food or beverage and could hit the market within a few years.

Not all experts are convinced appetite-stopping foods will be a cure-all for obesity.

"Humans are a very messy group to control," said Alice H. Lichtenstein, a nutritionist at Tufts University. People are motivated to eat for various reasons, from taste to price to childhood nostalgia, she said.

Other experts worry about how such foods might be regulated once they are available. "If you have this magic bullet, how do you control who gets it? What do you do about anorexics or female adolescents?" asked Peter Fryer, a chemical engineer at the University of Birmingham who also researches modified foods.

But experts agree that foods that cut appetite could be an effective tool against obesity.

"Dieting is an awful bore and most human beings are very gullible," Bloom said. "We need all the help science can provide."

(Agencies via China Daily October 24, 2008)