talian scientists are testing a new diet pill that turns into a clear, gelatinous blob the size of a tennis ball that may help shrink waistlines by giving dieters a sense of satiety.

The pill, currently undergoing clinical trials at Rome's Policlinico Gemelli hospital, would be downed with two glasses of water at the first sign of a stomach rumble.

"The effect is like eating a nice plate of pasta," said Luigi Ambrosio, lead researcher on the project at the National Research Council's Institute for Composite and Biomedical Materials in Naples. "If you sit down for a meal with a stomach that already feels full, you'll end up eating less."

The unnamed pill is made from a cellulose compound of hydrogel, a material that's powdery when dry but plumps up to a cousin of Jell-O when wet. The gel can soak up to 1,000 times its weight. A gram in capsule form quickly balloons from the size of a spit wad to a ball that holds nearly a liter of liquid.

Growing waistlines are an increasingly hefty issue. The World Health Organization calls "obesity one of today's most blatantly visible - yet most neglected - public health problems." The WHO estimates that 1 billion adults worldwide are overweight, 300 million of them obese. Attendant illnesses include type-2 diabetes, cardiovascular disease, hypertension, stroke and certain forms of cancer.

Ambrosio and fellow researcher Luigi Nicolais, now minister for reform and innovation, noticed the burgeoning girth of Americans during a trip to the United States in the '90s.

The pair had been working with a team to develop super-absorbent materials for Swedish paper-product company Sca and wondered whether a hydrogel could produce an effect similar to gastric banding -- without the surgery.

Along the way, they discovered the spongelike material could be used to treat edemas, and are currently experimenting with it as a way to slow-water plants. The versions of the material for use in the diet pill is biocompatible, so the body just flushes it out, the scientist say.

Jelly belly: from about the size of a spit wad the compound grows to a tennis ball so dieters sit down feeling full.

Lona Sandon, a dietitian at UT Southwestern Medical Center in Dallas, sighed slightly before commenting.

"I don't think we'll find the answer to obesity in a pill," said Sandon, who is also a spokeswoman for the American Dietetic Association. "The only long-term solution is cutting back calories and getting exercise."

Though it may not be a magic bullet, some experts think it could help those whose girth has already grown out of control.

"A pill like that one could be a valid aid when you've already got a serious problem," said professor Antonino De Lorenzo of Rome's Tor Vergata University, who has conducted extensive research on benefits of the classic Mediterranean diet. "The real challenge is teaching people to eat properly before they need it."

If trials are successful, researchers hope to put the gel pill within easy reach of calorie counters on both the EU and North American markets in about a year.

"Obesity is such an enormous problem," said Ambrosio. "If we managed to reduce it by even 10 percent with this pill, it would be a huge accomplishment."