Fort Lauderdale, Fla. ? A kind of pacemaker for the tummy, an implanted electrical device that fools the body into feeling full, appears to be an effective alternative to radical digestive surgery for helping obese people shed large amounts of weight.

If it proves out in larger studies, the experimental device could offer a new way to help very large people slim down when they cannot lose weight on diets or with appetite-suppressing drugs. Researchers Sunday presented preliminary data on the usefulness of the approach, which already has been tested on 450 people to show its safety.

Surgical techniques that shrink the stomach and reroute the digestive tract are the only highly reliable way to make obese people lose weight. However, this is major surgery that carries significant risk, including a 1 percent chance of death, and researchers are searching for ways to do the job more safely.

The new device is called an implantable gastric stimulator and is similar to a cardiac pacemaker. But instead of stimulating the heart, this one is attached to the wall of the stomach and is intended to reduce feelings of hunger.

The researchers implanted the devices in 30 obese women and men whose average weight was 242 pounds. Their average body mass index, or BMI, was 42. The healthy cutoff for the height-to-weight ratio is 25; 30 is considered obese.

After a year with the implant, two-thirds of the volunteers had lost weight. The average was an 18 percent drop in their excess weight.

“The results are promising, although we still have a long way to go,” Dr. Scott Shikora said. “I believe in my heart this is a very exciting breakthrough in our field.”

Shikora, head of bariatric surgery at Tufts-New England Medical Center in Boston, presented the study in Fort Lauderdale at the annual scientific meeting of the American Association for the Study of Obesity. It was financed by the device’s developer, Transneuronix Inc. of Mount Arlington, N.J.

The system uses an electrical pulse generator, a little larger than a silver dollar, that is placed under the skin in the abdomen and connected to the stomach with two wires. Implanting it takes less than an hour and is done as an outpatient laproscopic procedure.

“These early findings are exciting,” said Dr. Samuel Klein of Washington University, the obesity association’s president. “This is a potential new approach for the management of obesity that is separate from drugs or surgery.”

The device already is on the market in Europe but still is several years away from Food and Drug Administration approval in the United States. Steven Adler, Transneuronix’s executive vice president, said the company hoped in a few months to begin a study on 120 patients that would take two years to complete.

Weight reduction varied widely. While about one-third in the study lost nothing, some had stunning success. One patient lost 104 percent of her excess weight.