Gomez had considered a gastric bypass operation, a more complex kind of stomach stapling, but worried about risks from that surgery. It reduces the stomach to the size of a golf ball and reroutes the digestive tract.

Whether done through one large abdominal incision or several tiny ones, gastric bypass is far more invasive and increases chances for malnutrition because it repositions how the stomach attaches to the intestines to restrict calorie absorption.

Another popular weight-loss surgery option involves putting an adjustable band around the top part of the stomach to create a small pouch.

The experimental method Gomez had is the oral version of a different kind of stomach surgery, which reduces the size of the stomach with staples but doesn't reroute the digestive system.

Surgery is generally considered a last-resort treatment for obesity, which affects more than 15 million Americans. Still, demand is high. More than 200,000 Americans are expected to have conventional forms of obesity surgery this year, according to the American Society for Metabolic & Bariatric Surgery.

Dr. Scott Shikora, the society's president, called the oral procedure exciting and innovative, but said, "It is too early for us to say this is going to be a breakthrough."

Shikora said many U.S. obesity surgeons prefer the rerouting surgery or flexible bands, and that it remains to be seen whether the oral method has the same drawbacks as more outmoded stapling procedures.

The U.S. study is taking place at 10 centers. Patients will be followed for at least one year, with final results expected in 2010. They are randomly selected to undergo either the operation or a sham procedure.

Nishi said of 25 patients enrolled at his hospital, 17 got the real treatment, with no complications.

"I'm very impressed with it," Nishi said. So far, it looks like "a viable alternative," he said.

Satiety Inc., a California company that created the medical devices used in the technique, is paying for the research. Nishi said he has no financial ties to the company.

At Washington University School of Medicine in St. Louis, where the first U.S. procedure was done last summer, about 30 patients have undergone the treatment. Side effects have been minimal, including sore throats, nausea and some abdominal pain lasting less than a week, said Dr. J. Christopher Eagon. He said weight loss results from his center aren't yet available.