Few obesity surgeons are as famous, or as busy, as Mathias "Mal" Fobi of Los Angeles. Fobi, who has privileges at four hospitals including Cedars-Sinai Medical Center, says he has performed 8,000 weight loss surgeries since 1977. The 53-year-old surgeon, whose patients come from as far as South Africa and Saudi Arabia, advertises extensively on radio and television in Southern California promoting the Fobi pouch, a form of the gastric bypass operation he invented.

He has appeared in tabloid articles that chronicle the weight travails of his celebrity patients: comedian Roseanne Barr and her teenage daughter, who had surgery several years ago, and JoMarie Payton, star of the television show "Family Matters." Last month Fobi was prominently featured on the CBS television newsmagazine "48 Hours." Two days after the broadcast Fobi said his office received more than 1,500 inquiries, which have trickled off to about 150 per day.

Fobi, who employs a publicist, is well-known for his outspoken views on obesity, which he espouses during his appearances on television talk shows and on his Web site. Surgery is not a treatment for severe obesity, he says, it's the only treatment. "Those people who are advocating diets and exercise for severe obesity are quacks," he asserted in a recent interview.

But what most prospective patients probably don't know is that in the past 23 years, the board-certified surgeon said he has been named as a defendant in more than 39 lawsuits, the vast majority of which are malpractice cases. Court records show that 10 of these cases involved the deaths of patients. Four suits were filed by patients who developed severe wound infections after surgery, which they claim were not treated properly. In two cases patients claimed that their incisions, which run from breastbone to navel, literally opened up. Fobi said he paid $100,000 to settle one of these cases and he won another at trial. He said he has made payments ranging from $29,000 to $100,000 to settle four cases; in all of the settlements Fobi denied any liability. Many of the other malpractice suits against him, he said, have been dismissed.

Nor is there any way for prospective patients to know that the California Medical Board is, according to knowledgeable sources, investigating Fobi. "Investigations are not public record," said board spokeswoman Candis Cohen, who added that the surgeon has never been disciplined by the board.

Fobi said in interviews that his operation, which he teaches other surgeons to perform, is the "safest and most effective procedure anywhere." He said he believes the large number of malpractice cases is evidence that he is the victim of a conspiracy perpetrated by "people who are trying to defame and marginalize me," chiefly a rival surgeon and a few lawyers who are soliciting malpractice cases.

Fobi said he believes his foes are motivated largely by racism and that he is "a great surgeon doing great things."

"If I was a white surgeon with my credentials and my capabilities, I would be recruited" by academic medical centers, he said.

Currently, court records show, six malpractice cases are pending against Fobi, five in Los Angeles and one in Las Vegas. In the past year Fobi has won two malpractice cases, both involving the deaths of patients. His most recent victory occurred earlier this month after a five-week trial. A Los Angeles Superior Court jury cleared him of malpractice in connection with the 1997 death of a woman who succumbed to a massive infection several years after Fobi operated on her. Her family's attorney argued that the infection that killed her was caused by a gangrenous bowel, a complication of Fobi's surgery. Fobi's attorney argued that her death did not result from his treatment, but was due to an E. coli infection.

The Fobi pouch, which essentially combines two of the most common obesity operations, involves surgically separating most of the stomach from the esophagus and then forming a new pouch, which is attached to the small intestine. Fobi places an elastic band around the pouch to slow the passage of food.

So far the only case Fobi has lost in court was brought by Lisa Ann Ross, 33, of Long Beach, Calif. Last year a jury in Los Angeles Superior Court found Fobi guilty of malpractice and negligent misrepresentation in his treatment of Ross. The jury awarded Ross $2.4 million, an award cut by a judge to $1.06 million; Fobi said the case ultimately was settled for $875,000.

In 1996 Ross, 5 feet 5 inches tall and then weighing 230 pounds, underwent a Fobi pouch procedure at Cedars-Sinai. During the two-week trial she testified that Fobi told her the surgery was reversible and that it had been explicitly endorsed by the National Institutes of Health. The jury decided that both statements were false. During the trial Fobi denied that he mislead or mistreated Ross.

Shortly after surgery, Ross said in an interview, she began vomiting. "I threw up all day long," she recalled. "I never stopped being sick." Within six months her weight had plummeted to 97 pounds. She testified that she consulted Fobi repeatedly and he told her she wasn't eating properly but that nothing serious was wrong. Fobi said in an interview that Ross's problems were "resolving" when she sought treatment at UCLA.

Doctors at UCLA Medical Center, where she sought a second opinion, disagreed. They told Ross she had life-threatening malnutrition and a bowel obstruction caused by the erosion of the band Fobi had placed around her new stomach. In Ross's case the band had eroded and was preventing any food from entering her stomach. Ross subsequently underwent extensive reconstructive surgery at UCLA; she said she now weighs about 118 pounds but suffers from chronic abdominal pain and a host of other disabling ailments.

Fobi denied any wrongdoing in his treatment of Ross. "It was a case that my [malpractice insurer] and my attorney thought was a nonsense case," Fobi said in an interview.

Another case against Fobi, now pending in Las Vegas, was filed by the estate of Bonnie Robertson. Fobi operated on Robertson in July 1993. She died 18 months later weighing 85 pounds. The lawsuit alleges that Robertson died of chronic malnutrition due to unremitting vomiting caused by complications of her surgery. Fobi said he did nothing wrong and that Robertson died because she failed to comply with his recommendations, which included additional surgery.

In 1987, court records show, Fobi paid $33,000 to settle a case brought by a nursing supervisor in which he stipulated to causing "willful personal injury." Court records show that Fobi slapped the nurse in the face during an argument while he was scrubbing for emergency surgery.

"That was not a malpractice case," Fobi said, and declined to discuss it.

Some surgeons say they are alarmed by Fobi's surgical techniques and his eponymous procedure, which they say consists of dangerous and untested modifications of the standard gastric bypass operation.

Edward H. Livingston, vice chairman of surgery at UCLA Medical Center, says the band Fobi places around the pouch can erode, causing intestinal obstructions, infection, intractable vomiting and sometimes death.

"Quite frankly, most of the people who develop modifications don't really understand science or surgery, like Dr. Fobi," said Livingston, who adds that he has operated on five of Fobi's former patients to correct complications, some of them life-threatening. Livingston also has testified against Fobi as a paid expert in several malpractice cases, including the one brought by Lisa Ross.

"It's an artifact of the fact that surgery is unregulated and there's no oversight by the government or anyone else," he added. "That's why Fobi can invent his pouch and say it's better without any evidence. I think people have a right to know whether a doctor is performing an experimental procedure when they walk into his office."

Fobi dismisses such criticism and says Livingston is "no expert." The UCLA surgeon, he said, "is doing the procedure I did in 1977 . . . which will result in weight gain." Fobi said that 3 percent of his patients need revisions and that his mortality rate is less than 0.5 percent.

Livingston said that "most surgeons do the operation I do, which has been subjected to randomized clinical trials and has been systematically studied. I didn't make it up."

Unlike some of his more orthodox colleagues who perform surgery only on adults, Fobi says he sometimes operates on obese children; his youngest patient was a 9-year-old girl who weighed 347 pounds. He also operates on people who are not severely obese and have a body mass index of 30, not the 40 recommended by NIH. "We treat the patients, not the numbers," Fobi said.

One of Fobi's most satisfied patients--and one of the biggest on whom he has ever operated--is Willie Collins, 42, of Corpus Christi, Tex. Collins had surgery in May 1998: at the time he weighed 768 pounds and had to be weighed on a truck scale. When he flew to Los Angeles, Collins had to buy two airline seats.

Collins said he now weighs about 400 pounds. He is still losing weight and has had no complications other than an incisional hernia, which is not uncommon among super-obese patients. "I can go dancing with my wife, I can walk without panting, I can buy clothes in a store and I no longer obsess about food the way I used to. I feel great and I have Dr. Fobi to thank."

Researcher Julia Scheeres contributed to this story.