Jan. 5 (Bloomberg) -- Parts of Steve Jobs’s stomach, pancreas, bile duct and small intestine may have been removed to stop the spread of cancer. If so, the surgery may be fueling the Apple Inc. chief executive officer’s weight loss.

The so-called Whipple procedure, often used to treat pancreatic cancer, can lead to a digestive condition known as dumping syndrome that causes people to lose weight, said Simon Lo, director of the pancreas diseases program at Cedars-Sinai Medical Center in Los Angeles.

Jobs, the innovating executive behind such products as the iMac and iPhone, said in 2004 he had surgery for a tumor in the pancreas. He didn’t say whether he had the Whipple, which involves removing the bottom of the stomach, about half the pancreas, part of the bile duct, and some of the small intestine -- all of which can inhibit digestion. The goal is to rid the body of possible spreading cancer cells, called metastases.

“It’s considered one of the most complicated surgeries in the abdomen,” said Lo, who hasn’t treated Jobs and doesn’t know details of his condition. “You’re creating a big hole in that area, and then trying to connect everything back together.”

If the problem is dumping syndrome, the treatment may be a simple as a new diet, Lo said. Patients may be instructed to separate solid from liquid food, or eat more protein while avoiding fats and carbohydrates, he said.

Another option is to ask patients to eat numerous small meals rather than breakfast, lunch and dinner, Lo said. In some cases, doctors prescribe hormones, he said.

Jobs, in his statement today, said the remedy for his weight loss is “relatively simple and straightforward.”

Digestive Enzymes

Patients who undergo the Whipple frequently lack digestive enzymes that enable them to get nutrition from food, Lo said. Dumping syndrome, which also leads to weight loss, is believed linked to hormones, Lo said.

“It makes people very uncomfortable after they eat, and sometimes they’ll just avoid eating,” Lo said in an interview today.

Jobs, who turns 54 next month, said the reason for his weight loss “has been a mystery to me and my doctors.”

“After further testing, my doctors think they have found the cause -- a hormone imbalance that has been ‘robbing’ me of the proteins my body needs to be healthy,” he said in today’s statement.

Jobs is a vegetarian and is skeptical of mainstream medicine, Fortune reported last year. He delayed cancer surgery for nine months while he followed alternative treatments, the magazine reported in March.

Jobs, who co-founded Apple in 1976, said in a statement today that he lost weight throughout 2008. His decision to address his health follows months of speculation that he may have to hand the CEO job to Chief Operating Officer Tim Cook.

Board Statement

“If there ever comes a day when Steve wants to retire or for other reasons cannot continue to fulfill his duties as Apple’s CEO, you will know it,” Apple’s board said in a statement.

Steve Dowling, an Apple spokesman reached by telephone, said the company would have no comment beyond that supplied by Jobs and the board.

Jobs said in 2004 he had a rare form of pancreatic cancer. The most common form strikes more than 37,000 people in the U.S. annually, and kills most within a year, according to the U.S. National Cancer Institute.

Jobs said he had neuroendocrine islet cell tumor, which is diagnosed in fewer than 3,000 people yearly, according to pancreatica.org, the Web site of the Lorenzen Cancer Foundation in Monterey, California. When these tumors are diagnosed early and removed, patients may live 10 years or longer, Lo said.

Hormone Abnormalities

Neuroendocrine tumors may affect levels of a number of hormones, including insulin and glucagon that help control blood sugar levels, and somatostatin and gastrin that are involved in digestion and other functions, said Raji Annaswamy, an endocrinologist at Harvard Medical School in Boston who hasn’t treated Jobs and has no specific knowledge of his case.

“An imbalance in any of these hormones may lead to weight loss because of abnormalities in glucose and protein metabolism,” Annaswamy said in a telephone interview today.

In a 2004 e-mail, Jobs wrote, “I had a very rare form of pancreatic cancer called an islet cell neuroendocrine tumor.” The cancer, he said, “can be cured by surgical removal if diagnosed in time (mine was).”

Speculation about Jobs’s health resurfaced in June after he appeared thinner at Apple’s conference for developers. The company said at the time that he was suffering from a “common bug” and declined to elaborate. The speculation persisted as he continued to appear frail at company events. Investors punished the company’s shares with each report of Jobs’s ill health.

Apple, based in Cupertino, California, gained $3.83, or 4.2 percent, to $94.58 at 5:20 p.m. in Nasdaq Stock Market composite trading and has lost 47 percent in the past 12 months.

To contact the reporter on this story: John Lauerman in Boston at jlauerman@bloomberg.net.

Last Updated: January 5, 2009 17:26 EST