The American health care system is overweight, undisciplined and feverish and must curb its "conspicuous consumption" to avoid rationing of services, warns a leading expert on health care.

"We have too many hospitals, too many beds, too much duplication and competition, and too much waste," said Dr. Robert G. Petersdorf, dean of the School of Medicine at the University of California at San Diego, in a recent speech at the George Washington University Medical Center.

The dangerous result of all this, he said, is that high-tech treatments could be available only to "those who can afford them" and be denied to others. "In this country, we should not find that an acceptable solution."

"Duplication of services is often motivated by nothing more than a drive for prestige and the preservation of the professional or administrative ego," said Petersdorf, a former professor of medicine at Yale, Johns Hopkins and the University of Washington.

He cited the case of a surgeon at a teaching hospital in southern California who proposed that the hospital embark on a liver transplantation program several years ago. Turned down, the surgeon peddled his plan to local community hospitals and finally persuaded two of them to start doing liver transplants.

"The results were disastrous," Petersdorf said. "Five of six patients died, two after a second transplant, and both hospitals suspended the program."

When San Diego recently announced plans for a county-wide network of trauma centers, almost every hospital in the county competed to be included, regardless of need.

"The consequence of this foolish and expensive competition has been that we have a highly sophisticated trauma system," Petersdorf said, "but because of the ambitions of a number of community hospitals and their staffs, we have far too many and the system will be far too costly."

He also questioned the need for nine hospitals in the District and Maryland to try to buy the latest generation of sophisticated, but costly, radiological technology called nuclear magnetic resonance (NMR).

"While there is a great tendency to introduce new technology into the health care system, there is a great hesitation to eliminate medical practices once they have become obsolete," he said, citing these examples:

*Kidney dialysis and transplantion. Dialysis became feasible in the 1960s for patients who otherwise would die of chronic kidney failure. The cost of the thrice-weekly treatments, which filter waste from the blood, can reach $25,000 a year. Medicare now covers that cost for about 63,000 dialysis patients, at a cost of more than $2 billion a year. The alternative is a kidney transplant, which not only frees the patient from continual dialysis, but is much less expensive in the long run. But a shortage of organ donors forces most patients to choose the more expensive dialysis.

Petersdorf said doctors should limit dialysis to patients under 75 and encourage home dialysis, which is cheaper. Organ procurement should be made more efficient to encourage kidney transplants, he said.

*Open-heart surgery. Coronary artery bypass surgery has become one of the most common -- and expensive -- operations in the United States. Between 1973 and 1982, the annual total of bypass operations jumped from 25,000 to 170,000 and is still rising, despite recent evidence that nonsurgical treatment is just as effective for some forms of coronary heart disease. Coronary bypass accounted for about $2.5 billion, or almost 1 percent, of the U.S. medical bill in 1982. The doctor glut. By 1990, every medical specialty and subspecialty will have a surplus, a federal advisory commission on medical education concluded recently. Paradoxically, that may raise costs, because doctors, not patients, determine most medical demand by admitting patients to the hospital and ordering tests and treatments. Petersdorf recommends reducing the number of students in each medical school "by a sizable number" and closing some medical schools that have opened in the past decade.

*The high cost of dying. Eighty percent of all deaths in the United States occur in hospitals or nursing homes, up from 50 percent 30 years ago. That reflects the increasingly intensive -- and expensive -- care of patients in the final months of life. Every hospital in the nation with at least 200 beds has an intensive care unit, where care is three to four times as expensive as in regular hospital units.

Petersdorf recommends more home care for the terminally ill, because "patients themselves would prefer to go out in their own beds and not in some strange place with tubes coming out of every orifice." Also, the need to keep permanently comatose patients alive at a cost of up to several thousand dollars a day must be "carefully questioned."

"We physicians are charged with prolonging life," he said, "but not with prolonging death."