Chicago ? Obesity surgery helps patients do more than shed weight — it often cures their diabetes, high blood pressure and high cholesterol, researchers say.

The research, an analysis of 136 studies, found that such operations are more than cosmetic. They appear to alter the patient’s body chemistry itself and eliminate or relieve conditions that can lead to heart attacks, strokes and kidney failure.

The analysis was funded by a Johnson & Johnson Co. subsidiary that develops and markets surgical instruments, including staplers for obesity surgery. But the results echo what many doctors have reported seeing.

Diabetes was eliminated in nearly 77 percent of the affected patients; high blood pressure was eliminated in nearly 62 percent; cholesterol improved in at least 70 percent; and obstructive sleep apnea — episodes when breathing stops during sleep — disappeared in almost 86 percent. All four conditions are strongly linked to obesity and can have lethal consequences.

The study appears in today’s Journal of the American Medical Assn.

University of Minnesota surgeon Dr. Henry Buchwald, the study’s lead author and a consultant to the Johnson & Johnson subsidiary, said there was evidence that when the intestinal tract was rearranged in obesity surgery, patients who were diabetic are “cured” even before they start shedding significant amounts of weight.

That may be because such operations alter the intestinal hormones, he said.

Also, doctors have long known that losing weight helps improve blood pressure and cholesterol levels by reducing stress on the cardiovascular system.

About two-thirds of U.S. adults are overweight, and of those, almost half are grossly overweight, or obese. Surgery in which the stomach is reduced or restricted is typically reserved for extremely obese people who are at least 100 pounds heavier than their recommended weight and for whom other weight-loss methods have failed.

Buchwald and colleagues reviewed studies on obesity surgery published in English between 1990 and 2003. The studies involved 22,094 patients ages 16 to 64, at least two-thirds of them women.

The researchers found patients lost an average of 61 percent of their excess weight.

The most common U.S. obesity surgery, gastric bypass, involves creating an egg-sized pouch in the upper stomach and attaching it to a section of intestine. The procedure reduces the amount of food patients can eat and results in less food being absorbed. The researchers found it resulted in a 62 percent loss of excess weight.

Obesity surgery is a major operation, not cosmetic tinkering, Buchwald emphasized. The risks include malnutrition, stomach problems, infections and, in rare cases, death.