WEDNESDAY, June 16 (HealthDayNews) -- The rapid removal of even large amounts of body fat via liposuction is no quick fix for obesity-related conditions like diabetes or cardiovascular disease, researchers say.

Surgeries that rid patients of an average 22 pounds of fat did nothing to change their insulin sensitivity, blood pressure readings or cholesterol levels, according to a study published in the June 17 issue of the New England Journal of Medicine.

"There was no sign that liposuction caused adverse health effects from a medical perspective, but patients didn't gain any benefit, either," said Dr. David E. Kelley, director of the Obesity Research Center at the University of Pittsburgh who wrote a commentary on the study for the journal.

According to the American Society of Plastic Surgeons, more than 320,000 liposuction procedures were performed last year in the United States. For most Americans, liposuction "is still perceived as a cosmetic procedure," Kelley said.

But fighting obesity can also help prevent killer diseases like diabetes and heart disease. "Fat affects metabolism, appetite, everything," Kelley said. "So the thought has always been, 'What would happen if we suddenly removed a very large portion of fat?'"

Now, researchers led by Dr. Samuel Klein of Washington University School of Medicine in St. Louis believe they've answered that question.

For their study, Klein and his colleagues used liposuction on 15 obese women to remove an unusually large amount of abdominal fat from each -- about 22 pounds on average, totaling nearly 20 percent of their total body fat. Eight of the patients were diagnosed with type 2 diabetes; the other seven showed no signs of the disease.

The researchers compared each woman's post-liposuction insulin sensitivity, blood pressure, cholesterol levels and other common disease risk factors to readings taken before surgery.

According to Klein, "none of those risk factors improved, despite removing these large amounts of fat."

So if liposuction doesn't affect disease risk factors, how does shedding fat by non-surgical means -- such as diet and exercise -- improve health?

The answer, Klein said, lies in the size of each fat cell.

"We think that when you lose fat by dieting, you undergo a negative energy balance, consuming fewer calories than you burn up. This causes your fat cells to shrink to a smaller size," Klein explained.

"But with liposuction, you remove fat cells without shrinking any of the remaining fat cells left behind," he said.

Those oversized, post-liposuction fat cells continue to act as they always have, raising blood pressure and straining the body's response to insulin.

On the other hand, "diets and exercise also cause you to reduce fat deep within your muscle tissue and liver," Klein said. "Inside of those tissues are lipid droplets that are associated with normal metabolism and insulin resistance. When you reduce fat via diet and exercise, you reduce the fat content in those non-fat tissues, too."

To the dismay of those hoping for a medical boost from fat-removing surgery, none of this occurred after liposuction.

"Unfortunately, we're back to the same old boring advice -- it's not how much fat you lose but how you lose it that's important," Klein said.

Losing fat the old-fashioned way, by eating sensibly and working out, "is key to improving your metabolic health," he added.

Still, liposuction's cosmetic results might give some patients the mental jump-start they need to eat better and get back on the treadmill.

"Some of the [health] benefit observed in previous studies with smaller amounts of liposuction had to do with the fact that people who had the procedure then began to change their lifestyle," Klein said.

More information

Get the skinny on liposuction from the American Society of Plastic Surgeons. But the U.S. Food and Drug Administration cautions you to also consider the risks.