June 21 (HealthDay News) -- In what doctors admit is a paradox, new European research shows that obese patients have half the risk of dying after a heart attack compared with normal-weight patients.

"Once a heart attack has occurred and been optimally treated, obese patients switch to a more favorable prognosis compared to normal-weight patients," said lead researcher Dr. Heinz Joachim Buettner, the head of interventional cardiology at Herz-Zentrum Bad Krozingen, Germany.

But the finding is no license for Americans to pile on the pounds, since obesity has long been known as a major factor for bringing on heart attack in the first place.

"Every effort should continue to prevent and treat obesity, and this study should not be taken to mean that it is good for one's health to be overweight or obese," said Dr. Gregg C. Fonarow, director of the Ahmanson-UCLA Cardiomyopathy Center at the University of California, Los Angeles.

He was not involved in the new study, which is published in the June 20 issue of the European Heart Journal.

In the study, Buettner's group tracked the health outcomes of almost 1,700 people who were hospitalized and treated for a common type of heart attack known as unstable angina/non-ST-segment elevation.

Among the patients, a third were normal weight, half were overweight, and 18 percent were either obese or very obese. The obese and very obese patients were by-in-large younger and more likely to have high blood pressure and diabetes.

In addition, for most of the obese patients, this was their first heart attack. They were also more likely to leave the hospital with prescriptions for heart medications, such as statins, ACE-inhibitors and beta-blockers.

During three years of follow-up, Buettner's team found that obese and very obese patients had less than half the risk of dying compared with normal weight patients. Among all the patients, 9.9 percent of normal-weight patients died, compared to 7.7 percent of overweight patients. However, only 3.6 percent of obese patients had died, and none of the very obese patients died.

How might obesity lessen risk for death after heart attack?

The reasons for the paradox remain unclear, but Fonarow speculates that obese people may have more biological resources to draw on than thinner people.

"Patients who are overweight and obese may be able to drawn on greater metabolic reserve than patients who are in the underweight or healthy weight categories," Fonarow said.

"We have previously published on an obesity paradox in patients with acute as well as chronic heart failure, so this paradox applies to a number of cardiovascular disease states," he added.

Buettner stressed that, despite these findings, staying slim dramatically lowers your risk for having a heart attack in the first place.

"It is well known that even a modest intentional weight loss can improve or prevent obesity-related cardiovascular risk factors like diabetes mellitus and arterial hypertension," he said. This means that "obese people have a great potential to influence their prognosis, and they should start the effort before an acute coronary event occurs," he added.

Fonarow agreed that becoming obese is definitely not a good way to protect yourself from having a heart attack or even dying after suffering one.

"The findings from this study further confirm the finding of a number of prior studies that demonstrated an obesity paradox exists in patients with established cardiovascular disease, including those presenting with acute coronary syndromes receiving therapy," he said.

However, even though obese patients with acute coronary syndrome had a lower risk of post-heart attack death, obesity strongly contributes to an increased risk of heart trouble, diabetes, and cardiovascular death, Fonarow added.

SOURCES: Heinz Joachim Buettner, M.D., head, interventional cardiology, Herz-Zentrum Bad Krozingen, Germany; Gregg C. Fonarow, M.D. professor, clinical medicine, director, Ahmanson-UCLA Cardiomyopathy Center, University of California, Los Angeles; June 20, 2007, European Heart Journal