Angeras' team found those with the lowest risk of dying after acute coronary syndrome were overweight and moderately obese, while the highest risk was among the underweight and the morbidly obese.
Conventional wisdom says losing weight improves health, but that may not be the case for obese people who have already developed heart disease, the researchers say.
"In acute coronary syndrome, the obesity paradox suggests that there could be protective mechanisms in either fat tissue or in obese patients' [individual makeup] that reduce the risk of mortality. This is of course speculative and needs further investigations," Angeras said.
"We believe that it is important to focus on secondary prevention like treating [high blood pressure] and [high fat levels in the blood], stop smoking, exercise and eat a healthy diet, which has solid evidence in literature," he added. "Weight reduction is, however, perhaps not that important in itself, more a cause of anxiety among patients."
Angeras added that the obesity paradox exists and should be recognized in health care guidelines for acute coronary syndrome.
Fonarow pointed out that multiple explanations and potential mechanisms have been advanced to explain the obesity paradox, but the exact mechanisms are not known and further studies are needed.
"Yet, patients who are obese present with acute coronary events at an age 8 to 10 years younger, compared with healthy and underweight individuals, [which] demonstrates the adverse consequences of obesity in developing cardiovascular events in the first place," Fonarow said.
And Katz added that there has long been evidence that the overall relationship between body weight and all-cause mortality, when plotted as a graph, takes the shape of a J or U, with lower mortality near the middle, and higher mortality at both the lowest and highest weights.
"But there is no paradox in this," Katz said. "Sick people lose weight, and the sickest people lose the most weight of all. Sometimes, this is the disease. Sometimes, it's the therapy -- such as cancer chemotherapy. And sometimes, it's an array of factors such as isolation, loneliness and despair. In contrast, people with a reserve of vitality, and hope, keep eating."
For more on obesity, visit the U.S. National Library of Medicine.
Copyright © 2012 HealthDay. All rights reserved.