Carrying extra pounds doesn't necessarily mean your heart is ailing, according to Greek researchers.
They found less than 10 percent of healthy obese people in their 50s and 60s without risk factors for heart disease went on to develop heart failure over six years.
By contrast, 16 percent of their slimmer peers, also without the suite of risk factors known as metabolic syndrome, ended up with the debilitating condition.
The new study, in the Journal of the American College of Cardiology, adds to a growing body of evidence suggesting that fat people aren't always unhealthy.
But that doesn't mean they get a free pass to gorge on cheeseburgers and French fries, researchers warn, because the extra weight may take a toll down the road.
"At an older age, they probably are no longer healthy," Dr. Eileen Hsich, of the Cleveland Clinic in Ohio, points out in an editorial about the Greek findings.
What's more, the new study was based on people who had no signs of heart disease or diabetes to begin with, and so might not represent the majority of heavy people.
Dr. Christina Voulgari at Athens University Medical School and colleagues followed 550 men and women, a quarter of whom were obese. Participants averaged about 55 years old.
More than two-thirds of obese individuals harbored risk factors for heart and blood vessel disease, such as high fat levels in the blood, low "good" cholesterol, high blood pressure, insulin resistance and a large waistline -- collectively referred to as "metabolic syndrome."
By comparison, only a little more than a third of normal-weight individuals did.
Whether or not a person was obese had little impact, though, on his or her risk of heart failure, in which the heart muscle weakens and cannot supply enough oxygen-rich blood to the body. The most common cause of heart failure is clogged vessels supplying inadequate blood to the heart.
But metabolic syndrome made a big difference in who experienced heart failure, even after accounting for smoking, physical activity and other factors tied to heart disease.
For instance, 63 percent of normal-weight people with metabolic syndrome developed heart failure, compared with 16 percent of those without the syndrome.
"Being normal weight does not necessarily mean that we are healthy," Voulgari told Reuters Health in an e-mail.
She said she got the idea for the study when her mother asked her how come one of her obese friends didn't have heart problems, while Voulgari's mother did.
As it turned out, Voulgari added, heavy people actually had fewer cases of heart failure than their normal-weight and obese peers.
Among obese participants with metabolic syndrome, 54 percent developed the problem, whereas only nine percent of those without metabolic syndrome did.
About five million Americans have heart failure, and the condition contributes to some 300,000 deaths a year, according to the National Heart, Lung, and Blood Institute.
Voulgari said her study doesn't mean people without metabolic syndrome should eat fast food without worrying about the consequences. Instead, it suggests everybody should aim for a healthier lifestyle.
"We should try to focus more on exercise, follow the 10,000-steps-daily rule, follow a healthier lifestyle and not smoke to stay in shape," she said.
She added that eating a Mediterranean diet, which has been tied to heart benefits, is also a good idea. The diet includes olive oil and plenty of fruits and vegetables, legumes, whole grains, fish and moderate amounts of red wine.