It's called the obesity paradox, and a new review of the research shows that it is real.
Study after study has shown that obese heart patients have better survival and have fewer strokes and heart attacks than normal-weight or underweight heart patients with the same severity of disease, says cardiologist Carl J. Lavie, MD, of the Ochsner Medical Center in New Orleans.
"Even now a lot of cardiologists haven't heard of this or don't believe it," he tells WebMD. "But it is clear that as a population, obese patients with heart disease respond well to treatment and have paradoxically better outcomes than thinner patients."
Obesity Leading Cause of Heart Death
Just to be clear, no one is saying that being overweight is good for your heart. It is not.
In fact, obesity is poised to overtake smoking as the leading cause of preventable death in the U.S., and the majority of those deaths will be directly or indirectly linked to cardiovascular disease.
More than two-thirds of adults in the U.S. are now overweight or obese. Lavie says that if the trend continues the nation may soon see a decline in life expectancy for the first time in decades.
Compared to lean people, overweight and obese people have a much higher incidence of heart attacks, strokes, and death from other cardiovascular causes.
But when normal or underweight people get heart disease, the studies show that their prognosis is worse than heart patients who carry extra pounds.
Lavie's review of this phenomenon encompassed research involving hundreds of thousands of patients. The findings appear in the May issue of the Journal of the American College of Cardiology.
Searching for Clues to Obesity Paradox
So if the obesity paradox really does exist in patients with heart disease, what explains it?
There are many theories, but Lavie says the answer is probably not simple.
It could be that lean heart patients have more aggressive disease because they are genetically predisposed to develop heart disease and have worse outcomes, he says.
Obese people may also be diagnosed and placed on treatment earlier in the course of their disease because symptoms closely linked to obesity -- such as becoming easily winded -- are similar to those seen with heart disease.
But there is also some evidence, mostly from animal studies, suggesting a direct protective benefit for obesity, UCLA professor of cardiology and obesity paradox researcher Gregg C. Fonarow, MD, tells WebMD.
If such a benefit is proven, Fonarow says it could have profound implications for the management of overweight and obese heart patients.
"We will have to ask ourselves if uniformly recommending weight loss in these individuals is advisable," he says. "It may be that we can't take the body weight standards for a healthy population and automatically apply them to people with cardiovascular disease."
But Lavie says studies suggest that weight loss improves outcomes among obese heart patients.
"Overweight heart patients do better than thin patients, but overweight patients who lose weight do best of all," he says.
Studies also show that whether patients lose weight or not, engaging in regular exercise is one of the best things they can do for their hearts.
Fonarow says the obesity paradox should reassure obese patients with heart disease who have tried to lose weight and failed.
"These patients often feel that there is nothing they can do to turn things around, but if they take their medication and stay physically active their prognosis is actually very good," he says.