Contrary to previous evidence of what scientists have dubbed the "obesity paradox," being overweight or obese won't lower your risk of dying from a stroke, a new study shows.
The obesity paradox suggests that overweight, and even obese, people may have a lower risk of dying prematurely from a number of conditions, including stroke, than do normal-weight folks.
However, the new study suggests that the obesity paradox is likely a myth, since overweight and obese people were just as likely to die from a stroke as normal-weight people were. In addition, the study found that people who were overweight or obese were at least several years younger, on average, when they had a stroke than people who were a normal weight.
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"Stroke patients who were obese or overweight did not survive better than stroke patients who had normal weight," said lead researcher Dr. Tom Olsen, from the stroke unit at Frederiksberg University Hospital in Copenhagen, Denmark.
"Our study indeed shows that obese and overweight patients' risk of death after a stroke is not lower than that of normal-weight stroke patients. This means that we found no evidence of the obesity paradox in patients who had suffered a stroke," he added.
Olsen also noted that obese stroke patients were about six years younger than normal-weight stroke patients and, he added, "Overweight stroke patients were 2.3 years younger than the normal-weight stroke patients."
The report was published online June 2 in the journal JAMA Neurology.
Using the Danish registries of strokes and deaths, Olsen's team collected data on almost 72,000 people living in Denmark who'd had a stroke between 2003 and 2012. Information was available on weight, age, type of stroke and the severity of the stroke for nearly 54,000 people.
The average age among those who'd had a stroke was 71.8 years. Among those whose weight was available, 9.7 percent were underweight, 39 percent were normal weight, 34.5 percent were overweight and 16.8 percent were obese, according to the study.
Eleven percent died within the first month. Stroke accounted for 70 percent of the deaths.
The researchers found that people who were heavier tended to have strokes at younger ages than those who were normal weight -- approximately three years earlier for those who were overweight and six years sooner for obese people, according to the study.
The researchers suggest that one of the reasons they were able to dispel the obesity paradox was that they only looked at people they knew had died from stroke.
"All other studies on the issue of the obesity paradox also include deaths by other causes than of the stroke for which they were admitted to hospitals. By doing this, they cannot properly account for the severity of the stroke in the obese and overweight patients," Olsen noted.
One reason the paradox may have seemed real is that obese patients tend to have less severe strokes than normal-weight patients, according to the study.
"It is no wonder that it looks like it is better to be obese -- risk of death is of course lower in obese stroke patients, because their strokes are less severe," said Olsen.
However, when the researchers compared obese and normal-weight stroke patients, and then adjusted for differences in stroke severity, survival was no better for obese stroke patients than for normal-weight stroke patients, Olsen said.
"If you want to postpone stroke as much as possible, stay normal weight," advised Olsen.
Dr. Ralph Sacco, chairman of neurology at the University of Miami Miller School of Medicine, said, "This large study helps refute the obesity paradox that has been suggested in prior studies."
"Maintaining an ideal weight through diet and exercise is just as important for the brain as it is for the heart," he said.
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Dr. Koto Ishida, an assistant professor in the department of neurology at NYU Langone Medical Center in New York City, said there's "no evidence that there is a benefit to being obese, so it's clear to me that people should be striving for a normal weight."