A person with a body mass index (BMI) of 30 or greater is considered obese. BMI is calculated as weight in pounds divided by height in inches squared and multiplied by 703.
While obesity puts people at risk for a whole host of chronic illnesses, including heart disease, there's a least one situation in which extra pounds appear to provide a health advantage.
Oddly, once someone has already had a heart attack, obesity seems to confer protection against further heart problems, a new study suggests.
The results show that among 1,231 heart failure patients (those who have already had a heart attack), underweight, normal weight and overweight (but not obese) individuals had a 76 percent increase in risk of sudden cardiac death compared with obese patients.
Sudden cardiac death, which kills up to 330,000 Americans each year, occurs when the heart suddenly stops beating. This is different from a heart attack, which happens when blood flow to the heart is interrupted.
The findings, presented March 16 at the American College of Cardiology Annual Scientific Session, add to a growing body of research on this phenomenon, known as the "obesity paradox." Several studies have come to the same puzzling conclusion: Obese patients with heart disease seem to do better and live longer than skinnier patients.
The results even surprised the researchers. "When we started this study we were hoping the data would disprove the obesity paradox," said study author Bonnie Choy, a second-year medical student at the University of Rochester's School of Medicine and Dentistry.
And the findings held true even when they broke the data down and examined underweight, normal weight and overweight people in separate categories instead of lumping them all in one group, Choy said.
"We still the saw an inverse relationship between BMI and sudden cardiac death." BMI, or body mass index, is a ratio of weight to height, and is considered an indicator of how much body fat a person has. The researchers defined obese as someone with a BMI of 30 or greater.
No one knows why obesity seems to bring benefits in this case, though several ideas have been tossed around. For instance, it's possible that obese individuals have a genetic advantage when it comes to surviving heart failure, the University of Rochester researchers suggest.
"Obese patients are hard on their bodies; many don't eat right, don't exercise, and many smoke," said study researcher Eric Hansen, a second-year medical student at the University. "If their bodies are surviving this bad treatment then perhaps they are better equipped, from a genetic standpoint, to live with heart failure."
On the flip side, thinner people with heart disease might be genetically prone to developing heart problems, since their heart condition arose despite their weight.
In addition, other factors, like scarring from a previous heart attack, may cause more problems over the short term than obesity causes over the long term.
The students conducted the study with Dr. Ilan Goldenberg, a professor of cardiology.
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