A Study Sheds Light on the 'Obesity Paradox’ and Whether Being Overweight Protects Against Heart Disease
Being overweight or obese markedly increases the risk of heart disease.
By Jessica Migala
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Some data suggest a puzzling concept: If you carry extra weight, you may be more likely to recover from illness than a normal-weight or underweight person, and therefore have a lower relative risk of early death. It’s called the obesity paradox, and it’s one of the arguments used when discussing the flaws of body mass index (BMI), which defines obesity and is tied to health risk.
While the debate over the theory and BMI rages on, a new analysis suggests that at least when it comes to preventing heart disease, having a healthy weight could be critical for maintaining a long, healthy life.
The research, published in February 2019 inJAMA Cardiology, found that people who were obese had a greater risk of cardiovascular disease compared with people who had a normal weight. “They also had a shorter health and lifespan, meaning they had a shorter overall survival but spent more years living with cardiovascular disease,” explains the study's lead author, Sadiya S. Khan, MD, an assistant professor of medicine in cardiology at Northwestern University's Feinberg School of Medicine in Evanston, Illinois.
Specifically, middle-aged men and women who were obese had 67 and 85 percent, respectively, higher chances of cardiovascular disease compared with normal-weight folks. For those who were overweight, that risk for men and women was 21 and 32, respectively.
RELATED:What’s a Healthy BMI in Adults? Here’s Everything You Need to Know
How Study Authors Conducted the Research
The researchers pulled data from the Cardiovascular Disease Lifetime Risk Pooling Project. The authors looked at 10 studies of nearly 200,000 healthy people over 50 years who had no cardiovascular disease when the studies began. Researchers then calculated heart disease risks based on BMI — a measure of body fat calculated by using weight and height — divided by age and sex. (A BMI of under 18.5 is underweight; a BMI of 18.5 to 24.9 is normal; 25 to 29.9 is overweight; and 30 or more is considered obese, according to the National Institutes of Health.)
The findings confirmed their suspicions. “Given the adverse consequences of excess weight, we expected to see increased risk of cardiovascular disease,” Dr. Khan says. But she notes that what they wanted to discover was the degree to which being overweight and obese affects heart disease risk, and how long people live with the burden of these conditions.
Certainly, BMI has its own limitations, the Centers for Disease Control and Prevention (CDC) points out. While it can provide a general idea of how much body fat someone carries, it can’t definitively tell someone if they’re healthy or not.
BMI is generally better used as a measure of a population’s health than an individual’s. The authors note that one limitation of their study is they didn’t account for changes in BMI during follow-up years, and the BMI figure doesn't tell researchers where fat is located (how much is the dangerous visceral fat, for instance). Visceral fat is closely tied to disease risk.
RELATED:Why BMI Is Flawed and the History Behind How the Scale Came to Define Obesity
What the Study Results Suggest About the Legitimacy of the Obesity Paradox
The recent findings seem to call the obesity paradox into question, but there are a number of factors in play.
“Previous studies have shown that mortality isn’t typically increased in people with BMI in the overweight range but is increased in people with BMI in the obese range,” says William S. Yancy, MD, the director of the Duke University Diet and Fitness Center in Durham, North Carolina, who wasn’t involved in the study. “This makes some people question whether overweight is a true health issue, and in fact, in certain acute conditions — like pneumonia or major surgery — [being overweight] may be protective compared with a normal BMI,” he adds.
As the authors concluded, being “overweight does not appear to be associated with significantly greater longevity, and there is greater burden of [cardiovascular disease] during that lifespan,” noting that the obesity paradox seems to be caused by earlier diagnosis in these groups. This leads “to unclear messaging about the true risks of being overweight,” they said.
What Still Isn’t Known About the Relationship Between Weight and Heart Health
In the future, Khan says more studies are needed to pinpoint the best ways to maintain a healthy BMI, either individually or in large populations. But this study largely builds on what clinicians have been urging their patients to do — and that’s to maintain a healthy BMI, Khan says. Along with that, at-risk groups should also focus on what they can do to lower their risk of heart disease. Following tried-and-true health advice — including eating well and exercising regularly — can help prevent heart disease, according to the .
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