Think you're thin just because your BMI says so? Think again.
Well, you may look thin, but there's a chance you have what's called central obesity — fat centered in your abdominal area. Central obesity doesn't necessarily mean you weigh too much or your body mass index (BMI) is high, but it could mean you face even greater health risks than obese or overweight people whose fat isn't centered in their stomachs, a new study found.
When you hear the term "skinny fat" used, somewhat insensitively, to describe someone, this is likely what the speaker is referring to. And this new study found that being "skinny fat" could mean your health is at risk.
"We've been aware for a while that central obesity in patients carries a higher risk of cardiovascular events, but this paper shows that even comparing patients who are equally overweight, if you have central obesity, you're likely to do worse," said Jeffrey M. Schussler, MD, of Baylor Heart and Vascular Hospital and Baylor University Medical Center at Dallas, TX, in an interview with dailyRx News.
Dr. Schussler, who was not involved with the current study, added, "It's not clear why some patients tend to carry their weight in their midsection, but it's likely genetic."
Lead study author Francisco Lopez-Jimenez, MD, of the Division of Cardiovascular Diseases at the Mayo Clinic, and colleagues looked at 15,184 adults for over 14 years. Those who had central obesity but normal BMI were the most likely to die during the study period — around twice as likely as obese patients with more even fat distribution.
This finding may represent the "obesity paradox," wrote Paul Poirier, MD, PhD, of the Institut Universitaire de Cardiologie et de Pneumologie de Quebec in Canada, in an editorial about this study. The paradox is this: Obese patients have a raised risk of heart disease, but obese patients with heart disease are more likely to survive than normal-weight patients with heart disease.
Researchers have known for some time that centrally located fat poses health risks, but they had never before looked at overall survival of patients with normal BMIs and central obesity.
Currently, the gold standard for measuring patients' body fat is BMI, a number derived from height and weight. But if central obesity presents a health risk, as Dr. Lopez-Jimenez and colleagues found, then there's a problem: BMI doesn't measure where body fat is located on the body.
If you're worried you may have central obesity, you could theoretically have your body fat measured using computerized imaging techniques like CT scans and MRIs. But, as Harvard Medical School notes on its website, those procedures are expensive and equipment-heavy.
Of course, you could always do what Dr. Lopez-Jimenez and team did to see whether study patients were at risk of central obesity: Measure your waist-to-hip ratio.
Here's how Harvard says to do it: "With your abdomen relaxed, measure your waist at the navel. Next, measure your hips at their widest point, usually at the bony prominences. Finally, divide your waist size by your hip size: Waist (in inches) / Hips (in inches) = ratio." Then, check your number on a waist-to-hip ratio chart to see where you stand.
Although your risk of carrying fat around your midsection is likely genetic, you can still take some healthy steps, Dr. Schussler said.
"Other than choosing your parents wisely, patients should watch their calorie intake and make sure they exercise regularly," he said.
The study and editorial were published online Nov. 9 in the Annals of Internal Medicine.
The National Institutes of Health, American Heart Association, European Regional Development Fund and Czech Ministry of Health funded this research. Potential conflicts of interest included funds from GlaxoSmithKline, Philips Respironics and U-Health, among others.