The number of U.S. men and women with the kind of obesity that settles around the waist – which can indicate a greater risk of ailments such as diabetes and heart disease – has risen sharply over the last 12 years, a recent study says.
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The study, conducted by researchers from the Centers for Disease Control (CDC) in Atlanta, found that in 2012, 54 percent of U.S. adults had abdominal obesity, up 46 percent in 1999.
A simple way to evaluate abdominal obesity in the clinic is to measure waist circumference. The researchers found that in the 12 years of data studied, the average waist size in the United States grew from 36 inches to 38 inches for women and from 34 inches to 40 inches for men.
Size can indicate health risks
Abdominal obesity is a waistline of more than 35 inches for women and more than 40 inches for men.
The trend was stronger among women. By 2012, the study found about two-thirds of all women had abdominal obesity, up from about half in 1999-2000. For men, about 44 had abdominal obesity, up from 37 percent in 1999-2000.
The size of your waistline tells you more than just what size pants you should wear, says endocrinologist Bartolome Burguera, MD. Dr. Burguera, director of obesity programs at Cleveland Clinic, did not take part in the study.
In recent years, physicians have become aware of the increased danger posed by abdominal fat – the fat that accumulates beneath the abdominal wall and gives you a pot belly or makes you apple-shaped.
These intra-abdominal fat cells are metabolically active, and release at least 80 different chemicals and hormones that promote diabetes, inflammation and lipid changes.
“It gives you an idea of your abdominal fat – the one that increases your risk of having diabetes, heart disease, high cholesterol, and that’s very important,” Dr. Burguera says. “We need to know that if that has increased, because that increases your risk of having a heart attack.
BMI obesity levels have plateaued
Earlier, separate research using the same data found that obesity levels, as measured by body-mass index (BMI), have changed little. About 35 percent of U.S. adults are obese, a number that has not changed much in recent years.
Those surveys define obesity as a BMI of at least 30. Someone who stands 5 feet, 4 inches tall would be considered obese if he or she weighs 175 pounds.
The researchers could not offer evidence to explain why the incidence of obesity determined by BMI calculation remains about the same while waist circumferences are rising. They say several factors may explain the discrepancy, such as sleep deprivation, lack of physical activity, endocrine disruptors, and certain medications.
The CDC researchers argue in the new study that their findings of expanding waistlines should prompt doctors to routinely measure their patients’ waist circumference “as a key step” in preventing, controlling and managing obesity.
“This paper is very good because it brings up the issue that we are not winning the battle,” Dr. Burguera says. “We really need to be more aggressive taking care of people with obesity and we need to also measure their abdominal circumference. If we just evaluate obesity and its associated cardiovascular risk based on BMI, we could miss the full picture.”
The researchers used information compiled for the National Health and Nutrition Examination Survey between 1999 and 2012. The participants were all older than age 20, with the average age being 45.
The Journal of the American Medical Association published the study, Trends in Mean Waist Circumference and Abdominal Obesity Among U.S. Adults, 1999-2012.