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Obesity rates have stabilized, but our waistlines are still growing

Americans aren't getting fatter, but they're still adding inches around the waist

Americans may have stopped putting on pounds, but their waistlines are still expanding, according to a new analysis from the Centers for Disease Control and Prevention.

The average waist circumference of U.S. adults has increased by about 3% since the end of the last century. In 1999 and 2000, the waists of Americans who were at least 20 years old measured 37.6 inches (or 95.5 centimeters) around. By 2011 and 2012, that figure had grown to about 38.8 inches (98.5 cm), CDC researchers report in Wednesday’s edition of the Journal of the American Medical Assn.

Those figures are age-adjusted averages, but the trend applies to pretty much all demographic groups, the report says. Men and women both saw “significant increases” in waist circumference, as did “non-Hispanic whites, non-Hispanic blacks, and Mexican Americans.” Waistlines of Asian Americans may have grown too, but the CDC didn’t start collecting data on them as a group until 2011, the researchers note.

The study calls attention to five groups that experienced “particularly large increases” in waist circumference during the study period:

-- African American women in their 30s saw their average waist size grow by nearly 4.6 inches;   

-- Mexican American women who had passed their 70th birthday expanded their waists by 4.4 inches, on average;

-- Mexican American men in their 20s added an average of 3.4 inches to their waists;

-- Black men in their 30s grew their waists by about 3.2 inches, on average; and

-- White women in their 40s added an average of 2.6 inches to their waists.

Overall, the proportion of Americans suffering from abdominal obesity rose from 46.4% in 1999-2000 to 54.2% in 2011-2012, according to the study. (These figures were adjusted for age as well.)

The data on bigger waists come from the National Heath and Nutrition Examination Survey, an ongoing study that combines physical examinations with in-depth interviews.

Interestingly, NHANES data were cited in February by another group of CDC researchers who declared that American obesity rates have experienced “no significant changes” between 2003-2004 and 2011-2012. That study, which was also published in JAMA, focused on body mass index.

“At a time when the prevalence of obesity may have reached a plateau, the waistlines of U.S. adults continue to expand,” the new report concludes.

While BMI is used to assess whether a person has enough excess body fat to be considered overweight or obese, the waist circumference measurement can help doctors predict whether that extra weight translates into serious health problems.

“If most of your fat is around your waist rather than at your hips, you’re at a higher risk for heart disease and type 2 diabetes,” according to this explainer from the National Heart, Lung and Blood Institute, part of the National Institutes of Health. Those risks kick in for women with a waist size above 35 inches and men with a waist size above 40 inches.

To get an accurate measurement your own waist circumference, stand up, breath out and place a tape measure snugly around your bare abdomen, just above the top of your hip bones.

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