Measure Those Waistlines: They Are Expanding

American adults are getting bigger around the middle, even as the prevalence of obesity may have reached a plateau, a study has shown.

In an analysis of data from the National Health and Nutrition Examination Survey, Earl S. Ford, MD, MPH, from the Centers for Disease Control and Prevention, Atlanta, Georgia, and colleagues found that the prevalence of abdominal obesity and average waist circumference increased progressively and significantly in US adults overall, as well as in specific subpopulations, between 1999 and 2012. The authors present their results in a letter published in the September 17 issue of JAMA.

The overall age-adjusted mean waist circumference of the study population, which included 32,816 men and nonpregnant women aged 20 years or older, rose from 95.5 cm (95% confidence interval [CI], 94.2 - 96.8 cm) in 1999 to 2000 to 98.5 cm (95% CI, 97.5 - 99.4 cm) in 2011 to 2012.

Significant increases occurred in men, women, non-Hispanic whites, non-Hispanic blacks, and Mexican Americans. Non-Hispanic black women aged 30 to 39 years had the largest increase at 11.6 cm, followed by 11.2 cm for Mexican American women aged 70 years or older, 8.7 cm for Mexican American men aged 20 to 29 years, 8.1 cm for non-Hispanic black men aged 30 to 39 years, and 6.6 cm for non-Hispanic white women aged 40 to 49 years.

The overall age-adjusted prevalence of abdominal obesity, defined as a waist circumference greater than 102 cm in men and greater than 88 cm in women, increased significantly as well, going from 46.4% (95% CI, 42.1% - 50.8%) in 1999 to 2000 to 54.2% (95% CI, 51.3% - 57.0%) in 2011 to 2012.

Previous analyses of National Health and Nutrition Examination Survey data show no significant change in the prevalence of obesity calculated from body mass index from 2003-2004 to 2011-2012. However, when Dr. Ford and colleagues restricted their study to that period, the current analysis still showed significant increases in mean waist circumference among all adults, women, non-Hispanic blacks, and Mexican Americans. Those findings suggest the possible influence of additional lifestyle and metabolic factors on waistline expansion, according to the authors.

"The reasons for increases in waist circumference in excess of what would be expected from changes in BMI remain speculative, but several factors, including sleep deprivation, endocrine disrupters, and certain medications, have been proposed as potential explanations," they write.

"At a time when the prevalence of obesity may have reached a plateau, the waistlines of US adults continue to expand," the authors observe. These results, they note, "support the routine measurement of waist circumference in clinical care consistent with the current recommendations as a key step in initiating the prevention, control, and management of obesity among patients."

The authors have disclosed no relevant financial relationships.

JAMA. 2014;312;1151-1153. Extract

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