The prevalence of abdominal obesity and average waist circumference increased among U.S. adults from 1999 to 2012, according to a study in the September 17 issue of JAMA.

Waist circumference is a simple measure of total and intra-abdominal body fat. Although the prevalence of abdominal obesity has increased in the U.S. through 2008, its trend in recent years has not been known, according to background information in the article.

Earl S. Ford, MD, MPH, of the U.S. Centers for Disease Control and Prevention, Atlanta, and colleagues used data from seven 2-year cycles of the National Health and Nutrition Examination Survey (NHANES) starting with 1999-2000 and concluding with 2011-2012 to determine trends in average waist circumference and prevalence of abdominal obesity among adults in the U.S. Abdominal obesity was defined as a waist circumference greater than 40.2 inches (102 cm) in men and greater than 34.6 inches (88 cm) in women.

Data from 32,816 men and non-pregnant women ages 20 years or older were analyzed. The overall age-adjusted average waist circumference increased progressively and significantly, from 37.6 inches in 1999-2000 to 38.8 inches in 2011-2012. Significant increases occurred in men (0.8 inch), women (1.5 inch), non-Hispanic whites (1.2 inch), non-¬Hispanic blacks (1.6 inch) and Mexican Americans (1.8 inch).

The overall age-adjusted prevalence of abdominal obesity increased significantly from 46.4% in 1999-2000 to 54.2% in 2011-2012. Significant increases were present in men (37.1% to 43.5%), women (55.4% to 64.7%), non-Hispanic whites (45.8% to 53.8%), non-Hispanic blacks (52.4% to 60.9%) and Mexican Americans (48.1% to 57.4%).

The authors wrote that previous analyses of data from NHANES showed the prevalence of obesity calculated from body mass index (BMI) did not change significantly from 2003-2004 to 2011-2012. “In contrast, our analyses using data from the same surveys indicate that the prevalence of abdominal obesity is still increasing. 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 disruptors, and certain medications, have been proposed as potential explanations.”

“Our results support the routine measurement of waist circumference in clinical care consistent with current recommendations as a key step in initiating the prevention, control and management of obesity among patients.”