Waistlines of U.S. Adults Continue to Increase The prevalence of abdominal obesity and average waist circumference increased among U.S. adults from 1999 to 2012, according to a study in JAMA. 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), nonå_-Hispanic blacks (1.6 inch), and Mexican Americans (1.8 inch). The overall age-adjusted prevalence of abdominal obesity increased significantly from 46.4 percent in 1999-2000 to 54.2 percent in 2011-2012. Significant increases were present in men (37.1 percent to 43.5 percent), women (55.4 percent to 64.7 percent), non-Hispanic whites (45.8 percent to 53.8 percent), non-Hispanic blacks (52.4 percent to 60.9 percent), and Mexican Americans (48.1 percent to 57.4 percent).