About 40% of U.S. adults were obese in 2015-2016, up from 34% in 2007-2008, according to a study reported online today in the Journal of the American Medical Association. About 8% of adults were severely obese, up from 6% in 2007-2008. Obesity increased among women and in adults aged 40 and older, while severe obesity increased in both men and women and adults under 60. Almost 19% of youth were obese in 2015-2016, about the same as in 2007-2008. Among adults aged 20 and older, obesity was defined as a body mass index of 30 or more, and severe obesity a BMI of 40 or more. The findings are based on data from the National Health and Nutrition Examination Survey.