The prevalence of obesity in 2013-2014 was 35% among men and 40% among women, and between 2005 and 2014, there was an increase in prevalence among women, but not men, researchers said.
To get a comprehensive understanding of the trends in obesity, Katherine M Flegal, of the National Center for Health Statistics, Centres for Disease Control and Prevention and colleagues examined obesity prevalence for 2013-2014 and trends over the decade from 2005 through 2014, adjusting for sex, age, race/Hispanic origin, smoking status and education.
The researchers analysed data obtained from the National Health and Nutrition Examination Survey (NHANES), a cross-sectional, nationally representative health examination survey of the US civilian population that includes measured weight and height. The analysis included data from 2,638 adult men (average age, 47 years) and 2,817 women (average age, 48 years) from the most recent 2 years (2013-2014) of NHANES and data from 21,013 participants in previous NHANES surveys from 2005 through 2012.
For the years 2013-2014, the overall age-adjusted prevalence of obesity (body mass index [BMI] 30 or greater) was 38%; among men, it was 35%; and among women, it was 40%. The corresponding prevalence of class 3 (BMI 40 or greater) obesity overall was 7.7%; among men, it was 5.5%; and among women, it was 9.9%.
Analyses of changes over the decade from 2005 through 2014, adjusted for age, race/Hispanic origin, smoking status, and education, showed significant increasing linear trends among women for overall obesity and for class 3 obesity but not among men. Analyses of the data from 2013-2014 found that for men, obesity prevalence varied by smoking status, with the prevalence of obesity significantly lower among current smokers than among never smokers. For women, there were no major differences by smoking status, but those with education beyond high school were significantly less likely to be obese.
Researchers said that although there has been considerable speculation about the causes of the increases in obesity prevalence, data are lacking to show the causes of these trends, and there are few data to indicate reasons that these trends might accelerate, stop, or slow. "Other studies are needed to determine the reasons for these trends," they said.
The research was published in the Journal of the American Medical Association.
