There has not been significant change in the prevalence of obesity in the U.S., with data from 2009-2010 indicating that about one in three adults and one in six children and teens are obese; however, there have been increases in certain demographics, according to two studies being published by JAMA. The studies are being released online first because of their public health importance.
Katherine M. Flegal, Ph.D., Cynthia L. Ogden, Ph.D., M.R.P., and colleagues with the Centers for Disease Control and Prevention, Hyattsville, Md., analyzed data from the 2009-2010 National Health and Nutrition Examination Survey (NHANES) to determine rates of obesity in the U.S. In the analysis for prevalence among adults, rates of obesity (defined as a body mass index [BMI] of 30 or greater) were compared with data from 1999-2008. NHANES includes measured heights and weights for 5,926 adult men and women from a nationally representative sample of the U.S. population in 2009-2010 and for 22,847 men and women in 1999-2008.
In 2009-2010, the age-adjusted average BMI was 28.7 for men and women. The researchers found that overall, the age-adjusted obesity prevalence was 35.7 percent. Among men, the prevalence was 35.5 percent, and within race/ethnicity groups, prevalence ranged from 36.2 percent among non-Hispanic white men to 38.8 percent among non-Hispanic black men. There were significant increases in obesity for men over the period 1999-2000 through 2009-2010.
For women, the prevalence of obesity was 35.8 percent, and the range was from 32.2 percent among non-Hispanic white women to 58.5 percent among non-Hispanic black women. Over the period from 1999 through 2010, obesity showed no significant increase among women overall, but increases were statistically significant for non-Hispanic black women and Mexican American women. For both men and women, the most recent 2 years (2009-2010) did not differ significantly from the previous 6 years (2003-2008).
The age-adjusted prevalence of overweight and obesity combined (BMI 25 or greater) was 68.8 percent overall, 73.9 percent among men, and 63.7 percent among women.
"Obesity prevalence shows little change over the past 12 years, although the data are consistent with the possibility of slight increases," the authors write.
Among Children and Teens, Prevalence of Obesity is About 17 Percent
The examination of obesity among U.S. children and adolescents (birth through 19 years of age) included a representative sample (n = 4,111 [1,376 non-Hispanic white, 792 non-Hispanic black, and 1,660 Hispanic]) with measured heights and weights from NHANES 2009-2010. Among the measures analyzed were the prevalence of high weight-for-recumbent length (95th percentile or greater on the growth charts) among infants and toddlers from birth to 2 years of age and obesity (BMI 95th percentile or greater of the BMI-for-age growth charts) among children and adolescents ages 2 through 19 years. There were analyses of trends in obesity by sex and race/ethnicity, and analyses of trends in BMI within sex-specific age groups for 6 survey periods (every 2 years) from 1999 to 2010.
The researchers found that among children and adolescents ages 2 through 19 years, 16.9 percent were obese in 2009-2010 and 31.8 percent were either overweight or obese. The prevalence of obesity among males (18.6 percent) was significantly higher than among females (15.0 percent). There was no difference in obesity prevalence among males or females between 2007-2008 and 2009-2010, but there was a significant increase in prevalence between 1999-2000 and 2009-2010 (per 2-year survey cycle) in male children and adolescents but not in females. "Significant differences in obesity prevalence by race/ethnicity were found. In 2009-2010, 21.2 percent of Hispanic children and adolescents and 24.3 percent of non-Hispanic black children and adolescents were obese compared with 14.0 percent of non-Hispanic white children and adolescents."
The prevalence of high weight-for-recumbent length among infants and toddlers was 9.7 percent in 2009-2010. The prevalence did not change between 1999-2000 and 2009-2010. When the data from these time periods were analyzed together, there were significant differences by race/ethnicity, with Mexican Americans being significantly more likely to have high weight-for-recumbent length than non-Hispanic whites.
The authors also found that there was a significant increase in BMI among adolescent males ages 12 through 19 years but not among any other age group or among females.
"Many efforts both at the national level and at state and local levels focus on reducing childhood obesity. Yet results from NHANES indicate that the prevalence of childhood obesity in the United States remains unchanged at approximately 17 percent; although increases in obesity prevalence may he occurring among males," the researchers write.
Studies online: doi:10.1001/JAMA.2012.39 and doi:10.1001/JAMA.2012.40