Memorandum

CDC releases latest NHANES obesity prevalence data at 37% among US adults between 2011-2014 – November 13, 2015

Executive Highlights

  • CDC released new NHANES obesity prevalence data for 2011-2014 yesterday, demonstrating that prevalence was at 37% among US adults and 17% among US youth.
  • In the overall adult population, prevalence was higher in women than in men (38% vs. 34%) and was highest in middle-aged adults (40%); additionally, prevalence in non-Hispanic blacks (48%) and Hispanics (43%) was significantly greater than in non-Hispanic whites (35%) and non-Hispanic Asians (12%).

Yesterday, CDC released new NHANES obesity prevalence data for 2011-2014. The data demonstrated that during this time period, the prevalence of obesity was 37% among US adults and 17% among US youth. By sex, the prevalence was higher in women than in men (38% vs. 34%), although no sex difference was seen in youth. With regards to age, middle-aged adults (aged 40-59 years) had the highest prevalence at 40% followed by older adults (aged ≥60 years) and younger adults (aged 20-39 years) at prevalence rates of 37% and 32%, respectively; similar age patterns were shown in both men and women. Notably but unsurprisingly, prevalence varied significantly among racial groups: prevalence was highest in non-Hispanic black adults (48%), followed by Hispanic (43%), non-Hispanic white (35%), and non-Hispanic Asian adults (12%). The overall adult population’s pattern with higher prevalence in women was similar in non-Hispanic black and Hispanic groups. This trend in women is likely driven by physiological factors but also cultural factors, as weight stigma seems to disproportionately affect women.

As for youth data, adolescents (aged 12-19 years) had the highest prevalence at 21% compared to school-aged children (aged 6-11 years) at 18% and preschool-aged children (aged 2-5 years) at 9%, similar in both males and females. By race, the prevalence in non-Hispanic white youth (15%) was lower than in non-Hispanic black (20%) and Hispanic youth (22%), with no significant difference between non-Hispanic blacks and Hispanics. Again, non-Hispanic Asian youth had the lowest prevalence at 9%. In both adults and youth, these differences between whites and minority groups represent key inequities (see recent research on growing disparities in childhood obesity), reminding us of the importance to not solely examine the national average with regards to prevalence. We see the faster growth in prevalence in certain racial groups as a call for interdisciplinary efforts to examine the physiological, cultural, and social determinants affecting these different populations to provide first steps on implementing more targeted screening and prevention efforts – we saw similar findings in the latest diabetes prevalence statistics as well. For more analyses and insights, please see below.

  • While not statistically significant, obesity prevalence in adults increased from 35% to 38% between 2011-2012 and 2013-2014. This is certainly disappointing news amidst recent greater pushes for greater obesity prevention and hopeful data around lower calorie consumption – see the New York Times’ thoughts on the trend. Other than slight declines between 2005-2006 and 2007-2008 as well as 2009-2010 and 2011-2012, adult obesity prevalence remains on a steady increasing trend, as long-term comparisons from 1999-2014 demonstrate a significant increase from 31% to 38% - see the figure below for more details. While some may argue that prevalence has stabilized more over recent years, these high numbers still sound a very shrill alarm in our ears as they signal that current public health efforts are not enough. We are not looking to see these data plateau, but rather decrease. We may have made some (minor) movement on messaging around food and sugar-sweetened beverages, but clearly more needs to be done with regards to nutritional education and on interventions around physical activity . In addition, these new data did not break out various obesity classes, but we remain concerned about how more severe forms of obesity are growing with very limited treatment options when prevention efforts may not be enough.
  • The obesity prevalence in youth slightly increased between 2011-2012 and 2013-2014 from 16.9% to 17.2% but not as much as in adults. The smoother plateaus we see in children perhaps represent some of the significant messaging and media presence around First Lady Michelle Obama’s work. Of course, rates remain very high and are not yet declining according to these findings, again signaling the need that efforts are not adequate. However, we see it worthwhile to examine the public health interventions implemented in this population and see it translated to adults. Specifically, we would suspect that adults with no children may be most vulnerable, as they are likely the furthest removed from the public health messaging targeted toward youth.
  • In addition, CDC’s report highlighted that obesity is defined by BMI cut points in this data set, which may miss out on other risk factors for morbidity and mortality. The report specifically notes that such risk factors in Asian subgroups may begin at lower BMIs – a point that the ADA recently incorporated into its new Standards of Medical Care regarding diabetes screening. Certainly, this brings to light the complexity and issues with defining obesity based solely on BMI. However given BMI’s easy-to-use formulation and NHANES’ large dataset, we don’t see such “gold standards” of population-level data moving away from BMI. But we hope to see this message of needing more nuanced risk assessments (i.e. waist-to-hip ratio) applied in more individualized clinical interventions by providers.

Figure 1: Trends in obesity prevalence.

 

-- by Melissa An, Sarah Odeh, and Kelly Close