April 24, 2018 Craig M. Hales, MD1; Cheryl D. Fryar, MSPH1; Margaret D. Carroll, MSPH1; et
alDavid S. Freedman, PhD2; Cynthia L. Ogden, PhD1
Obesity
prevalence has been increasing since the 1980s among adults, but among youth,
prevalence plateaued between 2005-2006 and 2013-2014.1,2 We analyzed trends in obesity
prevalence among US youth and adults between 2007-2008 and 2015-2016 in order
to determine recent changes.
Methods
The
National Health and Nutrition Examination Survey (NHANES) is a cross-sectional
survey with a complex, multistage probability design that represents the
civilian, noninstitutionalized population with a response rate of 75.4% in
2007-2008 and 58.7% in 2015-2016.3 Participants 18 years or older
provided written consent, youth aged 7 to 17 years provided written assent, and
parental permission was obtained in writing for youth younger than 18 years.
NHANES was approved by the National Center for Health Statistics research
ethics review board. Standardized measurements of weight and height were
obtained.3
Among
adults aged 20 years and older, obesity was defined as a body mass index (BMI;
calculated as weight in kilograms divided by height in meters squared) of 30 or
more and severe obesity was defined as a BMI of 40 or more.4 Among youth aged 2 to 19 years,
obesity was defined as a BMI at or above the 95th percentile of sex-specific
BMI-for-age and severe obesity was defined as a BMI at or above 120% of the
95th percentile.1 Pregnant females were excluded.
Prevalence
and 95% CIs of obesity and severe obesity were estimated overall5 and stratified by sex and age
(2-5, 6-11, 12-19, 20-39, 40-59, and ≥60 years). Linear and quadratic trends
overall and stratified by sex and age were examined in regression models with
2-year survey cycles modeled as an orthogonal polynomial and in adjusted models
(including survey cycle, sex, age, race/Hispanic origin [non-Hispanic white,
non-Hispanic black, Hispanic, or other], education [high school graduate or
less, some college, and college graduate; education of household head for
youth], and, among adults, smoking status [never, former, or current smoker])
to determine if trends could be explained by these factors. Interactions
between survey cycle with sex and age were tested among youth and adults
separately to supplement stratified analyses and were not significant. A
2-sided P value of .05 was used to assess statistical
significance.
Statistical
analyses accounted for the complex survey design, including examination sample
weights, which adjusted for nonresponse and took into account loss between the
screener and interview and between the interview and the examination. Analyses
were conducted using R (R statistics), version 3.4.16; SAS (SAS Institute), version 9.4; and
SUDAAN (RTI International), version 11.0.
Results
Data
from 16 875 youth (Table 1) and 27 449 adults (Table 2) were analyzed. Among youth, obesity
prevalence was 16.8% (95% CI, 14.2%-19.8%) in 2007-2008 and 18.5% (95% CI,
15.8%-21.3%) in 2015-2016. Based on the unadjusted model, there were no
significant linear trends in the prevalence of obesity or severe obesity
overall, by sex or age group (P range = .17 to .78) (Table 1). Obesity prevalence among children aged
2 to 5 years showed a quadratic trend (P = .04), decreasing from 10.1%
in 2007-2008 to 8.4% in 2011-2012 and then increasing to 13.9% in 2015-2016.
Adjusted overall linear and quadratic trends for obesity and severe obesity
among youth aged 2 to 19 years remained nonsignificant.
Age-standardized
prevalence of obesity among adults increased from 33.7% (95% CI, 31.5%-36.1%)
in 2007-2008 to 39.6% (95% CI, 36.1%-43.1%) in 2015-2016 (P = .001) (Table 2). Prevalence increased among women, and
in adults aged 40 to 59 years and 60 years or older. The observed increases in
men and adults aged 20 to 39 years did not reach statistical significance.
There were no significant quadratic trends. The adjusted model also showed a
significant overall linear trend for obesity among adults (P < .001;
data not shown).
Age-standardized
prevalence of severe obesity in adults increased from 5.7% (95% CI, 4.9%-6.7%)
in 2007-2008 to 7.7% (95% CI, 6.6%-8.9%) in 2015-2016 (P = .001).
Prevalence increased in men, women, and adults aged 20 to 39 years and 40 to 59
years. There was no significant linear trend among adults 60 years and older.
There were no significant quadratic trends. The adjusted model also showed a
significant overall linear trend for severe obesity (P < .001; data
not shown).
Discussion
Over
the most recent decade between 2007-2008 and 2015-2016, increases in obesity
and severe obesity prevalence persisted among adults, whereas there were no
overall significant trends among youth. Changes in demographics did not explain
the observed trends. Limitations include small sample sizes in the youngest age
group. Residual bias due to incomplete nonresponse adjustment is possible and
may vary with changing response rates. Additional NHANES data will allow
continued monitoring of trends in obesity and severe obesity prevalence among
US youth and adults.
Section
Editor: Jody W. Zylke, MD, Deputy Editor.
Article
Information
Accepted
for Publication: March 1, 2018.
Corresponding
Author: Craig M. Hales, MD, National Center for Health Statistics,
US Centers for Disease Control and Prevention, 3311 Toledo Rd, Hyattsville, MD
20782 (chales@cdc.gov).
Published
Online: March 23, 2018. doi:10.1001/jama.2018.3060
Author
Contributions: Dr Hales had full access to all of the data in the study
and takes responsibility for the integrity of the data and the accuracy of the
data analysis.
Concept
and design: Hales, Ogden.
Acquisition,
analysis, or interpretation of data: All authors.
Drafting
of the manuscript: Hales.
Critical
revision of the manuscript for important intellectual content: All
authors.
Statistical
analysis: Hales, Fryar, Carroll, Freedman.
Administrative,
technical, or material support: Hales.
Supervision: Ogden.
Conflict
of Interest Disclosures: All authors have completed and submitted
the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were
reported.
Disclaimer: The
findings and conclusions in this report are those of the authors and not
necessarily the official position of the US Centers for Disease Control and
Prevention (CDC).
Additional
Information: The National Center for Health Statistics and the CDC had
a role in the design and conduct of the National Health and Nutrition
Examination Survey, in the collection and management of the data, and in the
review and approval of the manuscript; however, the National Center for Health
Statistics and the CDC had no role in the analysis and interpretation of the
data, in the preparation of the manuscript, or in the decision to submit the manuscript
for publication.
References
1. Ogden
CL, Carroll MD, Lawman HG, et al. Trends in obesity
prevalence among children and adolescents in the United States, 1988-1994
through 2013-2014. JAMA. 2016;315(21):2292-2299.
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2. Flegal
KM, Kruszon-Moran D, Carroll MD, Fryar CD, Ogden CL.
Trends in obesity among adults in the United States, 2005 to 2014. JAMA.
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ArticlePubMedGoogle ScholarCrossref
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3. National
Center for Health Statistics. National Health and Nutrition
Examination Survey: questionnaires, datasets, and related documentation. https://www.cdc.gov/nchs/nhanes/nhanes_questionnaires.htm.
Accessed March 8, 2018.
4. Jensen MD,
Ryan DH, Apovian CM, et al. 2013 AHA/ACC/TOS guideline
for the management of overweight and obesity in adults. Circulation.
2014;129(25)(suppl 2):S102-S138.PubMedGoogle ScholarCrossref
5. National
Center for Health Statistics. National Center for Health
Statistics data presentation standards for proportions. https://www.cdc.gov/nchs/data/series/sr_02/sr02_175.pdf.
Accessed March 8, 2018.
6. Lumley
T. Survey: analysis of complex survey samples. 2017. https://cran.r-project.org/web/packages/survey/index.html.
Accessed March 8, 2018.
https://jamanetwork.com/journals/jama/fullarticle/2676543?mod=djem_b_reviewpreview_20180326
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