Prevalence of Obesity and Severe Obesity in US Children, 1999–2016

Discussion

Despite reports that obesity in children and adolescents in the United States has stabilized in recent years,¹ our more nuanced view highlights the continued upward trend for this nationally representative sample (Fig 1). Significant increases in obesity and severe obesity in children aged 2 to 5 years and adolescent females aged 16 to 19 years from 2015 to 2016, compared with previous years, show that obesity is increasing in these subgroups. Whether this year-over-year change represents a trend remains to be seen because shifts per cycle can be large. We recommend that readers consider both the long-term trends as well as changes over 2-year cycles when considering the effects in specific populations.

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FIGURE 1

The prevalence of obesity and severe obesity among US children 2 to 19 years of age from 1999 to 2016.

The prevalence of childhood obesity in the United States remains high, with ∼1 in 5 children having obesity. By applying updated obesity classifications¹⁶ to data starting in the 1999–2000 cycle of the NHANES, there continue to be increases in most categories of obesity across all age groups. By age, adolescents have had a significantly increased prevalence across all obesity categories since the 1999–2000 cycle. Substantial racial-ethnic differences remain, with African Americans and Hispanics having a higher prevalence across nearly all classes of obesity and all years between 1999 and 2016. Notably, Asian Americans have a much lower prevalence of obesity in all age and sex categories. There were few differences in obesity prevalence from the previous cycle (2013–2014), with the exception of Hispanic males, who saw significant increases, and boys ages 2 to 5 years, who have had a 40% increase in prevalence since 2011.

Despite intense clinical and public health focus on obesity and weight-related behaviors during the past decade, obesity prevalence remains high, with scant evidence that these efforts are counteracting the personal and environmental forces that contribute to excess weight gain in children, at least on a national scope. These findings are disappointing in light of reported decreases in obesity prevalence in younger children,^2,4,17–21 which was the only age group as a whole to see a significant increase in prevalence since the 2013–2014 NHANES cycle. Most disconcerting are the substantial disparities in obesity by race and ethnicity; statistical and clinical differences in prevalence between Hispanics and all other races are astounding, with nearly half of all Hispanic youth having overweight or obesity. Building on our previous work,^5,6,12 we have been able to document the steadily rising levels of severe obesity, modeled on adult criteria of class I, II, and III obesity, with the rise of children with severe obesity having been the most significant.

Public health efforts to address obesity in children have been extensive, from Michelle Obama’s Let's Move campaign to the American Academy of Pediatrics establishing a Section on Obesity in 2013 that is distinct from other groups in the academy as well as countless efforts led by states, hospitals, and communities. Despite these efforts, which may have had greater impact in defined populations, more resources are clearly necessary. The obesity epidemic is becoming endemic, and this decline in Americans’ health is occurring without impactful policy at the national level. Evidence-based efforts focused on policy, family-based change, and health improvement (versus weight loss alone) may take another decade to see positive results; effective prevention and treatment interventions remain undeveloped or have not been effectively disseminated, and more insight is needed into the moderators and mediators of excessive weight gain. Additionally, evidence that behaviors in high-risk groups start at a young age suggests that efforts need to focus early in children’s lives.²²

There are few long-term studies of obesity development or treatment outcomes because this work is occurring in a Biggest Loser environment, with the focus being on short-term changes in weight that we are only beginning to see as an erroneous pursuit in adult populations.²³ These efforts are hampered by declining research dollars, limited or nonexistent reimbursement for prevention and treatment, and difficulties in changing local and national policies that impact environmental health. Finally, there is some evidence of an association between poverty and obesity,²⁴ undoubtedly influencing the health of children nationwide. Activities with the aim of decreasing the prevalence of childhood obesity should not cease but redouble as an effort to improve the health of children and families and stem the rising costs of health care in the United States.

There are several important limitations to note. First, the NHANES data are repeated cross-sections and do not allow for the examination of within-child changes over time. However, this approach allows for a richer picture of obesity prevalence across the United States. A second limitation is that the sample sizes prevent detailed subgroup analyses. We present prevalence rates by age, sex, and race, but caution should be used when interpreting these results. Readers should consider the body of evidence rather than focusing on individual tests of significance. Finally, the inclusion of Asian Americans in this report highlights questions about the reference ranges that define obesity. The current reference charts were developed by using data from a more homogenous group than what is seen in the United States today. It is not clear if the definitions of obesity represent similar levels of adiposity across racial and ethnic groups or if they confer similar levels of health risk.