Introduction

The increasing prevalence of childhood obesity in the United States (U.S.) has become a significant public health concern, elevating the risk of developing cardiometabolic comorbidities among U.S. adolescents [1–4]. Recent data from the Centers for Disease Control and Prevention (CDC) [5] showed that the prevalence of obesity among children and adolescents aged 2–19 years increased from 12 million (16.9%) in 2010 to 14.7 million (19.7%) in 2020. These concerning trends have long-term implications for the health and well-being of adolescents as they transition into adulthood [6–8]. The economic burden of obesity in the U.S. healthcare system was estimated to be $173 billion in 2021 [9]. Thus, monitoring national trends and examining the association between sociodemographic factors and weight-related outcomes among adolescents are critical to increase awareness and prevent childhood obesity.

Obesity among adolescents (aged 10–19 years) is defined as age- and sex-specific body mass index (BMI) greater than or equal to the 95th percentile based on the 2000 CDC growth chart [4]. Sociodemographic factors, such as age, sex, race/ethnicity, and socioeconomic status, have been associated with the prevalence of childhood obesity [1,10–12]. For example, a recent study showed a 4.5% increase in obesity prevalence among adolescents aged 12–19, from 17.7% in 2009–2010 to 21.5% in 2017–2020 [13]. Research showed a higher prevalence of obesity in boys than girls [14].

This increased rate is particularly pronounced among certain racial and ethnic minorities [15,16]. The most recent 2020 CDC data indicated that the prevalence of obesity among Black and Hispanic children was 24.8% and 26.2%, respectively, compared to 16.6% among White children [5]. In addition, youth from lower socioeconomic backgrounds are more likely to be obese than those from higher socioeconomic backgrounds [15,17], and families with lower incomes were 1.39 times more likely to have children who are obese than those from families with higher incomes [18].

Nevertheless, most studies on sociodemographic factors in relation to childhood obesity were cross-sectional reporting point prevalence estimates [19–21], with limited studies examining the key disparities in sociodemographic factors with long-term trends in mean BMI and obesity prevalence. Thus, there are a limited amount of studies on the most recent trends in obesity prevalence among U.S. adolescents aged 10–19 years. To address these gaps, we used a nationally representative sample from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2020. The aims of this study were two-fold: 1) to illustrate trends in mean BMI and obesity prevalence among U.S. adolescents, and 2) to examine how sociodemographic factors were associated with the mean BMI and obesity prevalence among this sample of U.S. adolescents. We hypothesized that there is a significant increasing trend in mean BMI and obesity prevalence among U.S. adolescents from 2007 to 2020. Additionally, we hypothesized the sociodemographic factors have a significant association with mean BMI and obesity prevalence among the sample of U.S. adolescents.

Methods

Results

Characteristics of study population

The nationally representative sample characteristics from 2007–2008 through 2017–2020, and the characteristics were presented in Table 1. The total sample comprised 9,826 adolescents with mean age of 14.29 years (SD ± 2.78), of which 49.0% were girls. The mean BMI increased from 22.85 (95% CI: 22.40–23.29) in 2007–2008 to 23.66 (95% CI: 23.15–24.03) in 2017–2020. Furthermore, the prevalence of obesity increased from 20.71% (95% CI: 17.16–24.27) in 2007–2008 to 23.99% (95% CI: 21.31–26.67) in 2017–2020. In the overall analyses, the results revealed a statistically significant increase in both BMI and obesity prevalence from 2007 to 2017 (Tables 1, S1 and S2). Fig 1 showed overall obesity prevalence weighted proportions stratified by age, sex, race/ethnicity, and PIR. Notably, Black and Hispanic adolescents showed higher obesity prevalence proportion rates than other race/ethnicity. Moreover, adolescents from low-income demonstrated the highest prevalence.

Download:

• PPT
  PowerPoint slide
• PNG
  larger image
• TIFF
  original image

Fig 1. Weighted proportions in obesity prevalence stratify by sex, age and race/ethnicity and poverty income ratio from 2007–2008 to 2017–2020.

https://doi.org/10.1371/journal.pone.0290211.g001

Download:

• PPT
  PowerPoint slide
• PNG
  larger image
• TIFF
  original image

Table 1. Descriptive table of children and adolescents aged 10–19 years old, by overall, sex, and race/ethnicity from 2007 to 2020.

https://doi.org/10.1371/journal.pone.0290211.t001

The Wald test analysis did not reveal any significant interaction between the survey cycle and both BMI and obesity prevalence concerning age groups and sex. However, a significant interaction effect between survey cycle and both BMI and obesity prevalence was observed across various race/ethnic and PIR groups (S1 and S2 Tables).

Sociodemographic stratified trends and disparities in the BMI and prevalence of obesity

For the 15–19 age group, the mean BMI level significantly increased from 24.48 (95% CI: 23.84–25.13) in 2007–2008 to 25.53 (95% CI: 24.94–26.12) in 2020 (p <0.001) (S2A Fig and S1 Table). However, the prevalence of obesity did not significantly increase from 18.7 (95% CI: 13.25–24.15) to 22.11 (95% CI: 18.29–25.94) (Fig 2A, Table 2). Additionally, there was no significant increase in BMI levels or obesity prevalence for the 10–14 age group. For girls (boys [reference]), mean BMI levels did not significantly increase from 22.11 (95% CI: 22.33–23.50) in 2007–2008 to 23.78 (95% CI: 23.23–24.33) in 2017–2020 (p ≥0.05) (S2B Fig and S1 Table). However, there is a significant increase in the prevalence of obesity for girls (boys [reference]), from 19.37 (95% CI: 15.46–23.29) in 2007–2008 to 22.35 (95% CI: 18.47–26.22) in 2017–2020 (p <0.01) (S2B Fig and S2 Table). Similar trends in mean BMI and obesity prevalence were observed in boys.

Download:

• PPT
  PowerPoint slide
• PNG
  larger image
• TIFF
  original image

Fig 2.

Trends in prevalence of obesity among US adults (aged 10–19), NHANES 2007–2020 by (a)Age, (b) Sex, (c) Race/ethnicity, and (d) Poverty Income Ratio.

https://doi.org/10.1371/journal.pone.0290211.g002

Download:

• PPT
  PowerPoint slide
• PNG
  larger image
• TIFF
  original image

Table 2. Weighted generalized linear/Poisson models for obesity among US children and adolescents aged 10–19 years old, 2007–2020.

https://doi.org/10.1371/journal.pone.0290211.t002

Among race/ethnic groups, Black adolescents had the highest increase in mean BMI from 23.90 (95% CI: 23.28–24.53) to 25.92 (95% CI: 24.28–25.56) (p<0.001) between 2007 and 2020 (S2C Fig). Hispanic adolescents also had an increase in mean BMI from 22.54 (95% CI: 22.89–24.18) to 24.07 (95% CI: 23.31–24.83) (p <0.001). Yet, there was no significant trend in the other race group. Similarly, for the obesity prevalence (Fig 2C), Black adolescents also had the highest increase, with a rise of 5.66% from 24.96 (95% CI: 22.07–33.45) to 30.62 (95% CI: 27.18–34.06) (p <0.001) in 2007–2020. In addition, Hispanic adolescents had an increase from 24.21 (95% CI: 20.78–28.67) to 29.05 (95% CI: 22.97–35.13) (p <0.001). However, there were no significant changes in BMI and obesity prevalence in the other race and ethnic adolescents.

Adolescents from low-(PIR <1.3) and middle-income families (PIR 1.3 to <3.5) had significant increases in mean BMI (S2D Fig). Specifically, the low-income group had a mean BMI of 23.57 (95% CI: 22.83–24.31), and the middle-income group had a mean BMI of 22.84 (95% CI: 22.10–23.59) in 2007–2008 to 24.82 (95% CI: 24.22–25.42), and 23.67 (95% CI: 22.96–24.38) in 2017–2020. The prevalence of obesity also increased significantly in the middle-income group, from 19.25 (95% CI: 13.37–25.12) in 2007–2008 to 25.45 (95% CI: 21.32–29.58) in 2017–2020 (Fig 2D, S2 Table). There was a significant decrease in the prevalence of obesity in the high-income group (PIR ≥3.5), from 17.31 (95% CI: 12.51–22.21) in 2007–2008 to 14.44 (95% CI: 11.50–17.38) in 2017–2020, although no significant changes in BMI were found.

Discussion

We examined trends in BMI and obesity prevalence among US adolescents using nationally representative NHANES data from 2007–2008 to 2017–2020. This study provided the most up-to-date available US nationally representative trends over the decade. Our findings indicated that adolescent obesity continued to increase in the US over the past decade. We found the increase in both mean BMI and obesity prevalence from 2007–2008 to 2017–2020 among several subgroups of adolescents, including Black and Hispanic adolescents (compared to White counterparts), and those from low and middle-income backgrounds (compared to high-income backgrounds). Additionally, our findings indicated that obesity prevalence increased significantly among both boys and girls over the past decade. In contrast, we found no significant changes in mean BMI and a significant decrease in obesity prevalence among those from high-income groups. Our analysis also revealed persistent disparities among certain racial minorities (Black and Hispanic adolescents) and those in low and middle-income groups (PIR ≤1.3 and PIR 1.35 to <3.5) who had greater odds of being obese. These findings underscore the importance of targeted interventions to address the growing obesity epidemic among US adolescents, particularly those from minority groups and lower socioeconomic status backgrounds.

The BMI increased from 22.85 kg/m² in 2007–2008 to 23.59 kg/m² in 2017–2020 among adolescents aged 10–19, while the prevalence of obesity increased by 3.3% from 20.7% to 24% over the same time period. Our findings were consistent with prior research indicating that childhood obesity remained high in the U.S., with approximately 1 in 5 children affected 12- to 19-year-olds [30]. Notably, our study provides updated data on this trend compared to 2017–2020. In addition, our study findings are consistent with a recent study that reported a 4.5% increase in obesity prevalence among adolescents aged 12–19 from 2009–2010 to 2017–2020, yet presented only unadjusted prevalence estimates [13]. Our study included a longer time span than these previous studies through a robust multivariate survey-weighted data analysis, adjusting for key sociodemographic factors and survey cycle. Our findings demonstrated disparities in race/ethnic groups and income levels leading to obesity among U.S. adolescents. Additionally, although both boys and girls have a significant prevalence of obesity, compared to girls, boys had a higher prevalence of obesity, from 22.5% in 2007–2008 to 25.7% in 2017–2020. This finding was consistent with the findings of the previous study, which demonstrated slightly higher obesity prevalence in boys [31]. Considering sex will enable us to develop more effective and tailored strategies to improve the overall well-being and outcomes of this vulnerable population.

We found that the prevalence of obesity continues to increase among certain race/ethnic groups, as well as low-income groups. Compared to White counterparts, Black and Hispanic adolescents had higher obesity rates in 2017–2020 (30.62% and 29.05%, respectively). These findings are consistent with previous studies [12,31,32], that Black and Hispanic adolescents as having the highest obesity rates among all minority groups. other races including Asian adolescents had a lower prevalence of obesity in all age and sex groups, which is also in line the with earlier research [33]. However, it is important to note that Asians have different body compositions, and Asian children with a normal BMI range, meant for White children may still be considered overweight or obese according to Asian-specific criteria [34]. In addition, we found a decreasing trend from 17.31% in 2007–2008 to 14.44% in 2017–2020 among high income groups. Conversely, low-income families (PIR <1.3) and middle-income families (PIR 1.3 to < 3.5) had significant increases in mean BMI and obesity prevalence observed for both groups. Consistent with the pervious result showing that adolescents from low-income families had a greater chance of being obese [15], our study highlights a concerning trend of rising obesity rates among adolescents from low- and middle-income groups [35]. Since adolescents from low-income families often encounter challenges, such as limited access to healthy foods and opportunities for physical activity [36], they may face obstacles in making healthier choices than those from high-income families [37,38].

Our overall analyses examining the association between sociodemographic factors and BMI and obesity revealed persistent disparities among Black and Hispanic adolescents. Black and Hispanic adolescents had 23% and 19% greater odds of being obese compared to White counterparts. Adolescents from low and middle-income groups had higher odds of obesity, while the high-income group had lower odds. These results align with previous studies [39], indicating that socioeconomic inequalities play a significant role in shaping access to neighborhood and social resources. Furthermore, a previous systematic review demonstrated that approximately 40% of studies have identified a widening socioeconomic inequality gap since 2000 [40]. A possible explanation may be that these disparities in obesity prevalence among different race/ethnic and income groups may be linked to various factors such as residing in unsafe neighborhoods that limit opportunities [41] and limited access to healthy food options [42]. Furthermore, another study indicated that adolescents from low socioeconomic neighborhoods are more exposed to poverty, crime, low social cohesion, higher levels of air pollution, lack of green spaces, and poor quality of the built environment, which can increase the likelihood of obesity [43]. Adolescence is a critical period for preventing obesity, the results of our study underscore the substantial disparities in the prevalence of obesity existing among youth. Therefore, future research should address these disparities and promote health equality.

It is crucial to recognize that BMI and obesity prevalence demonstrated inconsistent trends across age groups. BMI provides a continuous weight assessment in relation to height, offering a comprehensive perspective on weight changes, particularly in adolescent populations. Conversely, obesity is typically defined by specific BMI thresholds and is directly associated with an elevated risk of obesity-related health concerns, including type 2 diabetes, cardiovascular disease [44]. These disparities can result in distinct interpretations when scrutinizing trends within specific demographic groups.

The strengths of this study included assessment of the most up-to-date available data from NHANES to evaluate trends over the past 13 years. In addition, while the survey data were mostly self-reported and were subject to misclassification, a strength of our approach is that the weight and height data collected from NHANES were measured by professional data collectors rather than self-report, increasing the accuracy and reliability of the results by reducing personal bias [17]. Another strength is the large sample size, which provided sufficient statistical power to examine the race- and sex-specific mean BMI and prevalence of obesity, despite not accounting for Asian American adolescents. Lastly, this study employed a rigorous multivariate survey-weighted data analysis and accounted for the key sociodemographic factors and survey cycles. This methodological approach significantly enhances the depth and reliability of the findings, strengthening the validity of the study’s conclusions.

There are two limitations. First, the NHANES data are based on repeated cross-sectional surveys, which means that we cannot examine within-child changes over time or imply causality. However, this approach still provides a valuable snapshot of obesity prevalence among US adolescents over time. In addition, including Asian American adolescents in the other group in our analysis raises questions about the validity of current reference ranges for defining obesity [33].

Conclusions

Despite efforts in public health policies and increasing awareness, the prevalence of obesity among children remains high and continues to increase among Black and Hispanic adolescents. Future research should address key disparities suggested through this analysis and promote health equality. The findings of our study suggest that future obesity interventions should target specific race/ethnic minorities and low-income families to prevent obesity. This could involve developing policies and interventions addressing social determinants of health, such as improving access to healthy food options, creating safe environments for physical activity, and promoting culturally appropriate community-based initiatives that support healthy lifestyles [43].

Supporting information

Acknowledgments

The views of this study are those of the authors and do not necessarily represent the views of the NIMHD, the NIH, and the U.S. Department of Health and Human Services.