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Obesity Prevalence Among U.S. Adults During the COVID-19 Pandemic

  • Brandon J. Restrepo
    Correspondence
    Address correspondence to: Brandon J. Restrepo, PhD, Diet, Safety and Health Economics Branch, Food Economics Division, Economic Research Service, U.S. Department of Agriculture, 355 E Street, Southwest, Washington DC 20024.
    Affiliations
    Diet, Safety and Health Economics Branch, Food Economics Division, Economic Research Service, U.S. Department of Agriculture, Washington, District of Columbia
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      Introduction

      As the COVID-19 pandemic unfolded, several studies collected small and relatively homogenous samples to track U.S. adult obesity rates and obesity-related risk factors. In this study, a much larger sample from a nationally representative survey was used to investigate changes in average BMI, obesity prevalence rates, and 4 obesity-related risk factors in the U.S. adult population during the COVID-19 pandemic.

      Methods

      Using a large nationally representative sample of U.S. adults aged ≥20 years from the 2011–2020 Behavioral Risk Factor Surveillance System, linear regression models estimated intra-pandemic changes in average BMI and obesity prevalence rates as well as 4 obesity-related risk factors.

      Results

      Relative to the 2019 to prepandemic 2020 period, significantly higher average BMI (+0.6%, p<0.05, N=3,555,865) and obesity prevalence rates (+3%, p<0.05, N=3,555,865) were observed among U.S. adults during the COVID-19 pandemic. Significantly higher rates of any exercise participation (+4.4%, p<0.01, N=3,607,272), average sleep hours in a 24-hour period (+1.5%, p<0.01, N=1,907,798), average alcoholic drink days in the past month (+2.7%, p<0.05, N=3,577,090), and lower rates of smoking at least some days (−4%, p<0.01, N=3,625,180) were also observed.

      Conclusions

      During the COVID-19 pandemic, U.S. adult obesity rates were higher and worsened the pre-existing epidemic of adult obesity in the U.S. Higher rates of alcohol consumption and lower smoking rates may have contributed to the higher rates of adult obesity in the U.S during the COVID-19 pandemic.

      INTRODUCTION

      In 2017–2018, obesity prevalence among U.S. adults was estimated to be 42.4%.
      • Hales CM
      • Carroll MD
      • Fryar CD
      • Ogden CL
      Prevalence of obesity and severe obesity among adults: United States, 2017-2018.
      As the coronavirus disease 2019 (COVID-19) pandemic unfolded, weight gain in the adult population was reported by several studies, suggesting that intra-pandemic behavior changes caused a positive energy balance that exacerbated the adult obesity epidemic. An online survey conducted in April 2020–May 2020 indicated that weight gain was reported by almost 1 in 3 participants overall and by more than one-third of participants who had obesity.
      • Flanagan EW
      • Beyl RA
      • Fearnbach SN
      • Altazan AD
      • Martin CK
      • Redman LM
      The impact of COVID-19 stay-at-home orders on health behaviors in adults.
      In February 2020–June 2020, analysis of repeated weight measures from adult participants of the Health eHeart Study revealed an average gain of 1.5 pounds per month after local and state shelter-in-place orders were implemented.
      • Lin AL
      • Vittinghoff E
      • Olgin JE
      • Pletcher MJ
      • Marcus GM.
      Body weight changes during pandemic-related shelter-in-place in a longitudinal cohort study.
      Similarly, in an online survey of adults during May 2020–August 2020, the average weight gain reported across all participants amounted to 1.3 pounds, with 1 in 4 participants who had obesity reporting an average weight gain >3 times higher (4.4 pounds).
      • Seal A
      • Schaffner A
      • Phelan S
      • et al.
      COVID-19 pandemic and stay-at-home mandates promote weight gain in US adults.
      Given the rapidity with which adults gained weight, it is likely that intra-pandemic changes in risky dietary or other health-related behaviors contributed to the rise in body weight during the pandemic. Indeed, studies using online survey data found that adult participants who reported that they gained weight during the pandemic also reported more frequent snacking and alcohol intake
      • Bhutani S
      • vanDellen MR
      • Cooper JA
      Longitudinal weight gain and related risk behaviors during the COVID-19 pandemic in adults in the U.S.
      ; increased eating in response to sight, smell, and stress
      • Zachary Z
      • Brianna F
      • Brianna L
      • et al.
      Self-quarantine and weight gain related risk factors during the COVID-19 pandemic.
      ; and decreased physical activity.
      • Flanagan EW
      • Beyl RA
      • Fearnbach SN
      • Altazan AD
      • Martin CK
      • Redman LM
      The impact of COVID-19 stay-at-home orders on health behaviors in adults.
      Though prior studies provide insights into how obesity prevalence changed during the pandemic, it is unclear whether results from nonrepresentative samples generalize to the broader adult population. This study contributes to the literature by using nationally representative data on adults aged ≥20 years from the 2011–2020 Behavioral Risk Factor Surveillance System (BRFSS) to analyze changes in average BMI and obesity prevalence rates during the pandemic. Several behaviors that can influence obesity risk—exercise, sleep duration, alcohol use, and smoking—are also examined to help explain observed changes in average BMI and obesity prevalence rates.

      METHODS

      The BRFSS collects data about U.S. residents from all 50 states, the District of Columbia, and 3 U.S. territories regarding health-related risk behaviors and chronic health conditions. This study used only public-use deidentified BRFSS data. To estimate intra-pandemic changes in average BMI, obesity prevalence rates, and 4 obesity-related risk measures—participation in any physical activity in the past month, average sleep hours in a 24-hour period, number of days in the past month when any amount of alcohol was consumed, and cigarette smoking every day or on some days—among adults aged ≥20 years in the 2011–2020 BRFSS, the following linear regression model was estimated by ordinary least squares:
      Yit=α+Xitβ+γjj=20112018InterviewYearit+δCOVIDPandemicit+εit,
      (1)


      where Yit is either a body weight measure or an obesity-related risk factor for individual i at time t; Xit is a vector of individual characteristics—age, sex, race/ethnicity, education, income, marital status, and number of children—that account for changing demographic characteristics over time that could affect body weight or obesity risk as well as the survey respondent's location; ∑ Interview Year represents 8 indicator variables equal to 1 if the survey respondent was interviewed in a prepandemic year 2011, 2012, …, 2018 and 0 otherwise; COVID Pandemic is an indicator variable equal to 1 if the survey respondent was interviewed after the President of the U.S. declared the spread of the novel coronavirus a pandemic (March 13, 2020) and 0 otherwise; and εit is a random error term. All interview period coefficient estimates are estimated relative to the (omitted) 2019 to March 12, 2020 period.
      The primary dependent variable of interest, BMI, is derived from self-reported height and weight. As these measures are often misreported, they were adjusted for measurement error using a percentile-based approach with data from the 2011 to March 2020 National Health and Nutrition Examination Survey.
      • Courtemanche C
      • Pinkston JC
      • Stewart J.
      Adjusting body mass for measurement error with invalid validation data.
      The adjusted height and weight data were used to compute an adjusted BMI measure and an adjusted obesity indicator (BMI ≥30). Table 1 contains the summary statistics for the dependent and independent variables used in the analysis. For BMI/obesity, the analysis involved 3,555,865 respondents (3,311,457 before the pandemic and 244,408 during the pandemic). Consistent with BRFSS respondents overestimating height and underestimating weight, adjusted BMI and obesity are higher than unadjusted BMI and obesity (Table 1).
      Table 1Summary Statistics for the Overall Sample, 2011‒2020 Behavioral Risk Factor Surveillance System
      VariablesMean or %SD
      BMI (unadjusted)28.1396.315
      Obese (unadjusted)30.8%
      BMI (adjusted)29.0516.620
      Obese (adjusted)36.7%
      Any physical activity in past month
      The overall N=3,607,272. The prepandemic n=3,349,482 and intra-pandemic n=257,790.
      75.6%
      Average hours of sleep in a 24-hour period
      The overall N=1,907,798. The prepandemic n=1,652,408 and intra-pandemic n=255,390.
      6.9581.469
      Number of days in the past month alcohol was consumed
      The overall N=3,577,090. The prepandemic n=3,328,705 and intra-pandemic n=248,385.
      5.0798.071
      Currently, smoking some days or every day
      The overall N=3,625,180. The prepandemic n=3,374,039 and intra-pandemic n=251,141.
      17.6%
      Age in years48.09316.914
      Sex
       Female49.5%
       Male50.5%
      Racial/ethnic group
       Non-Hispanic White65.4%
       Non-Hispanic Black11.7%
       Hispanic15.3%
       Other7.7%
      Educational attainment
       Never attended school or only kindergarten0.2%
       Grades 1 through 8 (elementary)3.8%
       Grades 9 to 11 (some high school)8.2%
       Grade 12 or GED (high school graduate)26.8%
       College 1 year to 3 years (some college)31.5%
       College 4 years or more (college graduate)29.5%
      Household income, $
       <10,0005.8%
       10,000 to <15,0005.3%
       15,000 to <20,0007.5%
       20,000 to <25,0009.1%
       25,000 to <35,00010.5%
       35,000 to <50,00013.6%
       50,000 to <75,00015.3%
       >75,00033.0%
      Marital status
       Married or a member of an unmarried couple58.1%
       Divorced11.6%
       Widowed6.6%
       Separated2.6%
       Never married21.1%
      Number of children under 18 years of age in the household
       063.0%
       114.9%
       213.4%
       35.8%
       42.0%
       ≥51.0%
      Time period
       Year 20119.9%
       Year 201210.2%
       Year 201310.1%
       Year 201410.0%
       Year 20159.7%
       Year 201610.1%
       Year 201710.2%
       Year 20189.8%
       Year 2019–March 12, 202011.7%
       March 13, 2020–March 18, 20218.2%
      Note: These are summary statistics corresponding to the regression sample involving BMI/obesity as a dependent variable: the overall N=3,555,865, the prepandemic n=3,311,457, and intra-pandemic n=244,408. To produce nationally representative estimates, the appropriate BRFSS sampling weights, strata, and primary sampling units were applied in computing these summary statistics. Because of missing information on the other dependent variables used in the regression analyses summarized in Figure 1, the sample sizes are smaller and are as follows:
      a The overall N=3,607,272. The prepandemic n=3,349,482 and intra-pandemic n=257,790.
      b The overall N=1,907,798. The prepandemic n=1,652,408 and intra-pandemic n=255,390.
      c The overall N=3,577,090. The prepandemic n=3,328,705 and intra-pandemic n=248,385.
      d The overall N=3,625,180. The prepandemic n=3,374,039 and intra-pandemic n=251,141.
      There was significant skewness in the continuous dependent variables (BMI, sleep hours, and alcoholic drink days); therefore, they were log-transformed in the regression analysis. The primary independent variable of interest (COVID Pandemic) is a binary variable, so in linear regressions involving logged continuous dependent variables, percentage changes relative to the 2019 to March 12, 2020 period were obtained by applying the formula 100 × exp (linear coefficient estimate)−100. In linear regressions involving binary dependent variables, coefficient estimates were divided by sample means to obtain percentage changes relative to the 2019 to March 12, 2020 period.
      All analyses were conducted using Stata, version 17. To account for the complex survey design of the BRFSS and produce nationally representative estimates, BRFSS sampling weights, strata, and primary sampling units were applied using Stata's estimation commands for survey data.

      RESULTS

      Figure 1 shows the linear regression coefficient estimates associated with the indicator for the COVID-19 pandemic period. The analysis reveals that, relative to the 2019 to March 12, 2020 period, average BMI was higher by 0.6% (p<0.05) and obesity prevalence rates were higher by 1.1 percentage points or 3% relative to the sample mean (p<0.05). Exercise participation rates were higher by 3.3 percentage points (or 4.4%) (p<0.01), average sleep hours were higher by 1.5% (p<0.01), average alcoholic drink days were higher by 2.7% (p<0.05), and smoking rates were lower by 0.7 percentage points (or 4%) (p<0.01).
      Figure 1
      Figure 1Changes in average BMI, obesity prevalence rates, and obesity-related risk factors during the COVID-19 pandemic.
      Source: 2011‒2020 Behavioral Risk Factor Surveillance System.
      Note: Each marker shows the linear regression coefficient estimate—relative to the 2019 to March 12, 2020, period—associated with an indicator for the COVID-19 pandemic period from a separate linear regression model estimated by Ordinary Least Squares along with the corresponding 95% confidence band. To compute nationally representative estimates, the appropriate BRFSS sampling weights, strata, and primary sampling units were used in all regressions. Each coefficient estimate shown is statistically significant at the 5% level or better. Please see the notes in for the sample sizes for the 6 separate regression models. For the continuous dependent variables, to obtain percentage changes, the formula 100 × exp (linear regression coefficient estimate) − 100 must be applied. To obtain percentage changes for the binary dependent variables, the linear regression coefficient estimate must be divided by the sample mean. Regressors included but not shown: age and its square, male dummy, race/ethnicity dummies, educational attainment dummies, annual household income dummies, marital status dummies, number of children under 18 years of age in the household dummies, indicators for survey years 2011, 2012, …, 2018, and indicators for the survey respondent's state of residence.

      DISCUSSION

      Relative to the 2019 to March 12, 2020 period, significantly higher average BMI and obesity prevalence rates during the COVID-19 pandemic were observed among adults. Significant changes in several obesity-related risk indicators were also observed. Higher rates of alcohol consumption and lower smoking rates may have contributed to higher obesity prevalence rates. Indeed, higher alcohol intake has been shown to be a risk factor for obesity in some adults, particularly when it is not compensated for through reductions in intake of other calorie-dense foods and beverages.
      • Traversy G
      • Chaput JP.
      Alcohol consumption and obesity: an update.
      Quitting smoking has also been shown to lead to weight gain, both in the short and longer term.
      • Courtemanche C
      • Tchernis R
      • Ukert B.
      The effect of smoking on obesity: evidence from a randomized trial.
      Higher exercise participation and average sleep duration can reduce obesity risk.
      • Omer T.
      The causes of obesity: an in-depth review.
      However, given the observed higher obesity prevalence rates, higher exercise participation rates and average hours of sleep were not enough to offset behavior changes that increased obesity risk. Given that >40% of adults currently have obesity, which raises annual medical costs by approximately $3,632 (2020 dollars),
      • Cawley J
      • Meyerhoefer C.
      The medical care costs of obesity: an instrumental variables approach.
      continued surveillance of obesity prevalence rates and obesity-related risk factors can help to inform policy that is designed to mitigate the health and economic burdens of obesity.
      • Tremmel M
      • Gerdtham UG
      • Nilsson PM
      • Saha S.
      Economic burden of obesity: a systematic literature review.
      A major strength of this study is its ability to estimate intra-pandemic obesity prevalence rates and obesity-related risk factors using a large nationally representative survey. The BRFSS is, however, a cross-sectional data set. Future work exploiting longitudinal data to explore the dynamics of weight status among the same individuals during the pandemic would be useful. Another important limitation is that BRFSS respondents were not asked whether they had COVID-19, which may have affected obesity-related risk factors. Moreover, obesity is a complex disease, and there are many risky behaviors that could have contributed to the higher obesity prevalence rates documented here, including changes in dietary intake that are unmeasured in the BRFSS data. An important direction for future research is to examine whether adults shifted toward more calorie-dense eating patterns during the pandemic. These results may prove to be useful inputs in policymaking decisions regarding potential actions to combat the exacerbated adult obesity epidemic as the COVID-19 pandemic subsides.

      ACKNOWLEDGMENTS

      The findings and conclusions in this study are those of the author and should not be construed to represent any official U.S. Department of Agriculture or U.S. Government determination or policy.
      This research was supported by the Economic Research Service, U.S. Department of Agriculture.
      No financial disclosures were reported by the authors of this paper.

      CRediT AUTHOR STATEMENT

      Brandon J. Restrepo: Conceptualization; Data Curation; Formal Analysis; Investigation; Methodology; Validation; Visualization; Writing - Original Draft; Writing - Review and Editing.

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