Topic: Methods & Modeling

This study examines severe obesity prevalence among US adults by sociodemographic characteristics and by state after adjusting for self-report bias. 

Zhao L, Park S, Ward ZJ, Cradock AL, Gortmaker SL, Blanck HM. State-Specific Prevalence of Severe Obesity Among Adults in the US Using Bias Correction of Self-Reported Body Mass Index. Prev Chronic Dis. 2023 Jul;20. doi:10.5888/pcd20.230005

Abstract

Introduction

Adults with severe obesity are at increased risk for poor metabolic health and may need more intensive clinical and community supports. The prevalence of severe obesity is underestimated from self-reported weight and height data. We examined severe obesity prevalence among US adults by sociodemographic characteristics and by state after adjusting for self-report bias.

Methods

Using a validated bias-correction method, we adjusted self-reported body mass index (BMI) data from the 2020 Behavioral Risk Factor Surveillance System (BRFSS) by using measured data from the National Health and Nutrition Examination Survey. We compared bias-corrected prevalence of severe obesity (BMI ≥40) with self-reported estimates by sociodemographic characteristics and state.

Results

Self-reported BRFSS data significantly underestimated the prevalence of severe obesity compared with bias-corrected estimates. In 2020, 8.8% of adults had severe obesity based on the bias-corrected estimates, whereas 5.3% of adults had severe obesity based on self-reported data. Women had a significantly higher prevalence of bias-corrected severe obesity (11.1%) than men (6.5%). State-level prevalence of bias-corrected severe obesity ranged from 5.5% (Massachusetts) to 13.2% (West Virginia). Based on bias-corrected estimates, 16 states had a prevalence of severe obesity greater than 10%, a level not seen in the self-reported estimates.

Conclusion

Self-reported BRFSS data underestimated the overall prevalence of severe obesity by 40% (5.3% vs 8.8%). Accurate state-level estimates of severe obesity can help public health and health care decision makers prioritize and plan to implement effective prevention and treatment strategies for people who are at high risk for poor metabolic health.

Funding

The work of Drs Ward, Cradock, and Gortmaker was supported in part by grants from The JPB Foundation, the National Institutes of Health (R01HL146625), and CDC (U48DP006376). The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of CDC or other funders. No copyrighted materials were used in this research.

← Back to Resources

This study aims to estimate the 10-year cost-effectiveness of school-based BMI report cards, a commonly implemented program for childhood obesity prevention in the US.

Poole MK, Gortmaker SL, Barrett JL, McCulloch SM, Rimm EB, Emmons KM, Ward ZJ, Kenney EL. The Societal Costs and Health Impacts on Obesity of BMI Report Cards in US Schools. Obesity (Silver Spring). 2023 Aug;31(8):2110-2118. doi: 10.1002/oby.23788. Epub 2023 Jul 3.

Abstract

Objective: This study aimed to estimate the 10-year cost-effectiveness of school-based BMI report cards, a commonly implemented program for childhood obesity prevention in the US where student BMI is reported to parents/guardians by letter with nutrition and physical activity resources, for students in grades 3 to 7.

Methods: A microsimulation model, using data inputs from evidence reviews on health impacts and costs, estimated: how many students would be reached if the 15 states currently measuring student BMI (but not reporting to parents/guardians) implemented BMI report cards from 2023 to 2032; how many cases of childhood obesity would be prevented; expected changes in childhood obesity prevalence; and costs to society.

Results: BMI report cards were projected to reach 8.3 million children with overweight or obesity (95% uncertainty interval [UI]: 7.7-8.9 million) but were not projected to prevent any cases of childhood obesity or significantly decrease childhood obesity prevalence. Ten-year costs totaled $210 million (95% UI: $30.5-$408 million) or $3.33 per child per year with overweight or obesity (95% UI: $3.11-$3.68).

Conclusions: School-based BMI report cards are not cost-effective childhood obesity interventions. Deimplementation should be considered to free up resources for implementing effective programs.

Funding

A CHOICES study estimates excess mortality associated with elevated body weight nationally and by US state and subgroup.

Ward ZJ, Willett WC, Hu FB, Pacheco LS, Long MW, Gortmaker SL. Excess mortality associated with elevated body weight in the USA by state and demographic subgroup: A modelling study. eClinicalMedicine. 2022 Apr;48. doi:10.1016/j.eclinm.2022.101429

The obesity epidemic in the U.S. continues to grow. Excess weight-related mortality has been estimated for the general population, however, less is known about how it varies by state and demographic subgroup within the U.S. Estimating the health consequences of obesity can improve understanding of the implications of the obesity epidemic, as excess weight is associated with increased incidence and mortality of many health conditions.

Although no comprehensive data on this topic exist in any one study or dataset, mathematical modelling is an approach that can analyze information from multiple sources and make estimates for relevant outcomes of interest. This study estimated state-level trends in excess deaths and life expectancy loss due to excess weight between 1999 and 2016 by population subgroup using a microsimulation model.

The researchers developed a computational approach to stimulate a nationally representative virtual population of U.S. adults, estimating annual all-cause mortality rates for each person according to their demographic characteristics, body mass index (BMI), and smoking history.

Using this microsimulation model, the team found that excess weight was responsible for more than:

• 1,300 excess deaths per day (nearly 500,000 per year)
• Loss in life expectancy of nearly 2.4 years in 2016

Relative excess mortality rates were nearly twice as high for women compared to men in 2016 and were higher for Black non-Hispanic adults. By state, overall excess weight-related life expectancy loss ranged from 1.75 years in Colorado to 3.18 years in Mississippi.

Excess weight has significant impacts on mortality in the U.S. with large disparities by state and subgroup. As the obesity epidemic continues to grow, premature mortality due to excess weight is likely to rise. This highlights the need for cost-effective interventions to promote healthy weight across the life course.

“Overall, we found that excess weight contributed to more than 1,300 excess deaths per day (nearly 500,000 per year) in the USA in 2016, increasing the total mortality rate by nearly 18% and resulting in nearly 2.4 years of life expectancy loss. On the basis of these findings, it is vital to invest in cost-effective policies and programs that can make a difference.” – Zach Ward, lead author.

Funding

The JPB Foundation, NIH, CDC

← Back to Resources

A study shows that the COVID-19 pandemic has worsened the risk factors for the development and progression of childhood obesity.

Chung A, Tully L, Czernin S, Thompson R, Mansoor A, Gortmaker S. Reducing risk of childhood obesity in the wake of covid-19. The BMJ. 2021;374:n1716. doi:10.1136/bmj.n1716

An international team of researchers has found that the swift and necessary public health response to the COVID-19 pandemic has had detrimental consequences for the prevention and management of childhood obesity. As societies build back from the pandemic, they recommend a focus on reducing childhood obesity risk factors through equitable, evidence-based, and government led action.

Priorities for action in reducing this risk and improving population health and health equity include promoting healthy school food and physical activity environments, reducing children’s exposure to unhealthy food marketing, and imposing taxes on sugar-sweetened beverages. These actions are proven to be successful, cost-effective, can improve health equity, and comprise a comprehensive approach to preventing childhood obesity.

During the pandemic, schools were closed for long periods of time and as a result, many children learned from home, which reduced opportunities for physical activity. School closures also reduced the availability of nutritious foods for children who rely on school meals.

The COVID-19 pandemic has also increased reliance on digital platforms for children’s learning and communication and in turn increased exposure to unhealthy food and beverage marketing, which can impair their dietary choices and consumption. The study team found that there is a need to restrict and regulate marketing of unhealthy food and beverages.

Many households were increasingly reliant on low-cost foods that are calorie dense and processed, due to the economic effects of the pandemic. The study team found that a tax on sugar-sweetened beverages is an effective public health intervention that can reduce consumption of sugar-sweetened beverages and can reduce obesity.

The researchers conclude that governments must focus on childhood obesity risk factors that were increased by the COVID-19 pandemic and take public health action to promote population health and health equity.

Watch a video summary of this paper

← Back to Resources

A CHOICES study shows that excess body weight is associated with higher health care costs for people across a wide range of body-mass-index (BMI) levels in the U.S.

Ward ZJ, Bleich SN, Long MW, Gortmaker SL. Association of body mass index with health care expenditures in the United States by age and sex. PLoS ONE. 2021 Mar;16(3): e0247307. doi10.1371/journal.pone.0247307.

Download this graphic as a PDF

To address gaps in the literature, the study’s research team, led by Zach Ward, examined the association of weight with health care costs across the entire body mass index (BMI) distribution by age and sex.

The researchers used data for BMI-related health care costs from the Medical Expenditure Panel Survey (MEPS) 2011-2016 for 175,726 participants and adjusted total costs to $US 2019. To correct for self-report bias (which often leads to underestimates of obesity prevalence), the team also adjusted reported BMI data from the MEPS.

The team found that higher health care costs are associated with excess body weight across a broad range of ages and BMI levels, and were especially high for people with severe obesity. In general, the researchers found that among adults, obesity is associated with over $1,800 in extra annual medical costs per person, which accounts for over $170 billion of annual spending in the U.S. This figure rises to over $200 billion if excess costs from overweight (over $600 per person) are included. It was also found that, among children, obesity is associated with over $100 in extra annual medical costs per person, and over $1 billion of excess medical costs in the U.S.

These findings highlight the large economic impact of overweight and obesity in the U.S. and the importance of promoting healthy weight across all BMI levels. These data will provide policymakers and health care providers with better estimates of the health care cost impacts of excess weight.

“Although extra annual medical costs associated with children with obesity are a relatively small contributor to overall excess medical spending (less than 1% of all obesity-related medical expenditures), promoting healthy child weight may help to avert future health care costs, since excess body weight during childhood is a strong predictor of excess weight during adulthood.” – lead author, Zach Ward

← Back to Resources