Questions for Craig Hales, Health Statistician and Lead Author of “Prevalence of Obesity and Severe Obesity Among Adults: United States, 2017–2018.”
Q: How has the prevalence of obesity and severe obesity in U.S. adults changed since 1999-2000?
CH: The prevalence of obesity and severe obesity among U.S. adults increased since 1999-2000. The prevalence of obesity was 30.5% among adults in 1999-2000 and increased more than 10 percentage points to 42.4% in 2017-2018. The prevalence of severe obesity among adults almost doubled from 4.7% in 1999-2000 to 9.2% in 2017-2018. The prevalence for obesity and severe obesity in 2017-2018 is the highest ever reported among all U.S. adults.
Q: Can you explain the differences between obesity and severe obesity?
CH: The definitions of obesity and severe obesity are based on the body mass index, or BMI, which is based on your weight and your height. Obesity is defined as having a BMI of 30 or higher, and severe obesity is defined as having a BMI of 40 or higher.
Q: How far back do you have obesity trend data?
CH: The trends reported in this data brief go back to 1999-2000, which is when NHANES began running as a continuous survey. However, NHANES began collecting height and weight data among adults aged 20-74 in 1960-1962. At that time, obesity prevalence was 13.4% and severe obesity prevalence was 0.9%.
Q: Was there a specific finding in the data that surprised you?
CH: What I found most striking is that more than 40% of adults in the US had obesity in 2017-2018, which is more than 10 percentage points higher than the prevalence was in 1999-2000. The prevalence of severe obesity among adults has almost doubled from 4.7% in 1999-2000 to 9.2% in 2017-2018. The prevalence of obesity and severe obesity in 2017-2018 is the highest ever reported among all U.S. adults.
Q: When will you have 2017-2018 children’s obesity data available?
CH: NHANES height and weight data for children and adolescents are currently available on the NHANES website. Estimates for obesity and severe obesity among children and adolescents will be published in the near future.
Q: Anything else you’d like to note about the new report?
CH: Measured height and weight is the gold standard for generating accurate estimates of obesity prevalence. The National Health and Nutrition Examination Survey is unique in that it combines both interviews in the home and physical examinations in mobile examination centers, and it is the only national survey where people’s height and weight are physically measured.
Other surveys report obesity prevalence based on self-reported height and weight, but several studies have found serious inaccuracies with self-reported or proxy-reported height and weight. Among adults, self-reported height tends to be overreported and weight is underreported, although misreporting can vary among subgroups of the population – but this misreporting leads to underestimates of obesity prevalence.