Study Shows CDC May Have Underestimated Prevalence of Obesity in U.S.

The Centers for Disease Control and Prevention (CDC) may have underestimated the number of obese adults in the U.S. in its 2013 Obesity Prevalence Maps by at least 12 million because of reliance upon self-reported height and weight figures, according to a new study by researchers at Columbia University's Mailman School of Public Health, Harvard T.H. Chan School of Public Health, and colleagues. The researchers upped the estimated number of obese adults in 2013 from about 69 million to 81 million of 240 million adults. Approximately 33 million of the 81 million were considered to have severe obesity, defined as a body mass index (BMI) of 35 or above. Findings from the paper, “Redrawing the U.S. Obesity Landscape: Bias-Corrected Estimates of State-Specific Adult Obesity Prevalence,” are published in PLOS ONE.

The study is part of the CHOICES Project, a research program to identify and prioritize cost-effective strategies to prevent childhood obesity. The CDC maps are updated annually and along with related data help drive state obesity prevention efforts and the allocation of federal obesity prevention resources. The CDC data were gathered by telephone as part of the Behavioral Risk Factor Surveillance System. 

The authors used new statistical methods to provide adult obesity estimates that corrected those indicated in the CDC’s 2013 maps; in many states the rates were higher than previously reported. According to the researchers, the corrected state-level estimates provide decision makers with a more solid foundation of data on which to base obesity prevention policies.

Among the key findings:
•    Four states (California, Colorado, Hawaii, and Massachusetts) showed adult obesity prevalence below 30%. This contrasts with the CDC data, which suggested that a majority of states were below this level.
•    Four states (Arkansas, Mississippi, Tennessee, and West Virginia) had an estimated obesity prevalence of over 40%, a category not included in any previous CDC data. Three of these states (Alabama, Mississippi, and West Virginia) had a prevalence of severe obesity greater than 17.5%, a level also not previously seen in CDC data.
•    Undercounting the population with obesity by 12 million results in underestimating state obesity-related healthcare costs by at least $12 billion.