Half of U.S. Adults Obese by 2030?

Severe obesity also projected to be more common, affecting nearly 25% of the population in 25 states.

This article was first published on Wednesday, December 18, 2019 in MedPage Today.

By Jeff Minerd, Contributing Writer

Ten years from now, nearly half of U.S. adults will be obese if current trends continue, researchers predict, noting that almost one-quarter will be severely obese, and the epidemic will hit some states even harder.

By 2030, 48.9% of adults nationwide will be obese, defined as having a body mass index (BMI) of 30 to 35 (95% CI 47.7%-50.1%). The prevalence of obesity will be more than 50% in 29 states, and it will not be less than 35% in any state, noted Zachary Ward, MPH, of the Harvard T.H. Chan School of Public Health in Boston, and colleagues.

Also by 2030, 24.2% of adults will be severely obese, with a BMI of 35 or greater (95% CI 22.9%-25.5%). The prevalence of severe obesity will be higher than 25% in 25 states, Ward's group said in their study online in the New England Journal of Medicine.

The estimates, based on national survey data, corrected for self-reporting bias also indicated that severe obesity is likely to become the most common BMI category among women (27.6%), non-Hispanic blacks (31.7%), and low-income adults (31.7%) by 2030.

"The high projected prevalence of severe obesity among low-income adults and the high medical costs of severe obesity have substantial implications for future health care costs, especially as states expand access to obesity-related services for adult Medicaid beneficiaries," Ward and co-authors wrote.

"Although severe obesity was once a rare condition, our findings suggest that it will soon be the most common BMI category in the patient populations of many health care providers. Given that health professionals are often poorly prepared to treat obesity, this impending burden of severe obesity and associated medical complications has implications for medical practice and education," the researchers stated.

A state-by-state analysis found that obesity prevalence will reach 58% in Alabama, Arkansas, Mississippi, and Oklahoma. States projected to have the lowest prevalence of obesity by 2030 include California (41%), Colorado (38%), and Hawaii (41%). The District of Columbia was projected to have the lowest prevalence of all, at 35%.

The predictions are likely to be accurate because they are based on data from more than six million adults who participated in the Behavioral Risk Factor Surveillance System Survey in 1993-1994 and 1999-2016, the researchers said. Although survey participants self-reported their height and weight, the team corrected for potential self-reporting bias using data from more than 57,000 adults whose height and weight were actually measured in the National Health and Nutrition Examination Survey (NHANES).

"By adjusting the entire distribution of reported BMI to be consistent with measured BMI in NHANES, we adjusted for self-reporting bias while preserving the relative position of each person's BMI," the researchers explained. "Specifically, we estimated the difference between participant-reported BMI and measured BMI according to quantile and then fit cubic splines to smoothly estimate self-reporting bias across the entire BMI distribution. Each person's BMI was then adjusted for this bias given his or her BMI quantile."

June Stevens, PhD, of the University of North Carolina at Chapel Hill and a spokesperson for The Obesity Society, said the potential public health implications of the study "are, in a word, devastating. The projection that nearly one in four adults will have severe obesity in 2030 is particularly distressing," she wrote in an email to MedPage Today. "Severe obesity is associated with much more disability, disease, and death than moderate obesity. The high rates of severe obesity will impact our country's medical costs and productivity, and potentially our national defense."

Stevens, who was not involved in the study, said that while the projections are glum, they are based on the assumption that increases in obesity prevalence will continue at the same rates as they have in past years. That assumption need not hold, however, she said. With work, the trend can be changed.

"Obesity is a difficult disease to prevent and treat, and there is no magic bullet," she said. "It is understandable that some members of the public are frustrated with the current therapies, but they indeed do work if implemented. There is a lot we as a nation could do to better apply current approaches, and to discover new approaches. We need to do both. Prevention and treatment of obesity should be a national and personal priority."

Ward's group acknowledged that the assumption that current trends will continue is a chief limitation of the work. "Although our predictive validity checks from 2010 through 2016 help build confidence in our approach, projections through 2030 involve a much longer period, so the uncertainty around our projections may be larger than estimated," they said.