In 10 Years, Almost Half of All Americans Will Have Obesity

Marlene Busko

December 19, 2019

"Given current trends," researchers estimate with "high accuracy" that by 2030 nearly one in two adults in the United States will have obesity.

The obesity rate will soar above 50% in 29 states, Zachary J. Ward, MPH, and colleagues predict in their study, funded by the JPB Foundation and published December 19 in the New England Journal of Medicine.

Moreover, no state will have an obesity prevalence below 35%, which is currently considered a high level of obesity, says Ward in a video issued by his institution, the Harvard T. H. Chan School of Public Health, Boston, Massachusetts.

The new research is some of the first to delve deeply into statistics by state, they say.

"What's Even More Concerning...Is the Rise in Severe Obesity"

"What's even more concerning," Ward continues in the video, "is the rise in severe obesity. We find that, nationally, about one in four adults are projected to have severe obesity," which is usually 100 lb (45.4 kg) of excess weight.

"This was surprising," he continued, "because severe obesity has typically been a rare condition, but we find that it's growing pretty rapidly in a lot of states."

The model also predicts that, nationally, severe obesity will become the most common body mass index (BMI) category for women, non-Hispanic blacks, and low-income adults (those with household income below $50,000/year).

These projections are based on telephone survey data from more than 6 million Americans, which was adjusted to account for people reporting a lower body weight.  

The research showed that "obesity is rising in every state," said Ward, and "some states are going to be at a very high level."

In turn, "obesity, and especially severe obesity, are associated with increased rates of chronic disease and medical spending, and have negative consequences for life expectancy," noted senior author Steven L. Gortmaker, PhD, also of the Harvard T. H. Chan School of Public Health, in a press release from his institution.

One of the main drivers of the research, Ward said, was to provide more information for state policymakers.

For example, previous research by the group suggests that taxes on sugar-sweetened beverages could lower consumption and help curb the rise in obesity.

"Prevention is going to be key to better managing this epidemic," he says.  

State-Level Corrected Obesity Estimates

"Although the national obesity epidemic has been well documented," the authors write, "less is known about obesity at the US state level."

In the Behavioral Risk Factor Surveillance System (BRFSS), investigators phone a nationally representative sample of more than 400,000 US adults each year and collect state-level data, Ward and colleagues write.

But this "substantially underestimates the prevalence of obesity owing to the well-documented self-reporting bias," they note.

To better estimate state-level obesity in 2030, the researchers first obtained self-reported weight and height data from 6,264,226 US adults who participated in BRFSS surveys during 1993-1994 and 1999-2016.

They grouped people into four BMI categories: underweight or normal weight (BMI < 25 kg/m2), overweight (25 to < 30 kg/m2), moderate obesity (30 to < 35 kg/m2), and severe obesity (≥ 35 kg/m2).

Then they adjusted the BMIs so that they had a similar distribution to that of the 57,131 adults who participated in the National Health and Nutrition Examination Survey (NHANES) during those years and who had actual height and weight measurements.

On average, the BMIs from the telephone survey were increased by 0.71 units in men and by 1.76 units in women.

And these adjusted BMIs from 1999 through 2010 accurately predicted the actual prevalence of obesity in 2016.

"It's Really Hard to Lose Weight": Prevention Is Key

Next, the researchers used this approach to estimate obesity in 2030.

The findings "suggest with high predictive accuracy that by 2030 nearly one in two adults will have obesity (48.9%)," Ward and colleagues report.

The results are consistent with their previous study, as reported by Medscape Medical News, which found "57% of children 2 to 19 years of age in 2016 are projected to have obesity by the age of 35 years" (N Engl J Med. 2017;377:2145-2153).

"It's really hard to lose weight" and "it's really hard to treat obesity," Ward concluded. "So prevention really has to be at the forefront of efforts to combat this growing epidemic."

N Engl J Med, 2019;381:2440-2450. Abstract

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