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Editors note: This article was retracted and replaced by JAMA on Feb. 21, 2023 due to adjustment errors that did not change the overall conclusion of the findings. The updated numbers are now reflected below.

Over the past 4 decades, the average body mass index (BMI) for young adults in the U.S. rose by 4.5 points, according to a new study.

Comparing 1976-1980 to 2017-2018, average BMI grew from 23.0 (95% CI 22.8-23.2) to 27.5 (95% CI 25.5-29.4) for people in their "emerging adulthood" years (ages 18 to 25; P=0.006 for trend), reported Alejandra Ellison-Barnes, MD, MPH, of Johns Hopkins University School of Medicine in Baltimore, and colleagues.

This trend was largely driven by a sharp spike in obesity prevalence, the group wrote in a research letter in .

In 1976-1980, only 5.5% of young adults had obesity (BMI of 30 or higher). However, this number more than quintupled by 2017-2018, as nearly 33% of this age group had obesity, the analysis showed. The trend was likewise paired by a jump in overweight prevalence -- increasing from 18.2% of this population during the first survey period to 24.8% by 2018.

All in all, this equated to 57.4% of all young adults having overweight or obesity during the most recent survey cycle.

Over the past 4 decades, things really seemed to shift around the turn of the century. Throughout all the survey periods, the biggest jump in average BMI occurred between the 1988-1994 and 1999-2000 cycles -- increasing nearly two full points from 24.3 to 25.9. Between these two survey periods, the proportion of young adults with obesity also jumped from 14.8% to 19.9%.

The proportion of young adults considered to have a normal weight (i.e., BMI 18.5-24.9) was nearly cut in half during the past 40 years, dropping from 70.5% in 1976-1980 to 34.0% by 2018.

The proportion of underweight young adults (BMI less than 18.5) didn't significantly change throughout the years, however, but trended upward, at 5.9% in 1976 and 8.7% in 2018.

"Given what is known about the increasing prevalence of obesity in both children and adults, we were not surprised by the general trend, however we were surprised by the magnitude of the increase in prevalence and that the mean BMI in this age group now falls in the overweight range," Ellison-Barnes told 名媛直播.

"Given that emerging adulthood is a period of exploration, change, and transitions that ultimately influences the remainder of an individual's trajectory in adulthood, this may be an ideal time to intervene in the clinical setting to prevent, manage, or reverse obesity to prevent adverse health outcomes in the future," she added.

The findings fall in line with the bigger picture, too: When the researchers looked at the entire scope of National Health and Nutrition Examination Survey (NHANES) data for all U.S. adults ages 20 and older, 42% had obesity in 2017-2018. And more specifically, 9.2% of all adults had severe obesity -- defined as a BMI of 40 or higher -- during this survey period.

Ellison-Barnes and co-authors gathered BMI data on a total of 8,015 emerging adults from the NHANES periods II (1976-1980), NHANES III (1988-1994), and continuous cycles from 1999 through 2018. Only U.S. adults between the ages of 18 and 25 during each survey period were included.

All those in the study also had to be non-pregnant, non-Hispanic Black, and non-Hispanic white. The researchers cautioned, therefore, that the findings might not be generalizable to other ethnic or racial groups. In total, about half the cohort were female and nearly 40% were Black. Additionally, about 30% of all adults included met the criteria for household poverty.

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