Obese adolescents are 16 times more likely to become severely obese by age 30 than their healthy-weight or even overweight peers, according to researchers at the University of North Carolina at Chapel Hill.

In a study published in the Nov. 10 issue of the Journal of the American Medical Association, researchers at the UNC Gillings School of Global Public Health found that nearly 40 percent of obese adolescents were expected to become severely obese, compared to only 2.5 percent of their healthy-weight or overweight peers.

Researchers defined adult severe obesity as a body mass index (BMI) of greater than or equal to 40, and being overweight and obese as a BMI greater than 25.

"This study highlights the importance for interventions both targeted at obesity before adolescence and also preventing the transition from obesity in adolescents to severe obesity,” Natalie The, a postdoctoral research associate and lead author of the study, said.

The 13-year study involved more than 8,000 individuals, ages 12 to 21, across all weight, sex and racial and ethnic groups. Nearly 8 percent who were not severely obese as teens became severely obese as young adults. Seventy percent of the teens who were severely obese remained so as they aged.

The study found that while 1.2 percent of males and 2.4 percent of females who were normal weight as adolescents became severely obese as adults, 37 percent of males and 51 percent of females who were obese as adolescents became severely obese as adults. The risk of becoming severely obese was highest in black females.

The link found between adolescent obesity and adult severe obesity suggests intervention programs might be most effective during childhood or adolescence, before the worst weight gain occurs, said senior study author Penny Gordon-Larsen, Ph.D., an associate professor of nutrition at UNC.

"Obese adolescents are at considerably high risk for becoming adults with severe obesity," Gordon-Larsen said. "Given the rapid rise in severe obesity and its associated health risks, early prevention efforts are critically needed."