Adolescent obesity associated with risk of severe obesity in adulthood

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

Public health researchers found that nearly 40 percent of obese adolescents are expected to become severely obese by age 30, compared to only 2.5 percent of healthy weight and overweight teenagers.

The study was published in the Nov. 10, 2010, issue of the Journal of the American Medical Association. It is believed to be the first longitudinal study to examine the persistence and development of severe obesity over the transition from the teenage to adult years.

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., associate professor of nutrition in the UNC Gillings School of Global Public Health and a fellow of the Carolina Population Center.

"Severe obesity can lead to life-threatening complications, including diabetes, hypertension, hyperlipidemia, asthma and arthritis, as well as substantial reductions in life expectancy," she said. "It's critical that we identify who is most at risk for this condition, and when they are most vulnerable to it. Then we'll have better evidence for when and how to effectively intervene."

Current weight loss drugs are either minimally effective or come with a high risk of side effects, while people who have bariatric surgery, or "stomach stapling" operations, can suffer major potential complications, said Natalie The, Ph.D., postdoctoral research associate and lead author of the study. Therefore, preventing severe obesity may be the most effective strategy to avoid obesity-related health risks, she said.

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.

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.

"While we know that the transition from the teenage years to the adult years is one of high risk for weight gain, few studies have tracked individuals over time to understand the risk of developing severe obesity," The said.

To measure the association between obesity in adolescence and severe obesity in adulthood, researchers studied data from the U.S. National Longitudinal Study of Adolescent Health. More than 8,800 people aged 12-21 in 1996 were followed into adulthood (ages 24-33 in 2007-2009).

Results showed that across all weight, sex and racial and ethnic groups, 7.9 percent of these teenagers who were not severely obese as adolescents became severely obese as young adults 13 years later. On the other hand, 70 percent of the teens who were severely obese remained so as they aged.

On average, over the period of the study, a teenage female of 5 feet 4 inches tall weighing 130 pounds who never developed severe obesity gained about 30 pounds; however a female of the same height who did become severely obese gained about 80 pounds.

"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."