- The average body mass index (BMI) of teenagers was stable through the 1980s and began to rise in the 1990s, according to a new study of nationwide health surveys spanning four decades.
- For young adults, average body mass index (BMI) was steady through the 1990s and began rising around 2000.
- By 2000, average body mass index (BMI) of 18-year-olds increased from 22 before and during the 1980s to 24.5.
A new study that looks at weight change over decades finds that the obesity epidemic in teens and young adults has its roots in the late 1990s and early 2000s, when body weights began to rise. But not everyone was affected equally.
“Females are at greater risk than males, and black females are at greatest risk,” said study co-author Kathleen Mullan Harris, adding that young adults seem vulnerable to weight gain. “There need to be preventive messages focused on this period.”
In the study, which appears online in the Journal of Adolescent Health, researchers analyzed statistics from four nationwide health surveys conducted over more than 40 years from 1959 to 2002, focusing on whites, African-Americans and Hispanics between the ages of 12 and 26.
The weights of young people remained fairly steady over the 1960s, 1970s and 1980s. But then they began to put on pounds. In the first few decades of the surveys, for example, 18-year-olds had an average body mass index (BMI) of 22. But average BMI grew to about 24.5 by 2000.
The average weight of an 18-year-old female who is 5 feet 5 inches tall grew from 132 pounds to 147 pounds; the average weight of an 18-year-old male at 5 feet 9 inches rose from 149 pounds to 166 pounds.
Despite the increase, however, the average 18-year-old still wasn’t considered overweight or obese in 2000.
BMI is a measurement that takes both height and weight into account. For adults, BMI between 25 and 29.9 is considered overweight, and BMI of at least 30 is considered obese. For children and adolescents, BMI calculation now also takes gender and age into account.
Over time in the study, the weight of females grew at a faster rate than that of males. From 1999 to 2002, African-American females had the highest weight levels and the fastest rate of weight gain.
Teens began putting on extra weight in the 1990s, the researchers say, while young adults did in around 2000. The researchers didn’t analyze statistics from years more recent than 2002, although Harris said it appears that the weight boom is beginning to slow, at least among adults overall. However, she said, some research suggests that on average, young people are still putting on pounds.
“For young people in particular, it has do to with more of a sedentary lifestyle and an increasing portion of weekly meals that are fast food,” Harris said.“There’s more TV watching and sitting in front of the computer, as well as more video game playing.”
Jason Fletcher, an assistant professor of public health at Yale University who studies childhood obesity, said the study findings provide new information about what’s been happening to the bodies of adolescents as they transition to adults.
“Another message is that simple explanations of the obesity increase are unlikely to be true,” Fletcher said. “They fail to capture the large differences in the obesity increases by race and gender.”
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For More Information:
Reach the Health Behavior News Service, part of the Center for Advancing Health, at email@example.com or (202) 387-2829. Journal of Adolescent Health: Contact Tor Berg at (415) 502-1373 or firstname.lastname@example.org or visit www.jahonline.org. Lee HE, et al. U.S. trends in body mass in adolescence and young adulthood, 1959-2002. J Adolesc Health online, 2011.