Researchers have pinpointed when U.S. children and teens began tipping the scales toward obesity. The epidemic began in the late 1990s, but experts still don't know the exact cause.
The study, led by researchers at the University of North Carolina at Chapel Hill, looked at the body mass index (BMI) of about 100,000 teens and young adults ages 12 to 26. The BMIs were recorded from 1959 to 2002.
The researchers found that BMIs increased markedly for adolescents beginning in the 1990s, and among young adults around 2000. This was true especially among African-American females. Overall, BMI increases started earlier and rose faster for females than for males.
A healthy BMI is 18.5 to 24.9. A BMI of 25 to 29.9 is classified as overweight; a BMI of 30 or more is considered obese.
As BMI increases, so does the risk for obesity-related illnesses, including heart disease, diabetes, some cancers, stroke, liver disease, gallbladder disease, osteoarthritis, and fertility problems.
According to the CDC, about a third of Americans are now either overweight or obese, with slightly more women than men affected.
The researchers cited a number of possible factors for the increase in BMI among teens and young adults, including a rise in time spent with computers or watching TV and a longer time spent in post-secondary education, "transitioning" to adulthood. According to lead author Hedwig Lee, Ph.D., at the Chapel Hill campus, when young people first leave home and go out on their own, they are more likely to have bad eating habits and get little exercise.
"It used to be middle-age creep," says Lona Sandon, R.D., at the University of Texas Southwestern Medical Center. "It's scary because the earlier weight gains mean earlier onset of chronic illness such as hypertension in the 20s instead of 40s."
What can be done? Sandon says that younger children need to be taught healthy eating habits and the importance of exercise. Schools should change the types of food and beverages they serve.
For adults, workplaces need to become "exercise friendly" because that's where adults spend most of their time, Sandon says. "We need to remove the barriers" that keep people from exercising and eating healthy foods.
Always talk with your health care provider to find out more information.