The positive trends may be eating into the country's obesity epidemic.
Nationwide, childhood obesity rates have tripled since the 1980s. Now, 17 percent of all kids and adolescents are considered obese.
A representative sample of more than 30,000 adolescents aged 11 to 16 were analyzed from 2001 to 2010, so researchers could take a close look at their behaviors over the backdrop of the latest obesity trends.
Recent studies suggest the childhood obesity ratemay be leveling off or even falling slightly.However, other researchers have reportedtroubling upticks in rates of "severe obesity"among U.S. children.
For the new study, published Sept. 16 inPediatrics, researchers at the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Bethesda, Md. surveyed more than 14,500 students in 2001 to 2002, another 9,200 during the 2005-2006 school year, and nearly 11,000 adolescents during 2009 and 2010.
They were asked what they ate, how much they engaged in physical activity and how much time they spent watching television, playing video games and on the Internet.
Body mass index (BMI), a measure of obesity that incorporates weight and height, increased for adolescents between 2001 and 2006, the researchers found. There was no significant change in levels by 2010, which suggests stabilizing obesity rates.
"In some ways you can interpret what we found positively by saying we're beginning to bend the curve, and hopefully we'll start seeing a downward trend in obesity," study author Dr. Ronald J. Iannotti, who serves as chair of the exercise and health sciences department at the University of Massachusetts in Boston, told the New York Times.
They also found significantly more adolescents engaged in physical activity between 2009 and 2010 than they did a decade earlier, with the lowest rates occurring between 2001 and 2005. Hispanic adolescents were less likely to exercise than white ones.
Television viewing also decreased during the study period on weekdays and weekends, but researchers found boys watched more than girls, and black and Hispanic children watched more TV than white adolescents. Video game and computer use trends did not change significantly during the study.
What did change greatly was how adolescents ate. More children ate fruit and vegetables by 2010 than they did 10 years earlier, with rates higher in girls. Decreased rates of eating sweets like candy and drinking sugary drinks were reported over the study, but the biggest declines were seen from 2001 and 2002 to 2005 and 2006, rather than in recent years. Black adolescents consumed more sweets and soft drinks than their counterparts.
Despite several of these trends going in the right direction, the researchers say there's far more to be done to improve adolescents' health, noting most did not meet recommendations for getting 60 minutes of physical activity a day or did not eat five-plus servings of fruits and veggies daily. On the other hand, many adolescents exceeded the two-hours per day of recommended screen time and still ate too many snacks and sugary drinks for the researchers liking.
"This pattern of...behaviors is not surprising given the high prevalence of cardiovascular disease risk factors among U.S. adolescents," wrote the researchers.
A July study from the American Heart Association found that over the past 13 years,children and adolescents have seen significant rises in their risk for high blood pressure. Childhood obesity is also linked to increased risk for Type 2 diabetes, which can also contribute to heart risks.
Other experts not involved in the research agreed more work remains to get teens on track for a healthy adulthood.
"We may be beginning to see the results of our comprehensive efforts at many levels -- in schools, communities, clinical care settings and beyond -- but there is still much work that needs to be done," Melissa Laska, an associate professor of community health at the University of Minnesota in Minneapolis, told USA Today.
Sharon Strohm, manager of clinical nutrition and diabetes education at Children's Hospital of Pittsburgh, told HealthDay that public health campaigns can help, but seeing a parent exhibiting healthy behavior might be the best. Adolescents aren't too old to follow their parents' examples.
"If your child sees you trying to eat right and be healthy, it does rub off on them," she said.