Adolescents were watching less TV, eating fewer sweets, and drinking fewer sweetened soft drinks in 2010 than they were in 2001, yet their body mass index percentiles went up, not down, according to a recent study. The study also found U.S. teens were eating more fruits and vegetables, having breakfast more often, and getting more physical activity in 2010 than they were in 2001.
"It may be that current public health efforts are succeeding," Ronald J. Iannotti, Ph.D., and Jing Wang, Ph.D., of the Eunice Kennedy Shriver National Institute of Child Health and Human Development reported in Pediatrics (2013 Sept. 16 [doi:10.1542/peds.2013-1488]). "Yet it appears that the magnitude of these changes in health behaviors were not sufficient to reverse the trends in weight status."
©Pressmaster/iStockphoto.com
U.S. teens were eating more fruits and vegetables, having breakfast more often, and getting more physical activity in 2010 than they were in 2001.
Dr. Iannotti and Dr. Wang analyzed results from the Health Behavior in School-Aged Children surveys administered to three nationally representative samples of U.S. high school students in grades 6 through 10. The 83% response rate in 2001-2002 yielded a sample of 14,818 adolescents; the 87% response rate in 2005-2006 yielded 9,227 participants; and the 89% response rate in 2009-2010 yielded 10,993 participants. The researchers oversampled black and Hispanic students "to obtain better estimates for these groups."
From 2001 to 2010, physical activity among adolescents overall increased even though it remained fewer than 5 days/week for all three samples. The number of days teens reported getting at least 60 minutes of physical activity increased from 4.33 days/week in 2001-2002 to 4.53 days in 2009-2010. For each sample, boys reported more physical activity than did girls, and Hispanics reported less physical activity than did whites.
As physical activity increased, there was a drop in TV watching (P less than .001), from 3.06 hours/day in 2001-2002 (weight-averaged for weekdays and weekends) to 2.65 hours daily in 2005-2006 and 2.38 hours daily in 2009-2010. Hispanics, blacks, and "other" ethnicities reported more hours of TV watching than white teens did.
Computer use and video-game playing were only assessed in 2005-2006 and 2009-2010, and neither showed any significant change overall, although an increase in video-game playing was seen among girls only. Participants averaged less than 2 hours/day of video-game playing, which was higher in boys, younger teens, and nonwhite teens. Computer use – higher in girls, older teens, and also nonwhite teens – averaged less than 2 hours/day (P less than .001 for all results).
Assessment of fruit and vegetable intake was done on a scale of 1 (never) to 7 (more than once a day), with 6 denoting a serving at least once a day. Intake for both increased over the three samples (P less than .001), with a mean 4.29 for fruits and 4.31 for vegetables in 2001-2002 increasing to 4.91 for fruits and 4.61 for vegetables in 2009-2010. The increase in vegetables was driven by boys from 2001-2002 to 2005-2006 and in girls for 2005-2006 to 2009-2010.
Meanwhile, sweets and sweetened soft drinks, measured on the same 1-7 scale, decreased over time (P less than .001) with the greatest drop for soft drinks occurring between 2001-2002 and 2005-2006. In 2001-2002, a mean 4.7 was reported for sweets and mean 4.85 was reported for sweetened soft drinks. These decreased to 4.48 for sweets and 4.36 for sweetened soft drinks in 2005-2006 and 4.1 for sweets and 4.18 for sweetened soft drinks in 2009-2010.
Another improvement seen across the samples was an increase in adolescents’ reporting eating breakfast on weekdays (P less than .001). The teens reported eating breakfast an average of 2.98 days/weekday in 2001-2002, which increased to 3.12 in 2005-2006 and 3.25 in 2009-2010. No significant change was seen in breakfasts eaten on weekends (1.59 days/weekend in 2001-2002 to 1.62 days/weekend in 2009-2010). Those less frequently eating breakfast tended to be females, older adolescents, and blacks and Hispanics (P less than .001).
Yet, despite the decrease in obesogenic behaviors and the increase in healthy behaviors, average body mass index (BMI) percentiles in the teens increased over time, driven by the increase from 2001-2002 to 2005-2006 among both boys and girls. While 70.1% of the sample had a normal weight in 2001-2002, this dropped to 66.6% in 2005-2006 and remained similar (66.5%) in 2009-2010. Meanwhile, the percentage of overweight (14.9%) and obese (10.3%) teens in 2001-2002 increased to 17% and 12.7%, respectively, in 2005-2006 and similarly stabilized at 16.6% and 12.7%, respectively, in 2009-2010.
In line with other research, black boys had 1.36 times greater odds and black girls had 2.19 greater odds of being obese, compared with white boys and girls. Hispanics were also more likely than whites to be obese, with an odds ratio of 1.79 for Hispanic boys and an OR of 1.60 for Hispanic girls.