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"Do it, move it, make it happen. No one ever sat their way to success."


The United States continues to battle an epidemic of physical inactivity and obesity. Over the past three decades, declines in physical inactivity have mirrored the rise in obesity among children and adolescents. Longitudinal data from the National Health and Examination Surveys show that over the past 30 years the percentage of overweight and obese adolescents in the United States has increased from 5% to over 17%. Obese youth are less likely to engage in physical activity and are much more likely to report chronic health problems compared with peers of normal weight. Obese adolescents are also more likely to be obese as adults.

During adolescence, levels of spontaneous physical activity drop significantly from childhood levels. The number of US adolescents meeting recommended activity levels is low, and this figure has not changed significantly over the past 10 years (Figure 10-1). Adolescents spend much of their time engaged in sedentary activities. Most adolescents engage in at least 1 hour of technology-related behavior (television viewing, Internet surfing, gaming device) per day. In contrast, adolescents currently average a mere 12 min/d of vigorous physical activity. One-third of US high-school students are not regularly active; one-half of high school seniors are not enrolled in physical education classes, and 70% of all high school students watch at least 1 hour of television every day of the week. For those students enrolled in physical education, the actual amount of class time devoted to physical activity has dropped significantly over the past decade. Students spend a majority of time in physical education class standing around, waiting for instructions, or socializing. Teens who are active in school sporting activities are more likely to be active as adults. The bottom line is that behaviors that are initiated in childhood tend to consolidate during adolescence. Therefore, health-related behaviors, such as dietary habits and physical activity patterns, solidify during adolescence and persist into adulthood. Recognition of individuals who are insufficiently active, overweight, or obese during adolescence is important.

Figure 10-1.

Trends in moderate-to-vigorous physical activity and sedentary behaviour among US High School Students, 1999-2005. (From the National Youth Risk Behavior Surveys.)

Chapter disclaimer: The opinions herein are those of the author. They do not represent official policy of the Department of Defense, the Department of the Navy, or the Uniformed Services University.

Gordon-Larsen P et al: Longitudinal physical activity and sedentary behavior trends: adolescence to adulthood. Am J Prev Med 2004;27:277.  [PubMed: 15488356]
Lowry R et al: Recent trends in participation in physical education among US high school students. J Sch Health 2001;71:145.  [PubMed: 11357870]
NHANES data on the Prevalence of Overweight Among Children and Adolescents: United States, 2003–2006. ...

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