Physical Activity
Physical activity expends energy, which balances energy consumed and maintains normal weight. Increased physical activity is associated with lower risks for chronic diseases; cardiovascular diseases, such as coronary heart disease and hypertension and other conditions, such as colon cancer and diabetes.[41] Increased levels of physical activity are recommended, as this has been associated with lower risk for premature death. For children and adolescents, regular physical activity not only helps to control weight but also improves strength and endurance, builds healthy bones and muscles, reduces stress, and increases self-esteem.[41] However, levels of physical activity in childhood have declined in recent years, concomitant with the increased focus on academic achievement in schools and the increased use of electronic media and Internet at home.
The obesity epidemic is related to lower levels of physical activity among children compared with the evidence-based recommendations. Children and adolescents aged 6-17 years should be physically active 60 minutes or longer every day, according to the 2008 Physical Activity Guidelines for Americans from the US Department of Health and Human Services.[42] Moderate or vigorous aerobic physical activity is recommended in the guidelines, on the basis of a thorough review of the scientific literature. Children and adolescents should also engage in vigorous, intensity activity at least 3 days per week, including muscle- and bone-strengthening activity at least 3 days per week, according to recommendations.[42]
One of the traditional avenues for childhood physical activity is physical education and sports at school. However, large population surveys of actual behavior recently reported by the CDC indicate that only 18% of high school students participate in physical activity at least 60 minutes a day, and 33% participate in physical education classes each day.[27] Information from Healthy People 2010 on physical education and activity in schools in 1999, 2005, and 2007 also demonstrate that national goals have not been reached. For many of the measures of physical activity among adolescents (grades 9-12), levels of physical activity have remained the same or have decreased slightly (Table 3).[43]