Why are so many children in the U.S. overweight? The simple answer is that they are eating too much while moving too little. If you consume more calories than you burn, you gain weight. The childhood obesity epidemic is due to both inadequate physical activity among U.S. children and to excess caloric intake, which has been documented as having increased from 1977 to 1996, particularly in adolescents.1, 2
This section explores the specific eating and activity behaviors of children that research has linked to increased risk of obesity. Note that many of these behaviors have changed in recent years not because of a change in personal responsibility or willpower but because our food and activity environment has changed, as we'll discuss later.
The average child or adolescent watches nearly 3 hours of TV a day.3 The amount of time spent watching television is directly correlated with obesity, as the graph shows.4, 5 More importantly, reducing TV time through educational interventions has been shown to be an effective way to reduce childhood obesity.6, 7
TV viewing is thought to impact obesity through diet as well as inactivity. The average child watches nearly 10,000 food and beverage TV commercials a year.8 The more children watch TV, the more they request the foods they see advertised, the more of these their parents buy, and the more calories children consume.9 Additionally, many kids associate TV viewing with eating and may overeat while watching TV because they are distracted and don't realize when they're full.10
Moving Too Little
Regular physical activity, whether structured or unstructured, is associated with a reduced risk of childhood obesity.11 However, almost two-thirds of 9- to 13-year-olds (three-quarters of Hispanic and African-American children) participate in no organized physical activities outside of school, and more than 1 in 5 engage in no physical activity in their free time.12 Only 1 in 8 children walk or bike to school. Kids spend a lot of time in sedentary activities such as video and computer games and little time in active play or outside, in part due to unsafe neighborhoods, parental absence due to work, and long commutes for both parents and their children. Additionally, physical education and recess in schools has been cut back to make more time for academics.
Sweetened Beverages: Trends
Consumption of sweetened beverages is a major contributor to childhood obesity. This includes not only soda but also fruit-flavored and fruit juice drinks, iced tea, lemonade, and sports drinks. Consumption of sweetened beverages increased in teens by over 200% from 1965 to 1996, while milk consumption decreased by 36%.13 On average, teen boys get 11% of their daily calories from sweetened beverages.
Sweetened Beverages and Weight Gain
Teens who regularly drink sugar-sweetened beverages consume as many as 200 calories more per day than those who drink other beverages.14 More importantly, one study found that for every additional serving of sugar-sweetened drinks consumed by children, the odds of their becoming overweight increased by 60%.15 Sweetened drinks may be easy to overconsume because calories from sugar in liquid form may be less well compensated for by a decrease in calories consumed later in the day than calories from sugar in solid form.16
Some studies have also linked unsweetened 100% juice to childhood obesity,17 and although this relationship is less clear, it stands to reason that too much juice can lead to too many calories just like anything else. Therefore the American Academy of Pediatrics recommends limiting juice consumption to 6 oz/day for 1-6 year olds and 12 oz/day for 7-18 year olds.18
Excessive portion size is thought to contribute to childhood obesity by promoting overconsumption, particularly for energy-dense foods. Single-serving beverage containers, restaurant servings, and portions at home have all increased.19 For example, today's typical bottle of soda has 165 more calories than 20 years ago, muffins have 290 more calories, and theater popcorn has 360 more calories.20 When children over age 4 (and adults) are offered larger portions, they tend to eat more regardless of their actual hunger.21
High-Fat and Fast Food
Another culprit is high-fat and high-calorie foods such as those commonly found at fast food restaurants. Eating high-fat fast food tends to encourage excess caloric intake, because fast food tends to pack a lot of calories into a small volume, whereas the amount we eat tends to be driven by the volume of what we see before us, not its caloric density. Research shows that children eat more calories on days when they eat fast food.22 When combined with supersizing, it's easy for kids to get almost all the calories they need for a whole day in one fast food meal.
You might think that skipping breakfast is a way to reduce calorie intake, but research shows that children who skip breakfast are more likely to be overweight.23, 24 And, unfortunately, more and more children are skipping breakfast, particularly teenagers. Surveys show that about 1 out of 5 younger teens and a third of older teens regularly skip breakfast.25
Fruit, Vegetables, Dairy, and Fiber
Diets rich in fruits, vegetables, dairy products, and fiber may help to prevent excessive weight gain in children (and also in adults).26 However, fewer than one in four 6-11 year olds meet national recommendations for either vegetables or fruits, only about a third meet them for dairy products, and children this age eat less than one serving per day of whole grains.27 Teens don't do any better.
Multiple Small Changes Are Needed
Anyone (child or adult) who habitually consumes 100 calories more than is burned each day will gain an excess of about 10 pounds in a year. 100 calories is equal to 1 cup of soda or fruit drink or 4 chocolate kisses, so it's easy to get out of balance. On the other hand, moving for about half an hour a day (not hard for most kids, if given the opportunity) burns about 100 calories, which can reduce excessive weight gain by 10 pounds in a year. Therefore focusing on multiple small, achievable changes in both diet and activity can really make a difference. Together, such changes can make it relatively easy to get back in balance.
A Note of Caution: Approach Is Critical
Many people think only overweight children are practicing unhealthy lifestyles. In fact, most of our children have unhealthy lifestyles—overweight children are the ones who show it early on.
Therefore, successful interventions need to focus on lifestyle, not on weight, and on all kids, not just those already overweight. All kids benefit from being more active and eating well, and a focus on weight can cause increased stigmatization, lower self-esteem, eating disorders, and unhealthy dieting, all of which are on the rise. More importantly, it's largely inactivity and poor eating habits that contribute to disease, so interventions need to focus on these.
We also need to look beyond behavior. Kids are eating more fast food and soda, skipping breakfast, and watching TV at increasing rates. What has changed that is driving these behaviors?
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2 Enns C, Mickle S, Goldman J. Trends in food and nutrient intakes by adolescents in the United States. Fam Econ and Nutr Rev. 2003;15(2).
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20 National Institute of Health. Portion Distortion!. Available at: http://hin.nhlbi.nih.gov/portion/index.htm. Accessed December 5, 2005.
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