Heredity and environment play key roles in determining a child's risk of becoming overweight or obese. If one parent is obese, then there is a 50% chance that a child will be obese, and when both parents are obese, a child has an 80% chance of being obese. While there is mounting evidence of genetic predisposition and susceptibility to overweight and obesity, childhood obesity is still considered largely an environmental problem—the result of behaviors, attitudes, and preferences learned early in life. Children's relationships with food develop in response to family and cultural values and practices as well as the influences of school, peers, and the media.
The question remains—which environmental factors have given rise to the increasing prevalence of overweight children and teens during the past three decades? Many observers point to reliance on fat-laden convenience and fast foods along with time spent watching television, playing video games, and surfing the Internet instead of outdoor, physical activities. In 2003, 60% of female high school students and 73% of male high school students engaged in the recommended amount of moderate or vigorous physical activity. Figure 4.6 shows that the percentages of adolescents who obtained the recommended levels of physical activity decreased by grade throughout high school with just over half (51.6%) of twelfth-grade girls engaging in regular physical activity. Television viewing, media advertising, dwindling school physical education programs, neighborhoods where it is unsafe for children to play outdoors, and even working mothers have been implicated.
Working parents have been accused of a variety of nutritional and parenting infractions that have contributed to children's overindulgence in unhealthy foods. First, they leave children unsupervised and unable to satisfy their hunger with anything except cookies, chips, and soda. Some observers speculate that these children are starved emotionally—for time and atten-tion—as well as nutritionally. They also may be hungry for information, because while many adolescents are responsible for choosing and preparing their own food, they are often unprepared to make healthy choices.
FIGURE 4.6 High school students engaging in regular physical activity by sex, race and Hispanic origin, and grade, 2003
Eating alone, in front of a television or computer, kids are more likely to overeat because they are lonely, bored, or susceptible to advertising cues. Overcome with guilt because they are not home to prepare meals, some working parents may intensify the problem by indulging their children with too many food treats. Stay-at-home parents do not necessarily convey healthier attitudes about food, eating, and nutrition than parents who work outside the home. Both groups may use food, especially sweets, to reward good behavior or may pressure children to clean their plates. Though these suppositions remain unproven, it is known that parents with eating disorders, obsessive dieters, and those with unhealthy eating habits are powerful, negative role models for children.
Children's Diets Receive Failing Grades
Most studies of children's nutrition reveal diets that are too high in fat, saturated fat, and sodium and too low in fiber. According to the U.S. Department of Agriculture (USDA), in 2001 just 16% of children met the recommended intake—10%—of saturated fat (Changes in Children's Diets: 1989–1991 to 1994–1996, January 2001). From 1989 to 1997, children's diets increased by about eighty to 230 calories per day, and most of these additional calories were derived from sugar-laden foods and beverages. Soft drink consumption rose by 40% between 1989 and 1996, from one to 1.4 servings per day. Depending on age and gender, from 56% to 85% of children drink soft drinks each day. Several studies have confirmed that children who drink soft drinks consume from fifty-five to 245 more calories per day than those who do not drink soft drinks. Worse still, soft drinks often replace healthy beverages such as low-fat milk or juice in children's diets. In 2001 just 30% of children had the recommended number of servings of milk per day—a 10% drop since 1989. Only 15% ate the recommended five or more servings of fruits and vegetables each day.
Between-meal snacking by teenagers also increased from 1.6 per day in 1977 to two per day in 1996 ("Taming Obesity: How Important Is the 'Snack Factor'?" http://nutrition.ucdavis.edu/perspectives/JanFeb02.htm). Snacking accounts for about 610 calories per day, up from 460 in 1977. Eating out at restaurants has also served to increase children's caloric consumption. In 1970 Americans spent about one-quarter of their food dollars on dining out. By 2001 the percent of food dollars devoted to dining out had nearly doubled, and children derived about one-third of their daily caloric intake from foods prepared outside the home—restaurant or take-out foods. One study, "Children's Patterns of Macronutrient Intake and Associations with Restaurant and Home Eating" (Journal of the American Dietetic Association, August 2001), found that when children ate meals at restaurants, they consumed nearly twice the calories they would consume at home. The study's authors, including Christine Zoumas-Morse, also reported that when children ate at restaurants they consumed more saturated fat than when they ate meals and snacks at home.
Results from the Youth Risk Behavior Surveillance
The Youth Risk Behavior Surveillance System is a national school-based survey conducted by CDC as well as state and local school-based surveys performed by education and health agencies. It examines health-risk behaviors among youth and young adults, including unhealthy dietary behaviors, physical inactivity, and overweight. This section summarizes key dietary findings from the national survey of students in grades nine through twelve conducted between February and December 2003.
TABLE 4.4 Percentage of high school students who had eaten fruits and vegetable ≥5 times/day and who had drunk ≥3 glasses/day of milk, by sex, race/ethnicity, and grade, 2003
| TABLE 4.4 | ||||||
|---|---|---|---|---|---|---|
| Percentage of high school who had eaten fruits and vegetables ≥5 times/day and who had drunk ≥3 glasses/day of milk, by sex, race/ethnicity, and grade, 2003 | ||||||
| Category | Ate fruits and vegetables ≥5 timesa | Drank ≥3 glasses/day of milkb | ||||
| Female | Male | Total | Female | Male | Total | |
| Percent | Percent | Percent | Percent | Percent | Percent | |
| aHad consumed 100% fruit juice, fruit, green salad, potatoes (excluding french fries, fried potatoes, or potato chips), carrots, or other vegetables ≥5 times/day during the 7 days preceding the survey. | ||||||
| bHad drunk ≥3 glasses/day of milk during the 7 days preceding the survey | ||||||
| cNon-Hispanic. | ||||||
| SOURCE: Jo Anne Grunbaum et al., "Table 48. Percentage of High School Students Who Had Eaten Fruits and Vegetables ≥5 Times/Day and Who Had Drunk ≥3 Glasses/Day of Milk, by Sex, Race/Ethnicity, and Grade—United States, Youth Risk Behavior Survey, 2003," in "Youth Risk Behavior Surveillance—United States, 2003," in Morbidity and Mortality Weekly Report Surveillance Summaries, vol. 53, No. SS-2, Centers for Disease Control and Prevention, National Center for Health Statistics, May 21, 2004, http://www.cdc.gov/mmwr/preview/mmwrhtml/ss5302a1.htm#tab48 (accessed September 27, 2005) | ||||||
| Race/ethnicity | ||||||
| Whitec | 19.6 | 21.2 | 20.5 | 12.8 | 26.8 | 20.0 |
| Blackc | 20.3 | 26.1 | 23.2 | 7.5 | 16.0 | 11.6 |
| Hispanic | 21.5 | 27.4 | 24.4 | 9.0 | 17.0 | 13.1 |
| Grade | ||||||
| 9 | 21.2 | 25.3 | 23.3 | 13.5 | 25.1 | 19.5 |
| 10 | 22.7 | 23.1 | 23.0 | 11.8 | 23.8 | 17.9 |
| 11 | 18.3 | 24.5 | 21.4 | 9.8 | 22.6 | 16.4 |
| 12 | 18.1 | 20.8 | 19.5 | 8.9 | 18.1 | 13.6 |
| Total | 20.3 | 23.6 | 22.0 | 11.2 | 22.7 | 17.1 |
Just one-fifth (22.0%) of students had eaten fruits and vegetables at least five times a day during the seven days preceding the survey. (See Table 4.4.) More male (23.6%) than female (20.3%) students reported having eaten fruits and vegetables five or more times per day. Overall, the prevalence of having eaten fruits and vegetables at least five times a day was higher among Hispanic (24.4%) than white (20.5%) students and higher among African-American male (26.1%) and Hispanic male (27.4%) than white male (21.2%) students. Similarly, the prevalence of having eaten fruits and vegetables at least five times a day was higher among younger students and decreased with age—ninth grade (23.3%), tenth grade (23%), eleventh grade (21.4%), and twelfth grade (19.5%).
Even fewer students (17.1%) had drunk at least three glasses of milk per day than had eaten the recommended servings of fruit and vegetables during the seven days preceding the survey. (See Table 4.4.) Overall, more white (20%) than African-American (11.6%) and Hispanic (13.1%) students had three or more glasses a day of milk during the seven days preceding the survey. The prevalence of having drunk at least three glasses of milk per day was higher among male (22.7%) than female (11.2%) students; higher among white male (26.8%), African-American male (16.0%), and Hispanic male (17.0%) than white female (12.8%), African-American female (7.5%), and Hispanic female (9.0%) students. Like fruit and vegetable consumption, the prevalence of drinking three or more glasses a day of milk was higher among younger students and decreased with age. Among male students, the rates were: ninth grade, 25.1%; tenth grade, 23.8%; eleventh grade, 22.6%; and twelfth grade, 18.1%. Among female students, the rates were even lower: ninth grade, 13.5%; tenth grade, 11.8%; eleventh grade, 9.8%; and twelfth grade, 8.9%.
Is Fast Food to Blame?
A staggering one-third of U.S. children eat fast food on any given day, consuming extra calories, sugar, and fat in the process. Shanthy A. Bowman and her colleagues looked at the diets of a representative sample of 6,212 children and teens. They found that boys, adolescents, and children who were African-American, of higher-income families, or from the South were most likely to eat fast food. However, children of all races, incomes, and U.S. regions commonly consumed fast-food meals. The researchers found that on a typical day, more than 30% of U.S. children ages four to nineteen ate burgers, fries, and other fast-food fare. In "Effects of Fast-Food Consumption on Energy Intake and Diet Quality among Children in a National Household Survey" (Pediatrics, vol. 113, no. 1, January 2004), the researchers found that children who ate fast food consumed an average of 187 more calories than did those who did not eat fast food, and, on average, children ate 126 extra calories on the days they ate fast food, compared with fast food-free days. In addition to consuming additional calories, children who ate fast food ingested more sugars, fats, and carbohydrates, while ingesting less fiber, fruits, vegetables, and milk than other children. The researchers calculated that the extra fast-food calories could result in an additional six pounds of weight gain in a year.
To determine how much soda and fast food California teenagers consume, researchers at the University of California, Los Angeles Center for Health Policy Research analyzed data from 4,000 twelve- to seventeen-year-old participants in the 2003 California Health Interview Survey. They found that more than two million California teens—about two-thirds of the total teen population in the state—drink soda every day and about 1.5 million eat fast food daily. The average California teen drinks 1.4 sodas per day, and consumption of soda and other sugary beverages increases with age. Seventeen-year-olds reported drinking 40% more soda (1.7 per day) than twelve-year-olds (1.2 per day). Teenage boys drink about 25% more soda and sweet drinks than do teenage girls, and African-American teens drink the most—averaging two sodas per day. Soda consumption declines with increasing household income. Teens with household income below 300% of the federal poverty limit drink more soda (1.5 to 1.6 per day) than teens from more affluent homes. Soda consumption was 25% higher among teens who said that sodas were available in school vending machines.
Nearly half (48%) of the state's teens eat fast food every day, and many eat fast food more than once a day. Almost 10%—more than 300,000 California teens—have fast food twice a day, and 90,000 eat fast food three or four times a day. As with soda consumption, more teens from low- and moderate-income homes eat fast food every day, and daily fast food consumption increases with age from 43.7% of twelve-year-olds to more than half (51.9%) of seventeen-year-olds. The researchers found that less than one-quarter of California teens eat the recommended five servings of fruit and vegetables each day. Not surprisingly, they also found a relationship between fast food consumption and eating the recommended servings of fruits and vegetables. The more often teens ate fast food the less likely they were to eat fruits and vegetables. Significantly more teens who said they did not eat fast food ate five or more servings of fruit and vegetables per day (Theresa A. Hastert et al., "More California Teens Consume Soda and Fast Food Each Day than Five Servings of Fruits and Vegetables," UCLA Health Policy Research Brief, September 2005).
Researchers at Children's Hospital in Boston think that proximity to fast food encourages children and teens to choose it. The researchers found that about 80% of U.S. teens attend schools within a ten-minute walk of one or more fast food vendors. The location of fast food outlets near schools throughout the nation may be intentional—enabling them to market directly to students as they commute to and from school, and at lunchtime. According to the CDC, about 20% of students do not even have to leave school to purchase fast food—Pizza Hut, Little Caesars pizza, Burger King, and McDonald's hamburgers are readily available in school cafeterias as are chips, candy, and sodas.
The Role of the Media
Despite recent television and print media anti-obesity campaigns, many industry observers condemn corporate marketing efforts and media for continuing to assault children with unhealthy messages that encourage them to eat junk foods. The CDC defines junk foods as those that provide calories primarily through fats or added sugars and have minimal amounts of vitamins and minerals. Michael F. Jacobson, executive director of the Center for Science in the Public Interest (CSPI), a nonprofit nutrition advocacy group based in Washington, D.C., believes that the United States has permitted junk-food marketers—not only fast-food companies, but also makers of sugary cereals and high-fat, high-calorie chips—to target children. In November 2003 he charged that the marketing of fatty, sugary, and low-nutrient foods had reached an all-time high and was fueling childhood obesity, and he called for restricting promotions targeted at the young.
Jacobson observed that even if parents lead by example in terms of healthy eating habits, it is still unfair to allow companies with slick, aggressive, sophisticated advertising campaigns to bypass parents, undermine parental authority, and directly influence children's food choices. Jacobson believes that parents must assume responsibility for ensuring that their children eat healthy meals and snacks; however, he says the marketers and media have an unfair advantage, "Companies are going directly to kids and saying, 'Eat this, eat this, drink this, drink this, it's yummy—you'll love it.' Parents have to say 'No, no, no,' and how many parents say no a thousand times?"
In an interview on a CBS news program ("Beware of Junk Food Marketers," The Early Show, CBSnews.com, November 11, 2003), Jacobson decried advertising of unhealthy foods on Saturday morning television and asserted, "Twenty-five years ago, the government tried to get junk food advertising off of children's television, but they were stopped by the toy industry, the food industry, the broadcasting industry and the advertising industry." CSPI has called upon the U.S. Department of Health and Human Services to work with Congress and the Federal Trade Commission to limit junk-food advertising aimed at children. Currently, federal rules do not restrict advertising content to children, only how much time ads can interrupt children's programming—10.5 minutes per hour on weekends and twelve minutes per hour during the week. Jacobson proposed that in view of the overwhelming evidence of the harmful effects of junk foods on American children's health, "It's time to take another crack at that." CSPI also advocates government-sponsored media campaigns that encourage healthy eating and physical activity.
In an interview in the December 10, 2003, issue of the Washington Post, Margo Wootan, a scientist at CSPI, contended that "This wouldn't be a problem if the marketing was promoting healthy foods. Children are exposed to an endless barrage of marketing everywhere they go throughout the day." Research conducted by CSPI found that marketing aimed at children, including marketing of food products, increased from $6.9 billion in 1992 to $15 billion in 2002. The CSPI report Pestering Parents: How Food Companies Market Obesity to Children (Washington, DC: Center for Science in the Public Interest, 2003) found that the spending power of children doubled each decade in the 1960s, 1970s, and 1980s and tripled during the 1990s. By the year 2000, children were spending a full one-third of their money to purchase foods and drinks. Wooten asserted that "Congress should give the Federal Trade Commission the authority and adequate funding to develop and implement (in consultation with the Department of Health and Human Services) nutrition standards for foods that can be advertised and marketed to children." She also criticized the use of fictional characters and real celebrities including classic children's favorites to promote unhealthy eating. Wooten lamented on the CSPI Web site, "SpongeBob Squarepants, Winnie the Pooh, Elmo, and even sports stars like Jason Giambi are enlisted to push low-nutrition foods on kids."
The CSPI report observed that the variety of ways that food companies market to children and teens extends beyond print and electronic media advertising to promotions in schools, in conjunction with manufacturers of books and toys, throughout the entertainment industry, and on the Internet. Examples of such promotions included:
- Pizza Hut rewards students who read a specified number of books with a coupon that entitles them to free Personal Pan Pizzas. CSPI observed that nutritionists advise parents not to use food to reward or punish children and that some states have prohibited the use of food to reward academic achievement.
- Food brand children's books, such as those published by the makers of M&Ms, Fruit Loops, Skittles, Her-shey Kisses, and Necco Sweetheart candies, often combine reading and eating. For example, the Oreo Cookie Counting Book involves eating ten cookies, which provide 535 calories.
- Web sites aimed at children and teens offer "adver-games" that blend product advertising into arcade game formats. For example, the Nabisco Web site boasts more than fifty games, puzzles, and contests sponsored by specific cookies and other snack foods. Preschoolers can search for Teddy Graham cookies, while older children play an adventure game in which finding Oreo cookie jars restores them to 100% good "health."
- Product placement, in which food manufacturers pay a fee or donate products for inclusion in movies and television programs, is another potent form of subliminal or stealth advertising—promotions that aim below the conscious perception of advertising. The CSPI report cited the appearance of the soft drink Dr. Pepper in the successful 2002 motion picture Spiderman, and McDonald's Big Mac, fries, and soda, along with the trademark golden arches in Spy Kids 2, another popular children's film released in 2002.
Some critics, including Velma LaPoint, professor of childhood development at Howard University in Washington, assert that advertisers exploit normal adolescent susceptibility to peer pressure with subliminal messages telling kids that they are "part of the in-crowd if you're consuming certain foods," and an outcast if you choose to forgo a particular soft drink or snack food (Katrina Woznicki, "Experts Debate Media's Role in Obesity," United Press International, December 10, 2003).
Educators and marketers observe that corporations remain eager to maintain a high-profile presence in schools, which enables them to remain highly visible to students. In 2005 McDonald's launched its "Passport to Play" program, which provides free lesson plans and materials to third- through fifth-grade physical education teachers. McDonald's describes the program, which has been distributed to 31,000 elementary schools nationwide, as reflecting the company's "commitment to balanced, active lifestyles today." Some critics object to commercialism of any kind in the schools, even if the message encourages healthy choices. Others believe that it is hypocritical for purveyors of low-nutrient foods to link these foods to physical fitness or athletic prowess.
The Media Can Deliver Powerful Nutrition and Health Education
During 2005 greater emphasis on children's diets inspired media efforts to offer nutrition education. Rather than subsisting on a diet of cookies alone, Sesame Street's Cookie Monster has begun championing healthy food choices. The beloved character is singing a new tune, "A Cookie Is a Sometimes Food." SpongeBob SquarePants, who in the past appeared on Breyer's ice cream cartons and Kellogg's sweetened cereals, has relocated to the produce section and is advocating fresh produce consumption. Along with SpongeBob Square-Pants, Dora the Explorer and other Nickelodeon characters appear on packages of fruit and vegetables, under licensing agreements with produce companies. Clifford the Big Red Dog promotes an organic cereal with his name and likeness and Arthur the aardvark has loaned his name and likeness to Arthur's Loops, another organic cereal.
Recent entries to children's television programming such as Jo Jo's Circus on Disney and Nickelodeon's Lazy Town aim to inspire young viewers to be physically active. Blending fitness and entertainment, video game makers have developed a genre of active rhythm games including Dance Dance Revolution, which features a workout mode that can track how many calories the user burns while playing. In the Groove and Pump It Up: Exceed are videogames in which players try to match the onscreen action by stepping on different sections of a floor pad, and Yourself!Fitness and Kinetic offer teens exercise routines in videogame formats.
Escape from Obeez City is an interactive DVD game that teaches children about the dangers of poor nutrition and inactivity, motivating them to change their behavior. Although Escape from Obeez City was developed by a company in Australia, the National Institutes of Health is funding videogame research projects in the United States as part of its anti-obesity efforts.
Although industry observers concede that the media can have a powerful and favorable effect on children's knowledge and awareness of healthy choices in terms of diet and exercise, many health professionals believe that television and video games alone will not solve the problems of childhood overweight, obesity, and inactivity. They assert that a concerted effort of families, schools, health professionals, food vendor, and the media is necessary to create the far-reaching cultural changes needed to modify children's diet and exercise habits. According to Tom Robinson, an associate professor of pediatrics at Stanford University ("Fat Is the Villain Here in 'Obeez City,'" Los Angeles Times, July 11, 2005), "If I had to choose between buying a child one of these active games or removing the TV from their bedroom and setting weekly TV time limits, I would strongly favor the latter."
Many Schools Offer Unhealthy Food Choices
Food manufacturers and marketers know that schools are ideal sites to promote their products to children and teens. Nearly all youth attend school and spend many of their waking hours at school. Further, the presence of foods in schools allows food companies to benefit from the implied endorsement of the schools and teachers. According to the CDC in Competitive Foods and Beverages Available for Purchase in Secondary Schools—Selected Sites, United States, 2004, nearly all high schools (98%), three-quarters of middle schools (74%), and 43% of elementary schools have vending machines, stores, or snack bars on campus that sell "competitive foods"—foods that are not part of federally reimbursable school meals. Figure 4.7 shows the types and sources of competitive foods in schools. The nutritional value of competitive foods is essentially unregulated, and students often purchase these foods instead of, or in addition to, school meals. In 2004 the majority (percentages ranged from 59.8% to 95% across states) of public secondary schools in twenty-seven states and eleven large urban school districts allowed the sale of less-nutritious competitive foods—snack food and beverages such as candy, soft drinks, salty snacks that are not low in fat, and cookies—from vending machines, snack bars, and cafeterias on the school campuses.
The CDC found considerable differences between the states and cities in the amount of junk food available in schools. Maine, Massachusetts, Connecticut, New Hampshire, and Texas had made the greatest strides in terms of reducing the amount of junk foods sold in their schools. In contrast, Oklahoma, Utah, and Washington offered the most non-nutritious foods and beverages. Table 4.5 shows that many more schools offer less-nutritious foods and beverages than healthier choices such as low-fat salty snacks and baked goods, fruit and vegetables. For example, 18.5% of Oklahoma schools offer fruits and vegetables, while 88.9% offer chocolate candy. In Connecticut 57.8% of schools offer fruits and vegetables, while 38.3% sell chocolate candy.
In addition to selling food in schools, food manufacturers advertise on vending machines, posters, book covers, scoreboards, and banners and offer schools educational materials, contests in which children receive prizes or food rewards for achievement, and fundraising opportunities. Some critics, including CSPI, assert that the manufacturers are taking unfair advantage of cash-strapped school districts. The National Association of State Boards of Education takes direct aim at these relationships between businesses and schools, decrying "cola wars" in which school districts bargained with franchises to obtain the highest-paying, exclusive marketing-rights contracts possible. In exchange for "pouring rights"—the exclusive right to sell and promote their products in the schools—the companies may pay the districts in excess of several million dollars. The National Association of State Boards of Education characterizes these relationships as "exploitation and a violation of the public trust."
A review prepared by Jim Bogden of the National Association of State Boards of Education, State Policies on the Sale of Food and Beverages at School, 2001 revealed that thirty-three states and territories simply administered USDA regulations governing school food programs that prohibit "foods of minimal nutritional value" from being sold in food service areas during meal times. The USDA definition of "foods of minimal nutritional value" (FMNV) does not include many popular high-fat snacks such as potato chips, tortilla chips, cheese
FIGURE 4.7 Categories and sources of competitive foods in schools
SCHOOLS SELL COMPETITIVE FOODS AND OBTAIN SUBSTANTIAL REVENUES FROM THEIR SALE
In 2004 a report from the U.S. Government Accountability Office (GAO) found that several states had enacted competitive food policies more stringent than those required by federal regulations. The policies and practices, however, varied widely. In 2005 the GAO analyzed data from two nationally representative surveys to determine the prevalence of competitive foods in schools, the groups involved in their sale, restrictions on competitive foods, and the amounts and use of revenue generated by their sale. In August 2005 the GAO issued its findings in School Meal Programs: Competitive Foods Are Widely Available and Generate Substantial Revenues for Schools.
The GAO analysis found that nearly all schools sold competitive foods during the 2003–04 school year, with middle schools and high schools more likely than elementary schools to offer competitive foods. Table 4.6 shows the percentages of elementary, middle, and high schools selling competitive foods via a la carte lines, vending machines, and school stores. In one-third of schools, sweet baked goods, salty snacks, and other less-nutritious foods were available in cafeteria snack lines. Schools often sold competitive foods at lunchtime, in the cafeteria or nearby, allowing kids to buy them for lunch or to supplement their lunches. Table 4.7 categorizes the types of competitive foods—nutritious, neither clearly nutritious nor less nutritious, and less
TABLE 4.5 Percentage of public secondary schools allowing students to purchase foods and beverages and the percentage offering selected types of foods and beverages, by state or school district, 2004
| TABLE 4.5 | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Percentage of public secondary schools allowing students to purchase foods and beverages and the percentage offering selected types of foods and beverages, by state or school district, 2004 | ||||||||||
| State | Schools allowing Purchases from vending machines store, canteen, or snack bar (percent) | |||||||||
| Less nutritious foods and beverages | More nutritious foods and beverages | |||||||||
| Chocolate candy (percent) | Other kinds of candy (percent) | Salty snacks not low in fat (percent) | Soft drinks, sports drinks, or fruit drinks not 100% juice (percent) | Fruits or vegetables (percent) | Salty snacks low in fat (percent) | Low-fat baked goods (percent) | 100% fruit juice (percent) | Bottled Water (percent) | ||
| *Survey did not include schools from one of the state's largest school districts. | ||||||||||
| SOURCE: L. Kann et al., "Table. Percentage of Public Secondary Schools Allowing Students to Purchase Foods and Beverages from Vending Machines or at the School Store, Canteen, or Snack Bar and, among Those Schools Allowing Purchases, the Percentage Offering Selected Types of Foods and Beverages, by State or School District—School Health Profiles, United States, 2004," in "Competitive Foods and Beverages Available for Purchase in Secondary Schools—Selected Sites, United States, 2004," in Morbidity and Mortality Weekly Report, vol. 54, no. 37, Centers for Disease Control and Prevention, National Center for Health Statistics, September 23, 2005, http://www.cdc.gov/mmwr/PDF/wk/mm5437.pdf (accessed January 12, 2006) | ||||||||||
| Alaska | 59.8 | 76.5 | 77.0 | 81.6 | 94.3 | 21.5 | 79.6 | 55.6 | 81.6 | 83.9 |
| Arizona | 73.8 | 63.0 | 64.7 | 74.8 | 88.0 | 43.4 | 77.6 | 60.5 | 71.1 | 90.8 |
| Arkansas | 93.8 | 69.7 | 73.7 | 74.3 | 96.6 | 28.4 | 72.5 | 49.7 | 71.9 | 90.3 |
| Connecticut | 81.1 | 38.3 | 41.2 | 72.7 | 88.9 | 57.8 | 82.8 | 63.1 | 85.6 | 93.2 |
| Delaware | 80.5 | 35.6 | 39.9 | 74.5 | 89.2 | 45.0 | 76.8 | 68.4 | 95.5 | 100.0 |
| Idaho | 92.7 | 72.4 | 73.4 | 73.9 | 97.3 | 32.9 | 73.2 | 52.9 | 77.0 | 96.2 |
| Iowa | 89.5 | 66.8 | 67.7 | 71.3 | 97.0 | 43.0 | 71.8 | 60.1 | 87.4 | 94.8 |
| Maine | 91.7 | 40.0 | 45.1 | 61.4 | 78.9 | 50.0 | 79.6 | 68.9 | 94.9 | 100.0 |
| Massachusetts | 85.4 | 35.3 | 40.5 | 73.9 | 86.4 | 51.0 | 79.8 | 58.0 | 86.1 | 94.0 |
| Michigan | 92.1 | 72.3 | 76.0 | 86.2 | 96.8 | 55.0 | 85.8 | 66.2 | 85.9 | 98.9 |
| Minnesota | 91.1 | 78.7 | 80.7 | 83.9 | 95.9 | 46.7 | 88.5 | 69.0 | 87.0 | 96.4 |
| Missouri | 90.2 | 68.6 | 71.1 | 75.9 | 97.2 | 32.6 | 76.1 | 56.8 | 76.3 | 90.5 |
| Montana | 88.8 | 60.1 | 61.9 | 53.5 | 94.5 | 27.4 | 57.5 | 46.0 | 85.9 | 90.4 |
| Nebraska | 84.1 | 61.9 | 63.3 | 61.2 | 99.5 | 24.8 | 61.7 | 53.3 | 82.3 | 93.5 |
| New Hampshire | 91.4 | 34.5 | 39.7 | 68.7 | 85.0 | 54.4 | 80.4 | 61.6 | 83.4 | 98.6 |
| New York | 90.1 | 41.5 | 43.4 | 70.3 | 84.9 | 44.5 | 75.1 | 58.0 | 83.6 | 93.3 |
| North Carolina | 88.4 | 54.9 | 60.0 | 81.8 | 92.4 | 40.4 | 81.1 | 68.2 | 84.2 | 94.8 |
| North Dakota | 77.0 | 61.7 | 62.9 | 56.5 | 96.7 | 21.9 | 55.6 | 41.0 | 83.5 | 98.7 |
| Oklahoma | 92.6 | 88.9 | 90.4 | 88.3 | 98.8 | 18.5 | 85.9 | 60.4 | 56.6 | 90.9 |
| Oregon | 87.6 | 70.9 | 77.6 | 85.2 | 95.4 | 48.0 | 82.8 | 62.9 | 78.3 | 94.9 |
| Pennsylvania | 84.0 | 60.0 | 68.0 | 83.3 | 90.5 | 45.7 | 86.3 | 64.7 | 87.4 | 94.3 |
| South Carolina | 92.1 | 74.1 | 76.5 | 87.0 | 95.8 | 26.9 | 83.8 | 67.1 | 76.5 | 92.1 |
| Tennessee | 90.1 | 73.8 | 78.1 | 80.1 | 96.8 | 27.7 | 78.7 | 59.9 | 75.7 | 93.3 |
| Texas* | 81.1 | 65.0 | 56.0 | 63.9 | 86.2 | 56.3 | 82.8 | 75.2 | 89.5 | 97.8 |
| Utah | 95.0 | 93.4 | 94.4 | 89.4 | 97.6 | 50.5 | 92.5 | 80.2 | 87.0 | 94.1 |
| Washington | 90.7 | 71.6 | 74.7 | 80.3 | 96.6 | 45.6 | 83.9 | 64.1 | 86.1 | 95.6 |
| Wisconsin | 88.4 | 57.9 | 62.6 | 69.0 | 94.0 | 48.6 | 75.2 | 60.6 | 85.7 | 94.8 |
| Median | 89.5 | 65.0 | 67.7 | 74.5 | 95.4 | 44.5 | 79.6 | 60.6 | 84.2 | 94.3 |
| Range | 59.8-95.0 | 34.5-93.4 | 39.7-94.4 | 53.5-89.4 | 78.9-99.5 | 18.5-57.8 | 55.6-92.5 | 41.0-80.2 | 56.6-95.5 | 83.9-100.0 |
| School district | ||||||||||
| Chicago | 33.2 | 31.7 | 33.7 | 53.0 | 79.5 | 34.1 | 50.8 | 48.0 | 81.3 | 83.4 |
| Dallas | 95.8 | 82.4 | 75.9 | 89.2 | 100.0 | 45.8 | 82.5 | 66.4 | 89.1 | 97.8 |
| District of Columbia | 62.4 | 33.4 | 47.9 | 52.4 | 84.7 | 16.0 | 52.4 | 28.5 | 78.3 | 89.2 |
| Los Angeles | 96.1 | 73.5 | 82.5 | 82.6 | 53.4 | 54.0 | 88.1 | 60.0 | 86.6 | 95.6 |
| Memphis | 72.5 | 61.6 | 65.2 | 62.8 | 97.3 | 20.3 | 60.0 | 37.6 | 90.1 | 79.6 |
| Miami | 83.4 | 70.2 | 70.2 | 78.9 | 95.0 | 47.0 | 77.2 | 66.9 | 82.5 | 84.9 |
| New Orleans | 81.5 | 70.0 | 77.4 | 81.1 | 92.6 | 14.7 | 66.5 | 65.2 | 61.7 | 100.0 |
| Orange County | 86.3 | 58.0 | 62.3 | 85.8 | 87.2 | 61.4 | 83.5 | 66.5 | 84.3 | 100.0 |
| Philadelphia | 71.3 | 35.2 | 47.3 | 81.8 | 83.1 | 45.9 | 76.2 | 55.7 | 90.1 | 88.6 |
| San Bernardino | 81.3 | 27.3 | 41.7 | 91.7 | 100.0 | 66.7 | 83.3 | 75.0 | 83.3 | 100.0 |
| San Diego | 92.8 | 47.9 | 48.1 | 89.6 | 92.1 | 77.1 | 84.6 | 65.5 | 71.9 | 97.4 |
| Median | 81.5 | 58.0 | 62.3 | 81.8 | 92.1 | 45.9 | 77.2 | 65.2 | 83.3 | 95.6 |
| Range | 33.2-96.1 | 27.3-82.4 | 33.7-82.5 | 52.4-91.7 | 53.4-100.0 | 14.7-77.1 | 50.8-88.1 | 28.5-75.0 | 61.7-90.1 | 79.6-100.0 |
The analysis revealed that the during the period 1998–99 and 2003–04, the availability of competitive food venues in middle schools rose from 83% to 97%. During the same period, the number of middle schools with exclusive beverage contracts and the number of vending machines per school also increased. Three-quarters of high schools had exclusive soft drink contracts, and 65% of middle schools had exclusive beverage contracts in 2004, up from 26% five years before. Similarly, the volume and variety of competitive foods sold increased in more than two-thirds of high schools, more than half
FIGURE 4.8 States that have made efforts to restrict competitive foods in schools beyond USDA regulations, as of April 2005
Many different groups were involved in school food sales—students, parent-teacher associations, and booster groups as well as food services participated in competitive food sales. Generally, the number of groups involved and sales venues increased from elementary to middle school, with the most participants at the high school level. Figure 4.9 displays the groups and venues typically involved in competitive food sales in high schools.
In 2003–04, schools generated considerable revenues through competitive food sales, particularly middle schools and high schools. The top 29% of high schools, in terms of sales, generated in excess of $125,000 per school. (See Figure 4.10.) The analysts also found that all the school districts they examined had taken action to substitute healthy foods for less-nutritious competitive foods. The districts acknowledged that chief among obstacles to enacting these changes was concern about revenue losses.
Food for Thought Has New Meaning at Many Schools
As of September 2005 forty-two state legislatures had enacted or proposed measures that required or recommended nutritional guidance for schools. The 2004 reauthorization of the federal Child Nutrition Act requires every school district that receives federal funds to establish a local wellness policy by June 30, 2006, and
TABLE 4.6 Estimated percentage of schools of different levels with each competitive food venue, 2003–04
| TABLE 4.6 | |||
|---|---|---|---|
| Estimated percentage of schools of different levels with each competitive food venue, 2003–04 | |||
| Elementary school | Middle school | High school | |
| SOURCE: "Table 2. Estimated Percentage of Schools of Different Levels with Each Competitive Food Venue in 2003–2004," in School Meal Programs: Competitive Foods Are Widely Available and Generate Substantial Revenues for Schools, U.S. Government Accountability Office, August 2005, http://www.gao.gov/new.items/d05563.pdf (accessed January 12, 2006) | |||
| A la carte | 67 | 88 | 91 |
| Vending machines | 46 | 87 | 91 |
| School stores | 15 | 25 | 54 |
| One or more of the above venues | 83 | 97 | 99 |
| TABLE 4.7 | |||
|---|---|---|---|
| Type of competitive foods often or always available through any venue in schools, by school level and nutrition category | |||
| Elementary school | Middle schools | High schools | |
|
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|
|
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|
|
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| ▴ Item is estimated to be available in approximately half or more schools with any venue | |||
| ◯ Item is estimated to be available in approximately one-third or more schools with any venue | |||
| Note: The nutrition categories, as signified by the shading, are general descriptions of the foods in each category. Nutritional content can vary depending on the ingredients and the methods used to prepare foods. | |||
| SOURCE: "Table 4. Types of Competitive Foods Often or Always Available through Any Venue in Schools, by School Level and Nutrition Category," in School Meal Programs: Competitive Foods Are Widely Available and Generate Substantial Revenues for Schools, U.S. Government Accountability Office, August 2005, http://www.gao.gov/new.items/d05563.pdf (accessed January 12, 2006) | |||
| Water | ▴ | ▴ | ▴ |
| Milk, 1% or skim | ▴ | ▴ | ▴ |
| Milk, whole or 2% | ▴ | ▴ | ▴ |
| 100% juice | ▴ | ▴ | ▴ |
| Fruit | ▴ | ▴ | ▴ |
| Vegetables and/or salad | ▴ | ▴ | ▴ |
| Yogurt | ◯ | ▴ | |
| Less than 100% juice | ◯ | ▴ | ▴ |
| Sports drinks | ▴ | ▴ | |
| Low-fat salty snacks | ▴ | ▴ | |
| Low-fat sweet baked goods | ◯ | ▴ | |
| Low-fat frozen desserts | ◯ | ||
| Sandwiches | ▴ | ▴ | ▴ |
| Pizza | ▴ | ▴ | |
| Fried vegetables | ◯ | ||
| Frozen desserts (not low-fat) | ◯ | ▴ | |
| Salty snacks (not low-fat) | ▴ | ▴ | |
| Sweet baked goods (not low-fat) | ▴ | ▴ | |
| Candy | ◯ | ▴ | |
| Soda | ◯ | ▴ | |
Seattle's 100 public schools became "junk-food free" in 2004, and Arkansas took action to remove vending machines from elementary schools and require reporting of revenue from competitive food sales. In Buffalo, New York, schools are giving prizes to kids who eat lots of fruits and vegetables; and in schools in Sarasota, Florida, whole wheat bread and veggie pita sandwiches accompany several salad options.
Connecticut was the first state to pass a ban on selling sugar-sweetened sodas in schools. Similar bills have been introduced in seventeen other states. In July 2004 schools in Philadelphia, Pennsylvania, instituted a no-soda policy, and on September 15, 2005, California Governor Arnold Schwarzenegger signed legislation banning the sale of soda in state high schools.
New Jersey schools are adopting what may prove to be the most ambitious new statewide school nutrition policy in the nation. By 2007 all of the state's public schools must comply with a policy stipulating that soda, any food item listing sugar as its first ingredient, all forms of candy, and foods of minimal nutritional value (per the USDA definition) cannot be served, sold, or given for free anytime during the school day. Snacks and drinks sold anywhere on a school campus must have no more than 8 grams of fat and 2 grams of saturated fat per serving, and drinks cannot exceed more than 12 ounces, except bottled water. The policy applies to vending machines, cafeterias, a la carte items, school stores, school fundraisers, and the after-school snack program. The policy also makes nutrition education a requirement in school curricula.
Along with revamped food services, as of September 2005, five states—Arkansas, California, Florida, Missouri, and Pennsylvania have begun to collect BMI data during student growth screenings. In Pennsylvania, where 35% of children are overweight or at risk for overweight, BMI measurement will be required for students up to eighth grade in 2006, and for all students in the 2007–08 school year.
FIGURE 4.9 Groups most frequently involved in various competitive food venues commonly available in high schools
High School Physical Education Programs
School physical education programs, especially high school programs, have been found as lacking as school nutrition programs. In July 2005 a panel of national obesity experts convened by the CDC determined that children should get an hour of exercise over the course of each day. Yet CDC data reveal that participation in high school physical education classes declined by more than 10% between 1991 and 2003, and more than a third of high school students nationwide do not engage in vigorous physical activity ("Participation in High School Physical Education: United States, 1991–2003," Morbidity and Mortality Weekly Report, September 17, 2004)
The 2003 Youth Risk Behavior Surveillance System found that nationwide, 55.7% of students went to physical education (PE) classes on one or more days in an average week when they were in school. Enrollment in PE classes was higher among ninth graders (71%) and tenth graders (60.7%) than among students in eleventh grade (45.7%) or twelfth (39.5%). Among students enrolled in PE classes, a little more than three-quarters (80.3%) actually exercised or played sports for more than twenty minutes during an average PE class. (See Table 4.8.)
Less than one-third (28.4%) of high school students attended daily (PE) classes when they were in school.
FIGURE 4.10 Estimated percentage of schools generating different minimum amounts of total competitive food revenue, by school level, 2003–04
TABLE 4.8 Percentage of high school students who were enrolled in physical education (PE) class, attended PE class daily, and spent >20 minutes exercising or playing sports during an average PE class, by sex, race/ethnicity, and grade, 2003
| TABLE 4.8 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Percentage of high school students who were enrolled in physical education (PE) class, attended PE class daily, and spent >20 minutes exercising or playing sports during an average PE class, by sex, race/ethnicity, and grade, 2003 | |||||||||
| Category | Enrolled in physical educatlon classa | Attended physical education class dallyb | Exerclsed or played sports >20 minutes during an average physical education classc | ||||||
| Female | Male | Total | Female | Male | Total | Female | Male | Total | |
| Percent | Percent | Percent | Percent | Percent | Percent | Percent | Percent | Percent | |
| aOn one or more days in an average week when they were in school. | |||||||||
| b5 days in an average week when they were in school. | |||||||||
| cAmong the 55.7% of students enrolled in physical education class. | |||||||||
| dNon-Hispanic. | |||||||||
| SOURCE: "Table 54. Percentage of High School Students Who Were Enrolled in Physical Education (PE) Class, Attended PE Class Daily, and Spent >20 Minutes Exercising or Playing Sports During an Average PE Class, by Sex, Race/Ethnicity, and Grade—United States, Youth Risk Behavior Survey, 2003," in "Youth Risk Behavior Surveillance—United States, 2003," in Morbidity and Mortality Weekly Report Surveillance Summaries, vol. 53, No. SS-2, Centers for Disease Control and Prevention, National Center for Health Statistics, May 21, 2004, http://www.cdc.gov/mmwr/PDF/SS/SS5302.pdf (accessed January 12, 2006) | |||||||||
| Race/ethnicity | |||||||||
| Whited | 51.5 | 55.9 | 53.7 | 23.1 | 26.8 | 24.9 | 76.6 | 85.8 | 81.5 |
| Blackd | 49.3 | 63.1 | 56.0 | 29.0 | 37.1 | 33.0 | 66.7 | 80.0 | 74.0 |
| Hispanic | 56.1 | 61.4 | 58.8 | 34.0 | 39.5 | 36.7 | 73.5 | 82.5 | 78.2 |
| Grade | |||||||||
| 9 | 71.2 | 70.8 | 71.0 | 38.0 | 37.7 | 37.9 | 75.7 | 84.8 | 80.3 |
| 10 | 58.3 | 63.0 | 60.7 | 29.1 | 33.5 | 31.3 | 77.0 | 83.2 | 80.3 |
| 11 | 40.8 | 50.5 | 45.7 | 19.2 | 26.0 | 22.6 | 71.6 | 83.7 | 78.4 |
| 12 | 34.6 | 44.5 | 39.5 | 15.2 | 21.4 | 18.2 | 74.9 | 87.2 | 81.8 |
| Total | 52.8 | 58.5 | 55.7 | 26.4 | 30.5 | 28.4 | 75.3 | 84.5 | 80.3 |
The importance of school PE programs cannot be underestimated, especially in view of the survey finding that one-third (33.4%) of students had not participated in sufficient physical activity during the seven days preceding the survey. The prevalence of insufficient physical activity was higher among females (40.1%) than male (26.9%) students. Overall the prevalence of participation in insufficient activity was higher among African-American (41.2%) and Hispanic (36.5%) than white (31%) students and higher among African-American females (50.4%) than white (37.5%) and Hispanic (42.6%) female students. (See Table 4.9.)
Just two-thirds (62.6%) of students had exercised vigorously for twenty or more minutes, three or more times per week in the seven days preceding the survey. More male (70%) than female (55%) students reported exercising vigorously, and the percentages of students who exercised declined with advancing grades. Almost three-quarters (73.1%) of ninth-grade males reported receiving sufficient vigorous physical exercise compared to only 46.4% of twelfth-grade female students. (See Table 4.10.)
GIRLS' INACTIVITY DURING ADOLESCENCE LEADS TO OBESITY
Decreasing physical activity during adolescence appears to play a major role in weight gain among girls as they grow from children to women. Investigators from several medical centers monitored and analyzed activity and BMI for 1,152 African-American and 1,135 white girls
TABLE 4.9 Percentage of high school students who participated in an insufficient amount of physical activity and no vigorous or moderate physical activity, by sex, race/ethnicity, and grade, 2003
| TABLE 4.9 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Percentage of high school students who participated in an insufficient amount of physical activity and no vigorous or moderate physical activity, by sex, race/ethnicity, and grade, 2003 | |||||||||
| Category | Participated in an insufficient amount of physical ativitya | No vigorous or moderate physical activityb | |||||||
| Female | Male | Total | Female | Male | Total | ||||
| Percent | Percent | Percent | Percent | Percent | Percent | ||||
| aHad not participated in sufficient vigorous physical activity and had not participated in sufficient moderate physical activity during the 7 days preceding the survey | |||||||||
| bHad not participated in either vigorous physical activity or moderate physical activity during the 7 days preceding the survey. | |||||||||
| cNon-Hispanic. | |||||||||
| SOURCE: "Table 52. Percentage of High School Students Who Participated in an Insufficient Amount of Physical Activity and No Vigorous or Moderate Physical Activity, by Sex, Race/Ethnicity, and Grade—United States, Youth Risk Behavior Survey, 2003," in "Youth Risk Behavior Surveillance—United States, 2003," in Morbidity and Mortality Weekly Report Surveillance Summaries, vol. 53, no. SS-2, Centers for Disease Control and Prevention, National Center for Health Statistics, May 21, 2004, http://www.cdc.gov/mmwr/PDF/SS/SS5302.pdf (accessed January 12, 2006) | |||||||||
| Race/ethnicity | |||||||||
| Whitec | 37.5 | 24.8 | 31.0 | 11.1 | 9.3 | 10.2 | |||
| Blackc | 50.4 | 31.8 | 41.2 | 20.0 | 12.6 | 16.3 | |||
| Hispanic | 42.6 | 30.3 | 36.5 | 15.4 | 10.6 | 13.0 | |||
| Grade | |||||||||
| 9 | 32.7 | 23.8 | 28.1 | 9.7 | 8.4 | 9.1 | |||
| 10 | 35.9 | 25.6 | 30.8 | 10.2 | 10.0 | 10.1 | |||
| 11 | 46.2 | 27.0 | 36.5 | 16.7 | 10.8 | 13.7 | |||
| 12 | 48.4 | 32.1 | 40.2 | 17.0 | 10.9 | 14.0 | |||
| Total | 40.1 | 26.9 | 33.4 | 13.1 | 10.0 | 11.5 | |||
| TABLE 4.10 | ||||||
|---|---|---|---|---|---|---|
| Percentage of high school students who participated in sufficient vigorous physical activity and moderate physical activity, by sex, race/ethnicity, and grade, 2003 | ||||||
| Category | Participated in sufficient vigorous physical activitya | Pariticipated in sufficient moderate physical activityb | ||||
| Female | Male | Total | Female | Male | Total | |
| Percent | Percent | Percent | Percent | Percent | Percent | |
| aExercised or participated in physical activities that made students sweat and breathe hard for≥20 minutes on≥3 of the 7 days preceding the survey (e.g., basketball, soccer running, swimming laps, fast bicycling, fast dancing, or similar aerobic activities). | ||||||
| bPhysical activities that did not make students sweat and breathe hard for ≥30 minutes on ≥5 of the 7 days preceding the survey (e.g., fast walking, slow bicycling, skating pushing a lawn mower, or mopping floors). | ||||||
| cNon-Hispanic. | ||||||
| SOURCE: "Table 50. Percentage of High School Students Who Participated in Sufficient Vigorous Physical Activity and Sufficient Moderate Physical Activity, by Sex, Race/Ethnicity, and Grade—United States, Youth Risk Behavior Survey, 2003," in "Youth Risk Behavior Surveillance—United States, 2003," in Morbidity and Mortality Weekly Review Surveillance Summaries, vol. 53, no. SS-2, Centers for Disease Control and Prevention, National Center for Health Statistics, May 21, 2004, http://www.cdc.gov/mmwr/PDF/SS/SS5302.pdf (accessed January 12, 2006) | ||||||
| Race/ethnicity | ||||||
| Whitec | 58.1 | 71.9 | 65.2 | 23.3 | 28.9 | 26.2 |
| Blackc | 44.9 | 65.0 | 54.8 | 17.5 | 25.8 | 21.7 |
| Hispanic | 51.8 | 66.7 | 59.3 | 20.6 | 23.3 | 22.0 |
| Grade | ||||||
| 9 | 63.6 | 73.1 | 68.5 | 22.3 | 28.3 | 25.4 |
| 10 | 58.2 | 71.5 | 64.9 | 25.3 | 26.2 | 25.7 |
| 11 | 49.4 | 70.4 | 60.1 | 20.0 | 28.1 | 24.2 |
| 12 | 46.4 | 63.7 | 55.0 | 20.0 | 26.3 | 23.2 |
| Total | 55.0 | 70.0 | 62.6 | 22.1 | 27.2 | 24.7 |
in San Francisco, Cincinnati, and Washington, D.C., as they grew from ages nine and ten years to eighteen and nineteen (Sue Y.S. Kim et al., "Relationship between Changes in Physical Activity and Body-Mass Index during Adolescence: A Multicentre Longitudinal Study, Lancet, vol. 366, July 23, 2005).
Inactive girls gained an average of ten to fifteen pounds more than girls who were active between the ages of nine and nineteen. The number of calories the subjects consumed increased slightly and did not appear to be associated with the weight gain. Though the investigators found only small differences in BMI between "active" girls and "inactive" girls at the age of nine and ten. (Active was defined as doing the equivalent of at least five brisk, thirty-minute walks each week, while inactive was doing no more than 2.5 thirty-minute walks weekly.) During the following nine years, however, inactive girls had triple the gains in BMI and were about ten to fifteen pounds heavier.
The investigators concluded that their findings "present a strong argument that physical inactivity in this age group is an important contributing factor to the development of obesity." They suggest actions to take to prevent the observed weight gain, such as encouraging teenage girls to add 2.5 hours of brisk walking each week to their schedules.
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