Scene From a Mall: A Study of Teens and Fast Food

An experiment conducted in a mall food court provided information about fast food intake among overweight and lean adolescents (JAMA 2004; 291:2828). Two findings were that teens over-consumed fast food regardless of their body weight, and overweight teens underreported the amount they ate.

Fast food has become a staple of the teenage diet, among all socioeconomic and racial/ethnic groups in the U.S. Thus, it’s no surprise that fast food is heavily marketed to this age group. Now it is estimated that at least three-fourths of teens eat fast food one or more times a week. This increase parallels the escalating rate of obesity in the U.S.

In what is believed to be the first study of the effects of fast food upon overweight and lean teens, researchers at the University of Boston and the University of Minnesota conducted a two-part investigation. First, they fed “an extra large” fast food meal in a naturalistic setting (the food court) to overweight (26) and lean (28) adolescents 13 to 17 years of age. “Overweight” was defined as a body mass index exceeding gender and age-specific 85th percentile levels, based on the 2000 Centers for Disease Control and Prevention growth charts.

The teens were instructed to eat as much or as little as they liked during the 1-hour meal. Participants were grouped by gender and weight to avoid any self-consciousness about eating (for example, girls eating less in the presence of boys and overweight teens eating less in the presence of their lean peers).

In the second part of the study, the researchers assessed the teens’ energy intake under free-living conditions for 2 days when fast food was consumed and 2 days when it was not. Teens were instructed to eat at one of the 5 leading fast food restaurants (McDonald’s, Wendy’s, KFC, Burger King, or Taco Bell). They were instructed to eat at least one menu item containing meat (beef, pork), chicken fish, beans or egg, plus one additional item, such as french fries, a beverage, or dessert. They also had 4 dietary and physical activity recall telephone interviews, and the researchers used a 24-hr dietary recall method, asking the participants to list in sequence the foods and beverages they consumed during the preceding day, with details about each reported item. Physical activity was quantified using a 24-hr recall in which the participants were asked to record the activity performed most during respective 15-minute time blocks throughout the day and then to rate the relative intensity for each activity.

High caloric intake, underreporting of amounts

In the first part of the study, the mean energy intake from the fast food meal was extremely high (1652 kcal), accounting for 61.6% of estimated daily energy requirements. The researchers also found that overweight teens ate more than lean teens (1860 kcal and 1458 kcal, respectively), whether energy was expressed in absolute terms or relative to estimated daily energy requirements.

In the second part of the study, overweight participants consumed significantly more total energy on fast food days than non-fast-food days (2703 vs. 2295 kcal/day). This pattern was not seen among the lean adolescents, who consumed 2575 kcal/day on fast-food days and 2622 kcal/day on non-fast-food days. Overweight participants tended to underreport total energy intake when compared with their lean participants.

According to the authors, if one assumes a dietary pattern of 3 meals and 1 or 2 snacks per day, the average meal size to maintain energy balance should not exceed 30% of daily energy requirements, or approximately 790 kcal. In the first part of the study, the participants massively over-ate, consuming an average of 1652 kcal (61.6%) of estimated total energy expenditure while in the food court setting. The lean teens consumed virtually the same amount of calories on both days. This suggested that overweight individuals do not compensate completely for the massive fast food portion sizes served today.