Adolescents overeat fast food, but lean adolescents compensate for over-consumption by eating less later

Adolescents are more likely to overeat when served fast food, but lean adolescents tend to compensate for the over-consumption by eating less at other meals, which is not something their overweight counterparts are likely to do, according to a study in the June 16 issue of the Journal of the American Medical Association (JAMA).

"Consumption of fast food has increased rapidly since the 1970s among adolescents from all socioeconomic and racial/ethnic groups across the United States," the authors provide as background information in the article. "An estimated 75 percent of adolescents eat fast food one or more times per week. The increase in fast food consumption parallels the escalating obesity epidemic, raising the possibility that these 2 trends are causally related," the authors suggest. "Characteristics of fast food previously linked to excess energy intake [overeating] or adiposity [fat] include enormous portion size, high energy density, palatability, excessive amounts of refined starch and added sugars, high fat content, and low levels of dietary fiber."

In this study, Cara B. Ebbeling, Ph.D., from Children's Hospital, Boston, and colleagues conducted two studies to evaluate the effects of fast food on energy intake in overweight versus lean adolescents. Fifty-four adolescents were enrolled in the studies (26 overweight, 28 lean) aged 13 to 17 years who reported eating fast food at least one time per week. Fifty-one (24 overweight, 27 lean) of the 54 participants enrolled in study 1 also completed study 2. In this investigation, the researchers grouped adolescents who were overweight and at risk of overweight into one group and adolescents with a BMI [body mass index = weight in kilograms divided by the square of height in meters] not exceeding the 85th percentiles for their ages were considered lean.

In study one, participants were fed extra large fast food meals in a food court and instructed to eat as much or as little as desired during the one-hour meal. In study two, the researchers assessed how much food was eaten under free-living conditions for two days when fast food was consumed and two days when it was not consumed. The participants recalled dietary and physical activity on telephone interviews. Data were collected between July 2002 and March 2003.

"In study 1, mean [average] energy intake from the fast food meal among all participants was extremely large (1,652 kcal =calories), accounting for 61.6 percent of estimated daily energy requirements," the researchers found. "Overweight participants ate more than lean participants whether energy was expressed in absolute terms (1,860 vs. 1,458 kcal) or relative to estimated daily energy requirements (66.5 percent vs. 57 percent). In study 2, overweight participants consumed significantly more total energy on fast food days than non-fast food days (2,703 vs. 2,295 kcal/d; plus 409 kcal/d), an effect that was not observed among lean participants (2,575 vs. 2,622 kcal/d; less 47 kcal/d)." The researchers also found that overweight participants tended to under-report total energy intake compared with lean participants.

"...the overweight participants consumed more total energy on days with than without fast food, in contrast to the lean participants, who consumed virtually the same amount on both days. This observation suggests that overweight individuals do not compensate completely for the massive portion sizes characteristic of fast food today," the author note. "… these findings suggest that, at least, fast food consumption serves to maintain or exacerbate obesity in susceptible individuals."

"In this study, adolescents overconsumed fast food regardless of body weight, although this phenomenon was especially pronounced in overweight participants. Moreover, overweight adolescents were less likely to compensate for the energy in fast food, by adjusting energy intake throughout the day, than their lean counterparts," the authors conclude.

JAMA: The Journal of the American Medical Association