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* US Department of Agriculture, Agricultural Research Service, Beltsville, Maryland
Department of Society, Human Development, and Health, Harvard School of Public Health, Boston, Massachusetts
Department of Medicine, Children’s Hospital, and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts
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ABSTRACT |
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 TOP ABSTRACT METHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Methods. This study included 6212 children and adolescents 4 to 19 years old in the United States participating in the nationally representative Continuing Survey of Food Intake by Individuals conducted from 1994 to 1996 and the Supplemental Children’s Survey conducted in 1998. We examined the associations between fast-food consumption and measures of dietary quality using between-subject comparisons involving the whole cohort and within-subject comparisons involving 2080 individuals who ate fast food on one but not both survey days.
Results. On a typical day, 30.3% of the total sample reported consuming fast food. Fast-food consumption was highly prevalent in both genders, all racial/ethnic groups, and all regions of the country. Controlling for socioeconomic and demographic variables, increased fast-food consumption was independently associated with male gender, older age, higher household incomes, non-Hispanic black race/ethnicity, and residing in the South. Children who ate fast food, compared with those who did not, consumed more total energy (187 kcal; 95% confidence interval [CI]: 109–265), more energy per gram of food (0.29 kcal/g; 95% CI: 0.25–0.33), more total fat (9 g; 95% CI: 5.0–13.0), more total carbohydrate (24 g; 95% CI: 12.6–35.4), more added sugars (26 g; 95% CI: 18.2–34.6), more sugar-sweetened beverages (228 g; 95% CI: 184–272), less fiber (–1.1 g; 95% CI: –1.8 to –0.4), less milk (–65 g; 95% CI: –95 to –30), and fewer fruits and nonstarchy vegetables (–45 g; 95% CI: -58.6 to –31.4). Very similar results were observed by using within-subject analyses in which subjects served as their own controls: that is, children ate more total energy and had poorer diet quality on days with, compared with without, fast food.
Conclusion. Consumption of fast food among children in the United States seems to have an adverse effect on dietary quality in ways that plausibly could increase risk for obesity.
Key Words: fast food • obesity • dietary composition • diet quality • energy intake
Abbreviations: CSFII, US Department of Agriculture’s Continuing Survey of Food Intakes by Individuals • BMI, body mass index • MSA, metropolitan statistical area
From its origins in the 1950s, fast food has grown into a dominant dietary pattern among children in the United States today.1,2 Consumption of fast food by children increased a remarkable fivefold from 2% of total energy in the late 1970s to 10% of total energy in the mid-1990s.3 The number of fast-food restaurants more than doubled from 1972 to 1995 and now totals an estimated 247 115 nationwide.4 Fast food pervades virtually all segments of society including local communities, public schools, and hospitals.5–7 These trends seem to have been driven by massive advertising and marketing campaigns aimed at children and their parents.2
Several dietary factors inherent to fast food may cause excessive weight gain such as massive portion size, high energy density, palatability (appealing to primordial taste preferences for fats, sugar, and salt), high content of saturated and trans fat, high glycemic load, and low content of fiber.8 However, few studies have examined the effects of fast-food consumption in children.9–11 In the absence of such data, professional nutritional agencies in the United States12 presently support industry claims that fast food can be part of a healthful diet.13,14
The aims of this study were first to examine national patterns of fast-food consumption among children and second to determine whether fast food adversely affects diet quality in ways that might plausibly increase risk for obesity.
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METHODS |
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Design
In these nationally representative household population surveys, the primary hypothesis was that subjects who consumed food obtained at fast-food restaurants, compared with those who did not, would exhibit higher total energy intake and poorer diet quality over the day studied. Multiple regression was used to control for potentially confounding demographic, socioeconomic, and anthropometric covariates. We also conducted within-subject comparisons on a subset of individuals who were discordant in fast-food consumption on the 2 survey days, because such models control for between-subject confounding variables.
Assessment of Diet and Other Variables
CSFII 1994 to 1996 and CSFII 1998 collected dietary intake data on 2 nonconsecutive days, 3 to 10 days apart. For between-subject comparisons, we used data from the first survey day because of the higher overall response rate (for all participants including children and adults, the response rate in CSFII 1994 to 1996 was 80.0% on day 1 compared with 76.1% on day 2; and in CSFII 1998, the response rate was 85.6% on day 1 compared with 81.7% on day 2). Dietary data were obtained through an interviewer-administered 24-hour recall by using a multiple-pass technique to reduce under-reporting. Survey instruments were tested in a pilot study, and, based on the study results, the instruments were revised appropriately. Food coders, field supervisors, and interviewers were trained before the survey.16 Measuring guides were used to help respondents estimate the amount of food and beverages consumed. Spanish-language questionnaires were used when appropriate. The accuracy and utility of translations were checked before the survey. If a sampled person spoke neither English nor Spanish, a family member or neighbor 
16 years old served as an interpreter.
In the surveys, children 12 years old provided information on their dietary intakes. Children 6 to 11 years old were asked to describe their own food intakes and were assisted by an adult household member (proxy) who was responsible for preparing the child’s meals. Proxy interviews were conducted for children <6 years old and any sampled person who could not report for themselves because of physical or mental limitations. Information on height and weight was obtained from the sampled persons or their proxy person. Body mass index (BMI) was calculated by dividing weight by height-squared and expressed as kg/m2.
The surveys sought information as to where each food or beverage was obtained and included: stores such as supermarkets, farmer’s markets, commissaries, or specialty stores; restaurants; bars, taverns, or lounges; fast-food or pizza places; vending machines; school cafeterias; soup kitchens; meals on wheels; child care or adult day care centers; and food grown or caught by the respondents or someone known to the respondent. In this study, foods obtained at fast-food and pizza places were grouped collectively as obtained from fast-food places.
We used nutrients and food groups as defined in the CSFII 1994 to 1996.17 Food amounts were determined from the weight in grams of foods and beverages in the form reported consumed (including water present in beverages such as tea, coffee, fruit drinks made from dry mixes, cocoa, and milk drinks; excluding water drunk separately such as tap and bottled water). Energy density was determined as total energy intake in kilocalories divided by total weight in grams, excluding beverages.
At the screening interview, conducted to determine whether any household member was eligible to participate, information was collected on the number of people living in a household, their names, date of birth, age, sex, race, ethnicity, and household income.
The 4 geographic regions (Northeast, Midwest, South, and West) in the CSFII are as defined by the US Department of Commerce for the 1990 census population. A metropolitan statistical area (MSA) is a geographic area consisting of a large population nucleus together with adjacent communities that have a high degree of economic and social integration with the nucleus, according to the Office of Management and Budget.
Statistical Analyses
For between-subject comparisons, we calculated mean food and nutrient intakes of those who ate fast food and those who did not eat fast food on the first survey day. In addition, we estimated independent associations between fast food and measures of diet quality by using multiple regression. In the baseline model, fast-food consumption status, age, and gender were the independent variables. In a second model, race/ethnicity, household income groups, urbanization, and geographic region were added to the baseline model. A third model included BMI with the independent variables in the second model. Of 6212 children in the study, 832 had no BMI values and therefore were excluded from the third regression model. Because of the large amount of missing data and concerns about the validity of youth and parent reports of weights and heights, BMI was used as a covariate in some analyses and not as a primary analysis variable.
For within-subject comparisons, we calculated mean food and nutrient intakes of 2080 children discordant in fast-food consumption on the 2 survey days, comparing the day that fast food was eaten with the day that fast food was not eaten. We adjusted the difference in consumption levels between days for age, gender, race/ethnicity, household income groups, urbanization, geographic region, and order effect (whether fast food was eaten on survey day 1 or 2).
The SUDAAN software package (SAS-Callable Mainframe SUDAAN for Solaris, release 8.0.1, Research Triangle Institute, Research Triangle Park, NC) was used for regression analysis and for the estimation of percentages, means, standard errors of the means, and pairwise comparisons (P < .05) among groups. SAS was used only for variable selection, variable manipulation, and running SAS callable-SUDAAN (SAS for SunOS, release 8.2, 1999–2001, Cary, NC). All the surveys used a complex, multistage probability sampling design to provide representative samples of noninstitutionalized children and adolescents in the United States. Estimates in this study are based on weighted observations and reflect the probability of selection, nonresponse, and poststratification adjustments. Detailed descriptions of the samples have been published elsewhere.16,17 All P values are 2-tailed.
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RESULTS |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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15% among children who were fast-food consumers.
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DISCUSSION |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Because 30.3% of study participants ate fast food on any given day, these foods seem to contribute an additional 57 kcal (187 kcal x 30.3%) to the daily diet of the average child in the United States. This energy increment theoretically could account for an additional 6 pounds of weight gain per child per year, assuming 3500 kcal/pound of body weight, if energy expenditure were unchanged. Preliminary findings from a prospective study of 5114 young adults support this possibility. The odds of becoming obese over a 15-year period increased by 86% among young white adults (but not among blacks) visiting fast-food restaurants more than twice per week, compared with those visiting fast-food restaurants less than once per week, after adjustment for potential confounders.20
Several factors inherent to fast food may increase energy intake, thus promoting a positive energy balance and increasing risk for obesity. Children and adolescents who ate fast food on a typical day, compared with those who did not, consumed more total and saturated fat, more total carbohydrate and added sugars, less dietary fiber, and more energy per gram of solid food (ie, higher nonbeverage energy density). This profile reflects the composition of typical fast-food fare (cheeseburgers, french-fried potatoes, sugar-sweetened beverages, etc) popular among youth.21 The high energy density and palatability of fat may promote excess energy intake,22 and total dietary fat has been directly associated with adiposity in some23,24 but not all25,26 studies. Because fast-food meals are high in refined starch and added sugars, they have a high glycemic index and glycemic load.27 High glycemic load meals seem to elicit a sequence of physiologic events that promote energy intake in the short term,28 although the relevance of glycemic index and glycemic load in the long-term control of body weight is a subject of debate.29,30 Dietary fiber promotes satiation and satiety31 and may protect against excessive weight gain via effects that could be mediated by and/or independent of glycemic index.32 Furthermore, fast food is served in increasingly large portion sizes.33 Portion size has been linked to voluntary energy intake in several recent studies.34,35
Fast food may also compromise diet quality in ways that might affect body weight by displacing more healthful food options. Children who ate fast food, compared with those who did not, consumed more sugar-sweetened beverages, less milk, and fewer fruits and nonstarchy vegetables. Prospective studies indicate a positive association for sugar-sweetened soft drinks36 and an inverse association for milk37 with the odds for becoming obese in children or young adults. Fruits and nonstarchy vegetables may protect against excessive weight gain because of their low energy density, high fiber content, and low glycemic index. Moreover, inadequate consumption of fruits and vegetables has been associated with obesity-related morbidities such as cardiovascular disease38,39 and diabetes.40
The food and nutrient profiles of subjects who ate fast food closely reflect dietary patterns among children who infrequently eat dinner with their families.41 These children consume fewer fruits and vegetables, more fried food and soda, more saturated and trans fat, higher glycemic load, and less fiber and micronutrients. In a hectic society, busy family routines foster a need for quick and convenient meals42 and may preclude preparation of healthful dinners at home. Adolescents are, in fact, obtaining an increasing proportion of their total energy intake away from home, often at fast-food establishments.43
Although there were some differences in fast-food consumption among socioeconomic and demographic groups, the prevalence among any of these groups was >23% on a typical day. From a sociocultural perspective, the ubiquity of fast-food establishments may account for this high level of consumption. One especially relevant trend is the increasing availability of fast food in school cafeterias.2,6 In an ecological study of 23 middle schools in San Diego, CA, a la carte sales of brand name and school-prepared fast food exceeded 15 000 items per week.5 Of particular interest, school socioeconomic status was directly related to the total number of a la carte sales, of which 27% were for fast food. Despite the ubiquity of fast food, children of higher socioeconomic status may have more discretionary money and consequently greater access to fast food, and this fact may account for the independent relationship of higher income to greater consumption of fast food in our study.
The observed direct association of fast-food consumption with age is not surprising. Adolescence represents a time of increasing autonomy, and teenagers purchase more fast food with their own money than younger consumers.2 The workforce at fast-food restaurants is largely comprised of adolescents1 who may receive discounted or free food as part of their compensation.9 Moreover, youth may be progressively influenced over time by pervasive advertising because of the cumulative effects of repetitious messages. The industry markets heavily to children with the goal of fostering a fast-food habit that will persist into adulthood.44
One methodological issue should be noted. The study relies on self-report of intake (assisted by adult household members of young children), a dietary assessment technique that may be inaccurate and imprecise. However, the 24-hour recall methodology used here arguably provides valid estimates of dietary intake on a group level in children.45,46 When recall methodology was compared with total energy expenditure using the doubly labeled water technique, nearly 80% of children were classified as "accurate" or "over" reporters.47 Given the escalating obesity epidemic, it is possible that some of the over reporters were accurately recalling dietary intake but eating in excess of total energy expenditure.
Our results are largely consistent with those of previous studies. French et al9 found fast-food consumption to be associated with higher total energy intake and poorer diet quality among adolescents in a metropolitan area of Minnesota. McNutt et al10 found that adolescent girls who ate fast food >4 times per week consumed more total energy than those who ate fast food less frequently. Cusatis and Shannon11 observed that fast-food consumption was a significant predictor of dietary fat among girls but not boys.
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CONCLUSIONS |
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Reprint requests to (D.S.L.) Department of Medicine, Children’s Hospital, 300 Longwood Ave, Boston, MA 02115. E-mail: david.ludwig{at}childrens.harvard.edu
This work is solely the responsibility of the authors and does not represent official views of the Centers for Disease Control and Prevention.
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