* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download The increasing prevalence of snacking among US children from
Survey
Document related concepts
Gastric bypass surgery wikipedia , lookup
Abdominal obesity wikipedia , lookup
Overeaters Anonymous wikipedia , lookup
Saturated fat and cardiovascular disease wikipedia , lookup
Food studies wikipedia , lookup
Diet-induced obesity model wikipedia , lookup
Food coloring wikipedia , lookup
Human nutrition wikipedia , lookup
Food politics wikipedia , lookup
Obesity and the environment wikipedia , lookup
Transcript
The increasing prevalence of snacking among US children from 1977 to 1996 Lisa Jahns, RD, Anna Maria Siega-Riz, RD, PhD, and Barry M. Popkin, PhD Objectives: To determine snacking trends and changes in nutrient contribution of snacking over time. Study design: Nationally representative data from the 1977-78 Nationwide Food Consumption Survey (NFCS77), 1989-91 Continuing Survey of Food Intake by Individuals (CSFII89), and 1994-96 (CSFII96) were used. The sample consisted of 21,236 individuals aged 2 to 18 years. Methods: For each survey year, mean numbers of snacks consumed, mean grams consumed per snack, and mean energy intake from snacks were computed, as was contribution of snacking to total energy intake and fat intake. Snacking was self-defined, and a snacking occasion consisted of all snack foods consumed during a 15-minute period. Differences in means between age groups and across survey years were compared. Results: The prevalence of snacking increased in all age groups. The average size of snacks and energy per snack remained relatively constant; however, the number of snacking occasions increased significantly, therefore increasing the average daily energy from snacks. Compared with non-snack eating occasions, the nutrient contribution of snacks decreased in calcium density and increased in energy density and proportion of energy from fat. Conclusion: Snacking is extremely prevalent in our society. Healthy snack food choices should be emphasized over high-energy density convenience snacks for children. (J Pediatr 2001;138:493-8) ty of higher energy density foods that may be replacing nutrient-dense foods as culprits in the obesity problem.4-5 Descriptive studies have shown that snacking is currently an important component of the diet of Americans as measured by factors such as the snacking occasions per day and percent of snacks eaten outside the home.6 Bigler-Doughton and Jenkins7 reported that 80% of adolescents consumed snacks, and snacks made substantial contributions to adolescents’ intakes of several key nutrients. Cross et al8 found that <1% of children reported never snacking. We examined trends in snacking behaviors among children aged 2 to 18 years over the past 20 years to show how behaviors have changed and the effects of these changes on nutritional intake of children. CSFII NFCS The rapid increases over the past 3 decades in childhood obesity and related complications have led to increased concern over the diets of American children.1-3 Among school-aged children and adolescents, the proportion From the Department of Nutrition, University of North Carolina at Chapel Hill. Submitted for publication Apr 7, 2000; revision received Aug 21, 2000; accepted Oct 5, 2000. Reprint requests: Barry M. Popkin, PhD, Carolina Population Center, University of North Carolina at Chapel Hill, CB No. 8120 University Sq, 123 W Franklin St, Chapel Hill, NC 27516-3997. Copyright © 2001 by Mosby, Inc. 0022-3476/2001/$35.00 + 0 9/21/112162 doi:10.1067/mpd.2001.112162 classified as overweight has grown from 8% to 14% for children and from 6% to 12% for adolescents between 1976 to 1980 and 1988 to 1994.3 The consequences of childhood overweight include abnormal lipid profiles, type 2 diabetes, and greater risk for adult obesity and its related comorbidities.1 Although major shifts in physical activity patterns are associated with the increase in obesity, shifts in dietary pattern might also influence this outcome. Public health researchers have pointed to shifts in dietary behaviors such as “supersizing” of the portions available in many restaurants and fast food outlets, the rapid increase in soft drink consumption, and increased availabili- Continuing Survey of Food Intake by Individuals Nationwide Food Consumption Survey METHODS Survey Design and Sample This study uses data on subjects aged 2 to 18 years from 3 nationally representative surveys of the US population. Of these 21,236 individuals, 12,231 participated in the 1977-78 Nationwide Food Consumption Survey (NFCS77), 4008 participated in the 1989-91 Continuing Survey of Food Intake by Individuals, and 4997 participated in the 1994-96 CSFII96. The United States Department of Agriculture surveys from 1977 and 1989 contain stratified area probability samples of noninstitutionalized US households 493 JAHNS, SIEGA-RIZ, AND POPKIN THE JOURNAL OF PEDIATRICS APRIL 2001 Table I. Proportion of snackers by sociodemographic characteristic in the continuing survey of food intake by individuals, 1994-96 Percent who snack* Sociodemographic characteristics Ages 2-5 y (n = 2183) Ages 6-11 y (n = 1492) Ages 12-18 y (n = 1322) 94.3 93.4 94.9 90.2 93.9 91.5 96.6 91.7 96.9 92.6 90.0 94.4 86.2 82.6 86.9 95.7 88.0 94.7 88.4 86.6 89.9 78.8 85.8 83.7 91.5 84.9 91.0 Male (n = 2511) Female (n = 2486) Non-Hispanic white (n = 3424) Non-Hispanic black (n = 760) Hispanic (n = 813) <185% of national poverty level (n = 2232) >350% of national poverty level (n = 1291) Mother’s education less than or equal to high school diploma (n = 2648) Mother’s education more than high school diploma (n = 2392) *Data are weighted to account for survey design effects and to be nationally representative. Table II. Mean number of snacks per day, grams consumed per snack, kilocalories consumed per snack, and kilocalories obtained per day from snacks by US children from the 1977, 1989, and 1996 CSFII surveys by age group Ages 2-5 y Snacks/day Grams/snack Kilocalories/snack Kilocalories from snacks Ages 6-11 y Ages 12-18 y 1977 1989 1996 1977 1989 1996 1977 1989 1996 1.73 158 171 283 1.87 167 187 331* 2.29*† 153 175 378*† 1.56 200 231 347 1.59 205 250 387 1.99*† 195 243 462*† 1.60 275 296 460 1.62 298* 320 496 1.97*† 307 318 612*† *Data point is significantly different from 1977 data point at the 0.01 level. †Data point is significantly different from 1989 data point at the 0.01 level. in the 48 contiguous states and in all 50 states from 1994 to 1996. These surveys were self-weighting, multistage, stratified area samples of the US population. Detailed information on the methodology pertaining to each survey has been published previously.9-12 Dietary Data The NFCS77 and CSFII89 surveys collected 1 day of intake by in-home, interviewer-administered, 24-hour recall and 2 additional days of selfadministered 1-day food records. The CSFII96 collected 2 nonconsecutive, interviewer-administered, 24-hour recalls. For children <12 years, information was obtained from the child’s caregiver. For our purpose of studying snacking behavior over time, all the days of dietary intake have been included in this analysis. 494 Definition of a “Snack” For each food item reported, the respondent (or proxy) was asked “About what time did you begin to eat (drink) the (food item)?” Next, the respondent was handed a card on which were printed various eating occasions (ie, breakfast, lunch, dinner, snack). The respondent was then asked “Looking at this card, please tell me what you would call this occasion?” This was repeated for each food item reported (the previous questions are verbatim from CSFII96; however, NFCS77 and CSFII89 asked similar questions). Therefore our data contain each food item a person consumed, along with the self-reported eating occasion and beginning eating time for each food item. Because people often consume more than one food item when having a “snack,” we chose not to consider each self-reported snack food item as a separate snack. We arbitrarily grouped the snack food items that had a beginning eating time within 15 minutes of the first snack food item reported as a discrete snack. Once foods were categorized by eating occasion (snacks vs non-snack meals), the gram weight of each snack and nutrients contributed by snacks and non-snacks (meals) was computed for each survey year by age group. Statistical Analysis For each survey year, the percentage of individuals who consumed at least one snack on the days covered was determined. Then for snackers, the mean numbers of snacks consumed, mean grams consumed per snack, and mean energy intake from snacks were computed for each survey year. The contribution of snacking to total energy in- JAHNS, SIEGA-RIZ, AND POPKIN THE JOURNAL OF PEDIATRICS VOLUME 138, NUMBER 4 take and total fat intake was also estimated. To examine differences of snacking behaviors by age, individuals were stratified into 3 age groups; 2 to 5 years old, 6 to 11 years old, and 12 to 18 years old. The proportion of snackers by key sociodemographic groups was compared in the 1996 survey. Differences testing used SAS version 6.12 (SAS Institute, Cary, NC) and SUDAAN 7.51 (Research Triangle Institute, Research Triangle Park, NC) statistical software packages to weight the results and control standard errors for sample design effects. A P value <.01 was used to denote statistical significance. Fig 1. Percent of children consuming snacks by age group from the CSFII in 1977, 1989, and 1996. Solid bars, 1977; open bars, 1989; hatched bars, 1996. RESULTS Who Is Snacking? The prevalence of snackers among children increased over all ages from 77% to 91% during the years covered. The changes in the percent of snackers, overall and within age groups, were minimal or nonexistent between 1977 and 1989; most of the increase occurred between 1989 and 1996 (Fig 1). The percent of children consuming snacks by sociodemographic characteristics in 1996 is shown in Table I. For each sociodemographic characteristic except Hispanic ethnicity, the oldest children had the lowest proportion of snackers. Slightly more boys than girls snacked, and a greater proportion of Hispanic and white children snacked than black children in all age groups. A higher proportion of snackers was found at the higher income and education levels than at the lower levels. Behavioral Changes in Snacking Habits The most significant change in snacking behavior was the greater number of snacking occasions per day, not in the amount of energy consumed per snack. Contribution of daily calories by snacks increased by 30% between 1977 and 1996, with large changes occurring both between 1977 and 1989 and between 1989 and 1996 Fig 2. Contribution of snacking to total daily energy intake by year and age group for participants in the CSFII surveys. Number above bar represents total caloric intake. Hatched bars, Energy from meals; solid bars, energy from snacks. (Table II). The mean number of snacks per day increased by 24% to 32% (approximately 0.4 snacking events per day) depending on age group, with the major change occurring in the 1989 to 1996 period. Overall, the energy per snack increased only 3%, and the quantity in grams increased only 1%. Nutritional Impact of Shifts in Snacking Behavior The contribution of non-snack meals and snacks to total daily energy intake is shown in Fig 2. The total energy intake overall and within each age group increased from 1977 to 1996. Overall, snacks contributed approximately one fifth of energy intake in 1977, increasing to approximately one fourth of energy intake by 1996. The 1989 percent energy from snacks values fell midway between the 1977 and 1996 values in all age groups. In every period examined, the 12- to 18-year olds derived the highest proportion of calories from snacks. Although total average fat intake de495 JAHNS, SIEGA-RIZ, AND POPKIN THE JOURNAL OF PEDIATRICS APRIL 2001 Table III. Key nutrient density of snacks and meals of US children in the CSFII 1977, 1989, and 1996 surveys by age group Calcium (mg/1000 kcal) Age 2-5 y 1977 snack 1989 snack 1996 snack 1977 meal 1989 meal 1996 meal Age 6-11 y 1977 snack 1989 snack 1996 snack 1977 meal 1989 meal 1996 meal Age 12-18 y 1977 snack 1989 snack 1996 snack 1977 meal 1989 meal 1996 meal Fiber g/1000 kcal Folate (µg/1000 kcal) 557.0 (16.5) 500.0 (20.9) 488.9 (11.0)* 558.5 (6.4) 587.5 (12.5) 543.2 (5.0)† 6.8 (0.21) 6.5 (0.42) 7.7 (0.21)*† 6.5 (0.06) 6.9 (0.13)* 7.0 (0.07)* 94.5 (3.03) 103.6 (7.57) 101.6 (2.92) 152.8 (1.52) 162.2 (4.56) 154.0 (1.75) 503.7(11.2) 425.0 (19.4)* 399.8 (11.9)* 536.0 (4.0) 533.4 (8.8) 511.0 (7.1)* 7.2 (0.19) 7.0 (0.4) 7.1 (0.21) 6.7 (0.06) 7.0 (0.12) 7.0 (0.11) 90.4 (2.73) 99.2 (7.41) 94.7 (3.82) 148.0 (1.36) 153.8 (3.19) 146.3 (2.39) 476.3 (8.6) 457.2 (31.3) 380.1 (12.8)* 483.9 (4.6) 470.3 (10.2) 433.0 (5.7)*† 6.2 (0.15) 6.1 (0.25) 6.6 (0.25) 6.5 (0.07) 6.8 (0.14) 6.7 (0.09) 93.5 (3.14) 98.6 (8.49) 95.1 (5.49) 135.0 (1.37) 141.4 (3.34) 127.6 (2.87)† *Data point is significantly different from 1977 data point at the 0.01 level. †Data point is significantly different from 1989 data point at the 0.01 level. creased for all age groups between 1977 and 1996 (there were small increases from 1989 to 1996 among 2- to 5-year-olds and 12- to 18-year-olds), the absolute and relative proportions of fat from snacks show an increasing trend over the periods covered (Fig 3). The largest increase in the proportion of fat consumed as a snack occurred among the 2 younger age groups, with a smaller but statistically significant increase among 12- to 18-year-olds. Micronutrient Contribution of Snacks Compared with Meals Table III presents mean nutrient intake from snacks and meals in each survey year by age group. Regardless of age, snacks were more energy dense than meals, and the energy density of snacks increased significantly over time, whereas for meals it remained stable (Table III). The increase in the 496 energy density of snacks over all age groups was 0.14, equal to 0.2 kcal/g of food. Fat density of meals decreased significantly for all age groups, whereas the fat density of snacks did not change for 2- to 5-year-olds or 6- to 11year-olds. Calcium is of concern because of the rapid displacement of milk with sweetened beverages.13 These data indicate a decline in calcium density in snacks and meals during the past 20 years for all age groups. This decline is greater in magnitude in snacks than in meals. Iron density has increased significantly in both snacks and meals for all age groups, although snacks are still less iron-dense than meals. Although zinc density of snacks is only approximately half that of meals, there has been a decrease in zinc density in meals for all age groups. However, among 2- to 5-year-olds, the zinc density of snacks increased. Fiber increased in meals while remaining fairly stable in snacks throughout the years. Folate density of snacks and meals increased in 1989 but then declined in 1996. Several other nutrients were examined but not reported. Sodium and niacin increased in snacks for all age groups over time. Also, thiamin and polyunsaturated fat increased in snacks eaten by 2- to 5-year-olds and 6- to 11-year-olds, whereas vitamin B6 remained stable in snacks eaten by 6to 11-year-olds. Vitamin C and monounsaturated fats also increased in snacks eaten by 2- to 5-year-olds. Saturated fat, cholesterol, B12, riboflavin, and phosphorus declined in all age groups’ snacks, whereas protein, magnesium, and potassium decreased in snacks consumed by 6- to 11-yearolds. For all age groups, there was no change in vitamin A, vitamin E, carotene, or copper obtained from snacks. DISCUSSION This study presents a picture of an important increase in the prevalence and dietary contribution of snacking in the diets of US children. Currently, snacking represents approximately a fourth of the energy and a fifth of many other nutrients, similar to any other meal occasion. The increase in nutrient contribution is primarily caused by an increase in the frequency of snacking and not the size of each snack. Moreover, energy density is much higher for snacks than the non-snacking component of the diet, a component that has increased dramatically between 1977 and 1996 (approximately .14 to .20 kcal/g more). Given the public health concern of increasing child obesity rates, there are several interesting issues raised by this analysis. Supersizing of portions is raised as one of the causes of the excess dietary intake of the American public. These data showed no significant JAHNS, SIEGA-RIZ, AND POPKIN THE JOURNAL OF PEDIATRICS VOLUME 138, NUMBER 4 changes in the reported size of snacks consumed over the last 20 years. In fact, the size of the average snack consumed remained almost constant between 1977 and 1996. What does emerge as a potential contributor is the increased energy density of snacks amid a constant energy density of meals. Energy density is a critical element in overconsumption.14-16 Some link increased energy density with less satiety per gram of food intake and hence with passive overconsumption and increased obesity.15-17 The potential limitations of this study include bias in unknown directions by changes in survey methods throughout the periods surveyed. The nonlinearity of the decrease in fat intake shown in Fig 3 may be an artifact of improved probing methods, as may be the increase in the number of snacks. However, no studies have explored the effect of these methodologic changes on nutrient estimates in the CSFII surveys. In addition to changes in survey methodology, real changes in the food supply occur, and therefore the composition of the nutrient databases is critical for detecting changes. Each survey used its own United States Department of Agriculture nutrient database. However, we have created a way to link food codes from previous surveys and then apply values from the 1994 United States Dietary Association nutrient database to the 1977 and 1989 surveys. The 1994-96 survey uses an updated database for each year of collection (1994, 1995, and 1996), but we believe that fewer changes occurred between 1994 and 1996 than between 1977 and 1996. Real changes in the food supply will not be captured by this method, and trends may be over- or underestimated. In weighing the advantages and disadvantages of using different nutrient databases, we concluded that using the 1994 nutrient data provides a conservative measure of some of the nutrient trends in food (eg, fat) and allows for the examination of trends in several Fig 3. Contribution of snacking to total daily fat intake by year and age group for participants in CSFII surveys. Number above bar represents total fat intake (in grams). Hatched bars, Fat from meals; solid bars, fat from snacks. nutrients (eg, fiber) that would not have been possible otherwise. Another issue pertains to the number of days of data collection. In the first 2 surveys, 3 days of data were used to identify snackers, whereas in 1994-96 only 2 days were used. In 1977 and 1989 only approximately 4% of the subjects snacked only on the third day of data collection. It was our decision to err on the conservative side and include all days of intake. Our measurement of a snacking occasion is a more conservative one than others have used. In this study all self-defined snack foods consumed within a 15-minute span were grouped to represent one snacking occasion, whereas other researchers have counted each snack food eaten at a unique time interval as a snacking occasion.6,7 There is also a difference in how snacks are defined. Time of day, type of food, and foods not linked with a meal have been used to define a snack.8,18-21 To date, there is no consensus in the literature as to how to define what constitutes a meal or a snack. It is clear that there is an increase in the role of snacking and a strong possi- bility that snacking has contributed to the epidemic of obesity in US children. Longitudinal studies are required to examine this potential pathway. Meanwhile, there is a need in the food supply for less energy dense and more healthful snacks that are appealing to children. REFERENCES 1. Pinhas-Hamiel O, Dolan LM, Daniels SR, Standiford D, Khoury PR, Zeitler P. Increased incidence of non-insulindependent diabetes mellitus among adolescents. J Pediatr 1996;128:608-15. 2. Troiano RP, Flegal KM. Overweight children and adolescents: description, epidemiology, and demographics. Pediatrics 1998;101:497-504. 3. U.S. Department of Health and Human Services. Update: Prevalence of overweight among children, adolescents, and adults—United States 198894. MMWR Morb Mortal Wkly Rep 1997;46:199-202. 4. Harnack L, Stang J, Story M. Soft drink consumption among US children and adolescents: nutritional consequences. J Am Diet Assoc 1999;4:436-41. 5. Jacobsen M, Nestle M. Halting the obesity epidemic: a public health poli497 JAHNS, SIEGA-RIZ, AND POPKIN 6. 7. 8. 9. 10. cy approach. Public Health Rep 2000;115:12-24. Frazao E, editor. American’s eating habits: changes and consequences. Washington (DC): US Department of Agriculture Information Bulletin Number 750; 1999. p. 1-473. Bigler-Doughton S, Jenkins R. Adolescent snacks: nutrient density and nutritional contribution to total intake. J Am Diet Assoc 1987;87:1678-9. Cross A, Babicz D, Cushman LF. Snacking patterns among 1,800 adults and children. J Am Diet Assoc 1994; 94:1398-403. Rizek RL. The 1977-78 nationwide food consumption survey. Fam Econ Rev 1978;4:3-7. Tippett KS, Mickle SJ, Goldman JD, Sykes KE, Cook DA, Sebastian RS, et al. Food and nutrient intakes by individuals in the United States, 1 day, 1989-91. Continuing survey of food intakes by individuals 1989-91, Nationwide Food Surveys Rep. No 91-2. U.S. Department of Agriculture, Agriculture Research Service, 1995. THE JOURNAL OF PEDIATRICS APRIL 2001 11. Tippett KS, Cypel YS. Design and operation: the continuing survey of food intakes by individuals and the diet and health knowledge survey 1994-96. Continuing survey of food intakes by individuals 1994-96, Nationwide Food Surveys Rep. 96-1. U.S. Department of Agriculture, Agriculture Research Service, 1997. 12. Siega-Riz AM, Popkin BM, Carson T. Trends in breakfast consumption for children in the united states from 1965 to 1991. Am J Clin Nutr 1998;67 (suppl):748s-56s. 13. Cavadini C, Siega-Riz AM, Popkin BM. US adolescent’s food intake trends from 1965-1996. Arch Dis Child 2000;83:18-24. 14. Bray GA, Popkin BM. Dietary fat intake does affect obesity! Am J Clin Nutr 1998;68:1157-73. 15. Drewnowski A. Energy density, palatability, and satiety: implications for weight control. Nutr Rev 1998;56: 347-53. 16. Rolls BJ, Kim-Harris S, Fischman 17. 18. 19. 20. 21. MW, Foltin RW, Moran TH, Stoner SA. Satiety after preloads with different amounts of fat and carbohydrate: implications for obesity. Am J Clin Nutr 1994;60:476-87. Blundell JE, Macdiarmid JI. Passive overconsumption. Fat intake and short-term energy balance. Ann NY Acad Sci 1997;827:392-407. Devaney BL, Gordon AR, Burghardt JA. Dietary intakes of students. Am J Clin Nutr 1995;61(suppl):205S-12S. Ezell JM, Skinner JD, Penfield MP. Appalachian adolescents’ snack patterns: morning, afternoon, and evening snacks. J Am Diet Assoc 1985;85: 1450-4. McCoy H, Moak S, Kenney MA, Kirby A, Chopin L, Billon W. Snacking patterns and nutrient density of snacks consumed by southern girls. J Nutr Epidemiol 1986;18:61-6. Summerbell CD, Moody RC, Shanks J, Stock MJ, Geissler C. Sources of energy from meals versus snacks in 220 people in four age groups. Eur J Clin Nutr 1995;49:33-41. Receive tables of contents by e-mail To receive the tables of contents by e-mail, sign up through our Web site at http://www.mosby.com/jpeds Choose E-mail Notification. Simply type your e-mail address in the box and click the Subscribe button. Alternatively, you may send an e-mail message to [email protected]. Leave the subject line blank and type the following as the body of your message: subscribe jpeds_toc You will receive an e-mail to confirm that you have been added to the mailing list. Note that table of contents e-mails will be sent out when a new issue is posted to the Web site. 498