nutrient-poor food on children's food intake and obesity in South Korea

Appetite 81 (2014) 305–311

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Research report

Effects of exposure to television advertising for energy-dense/ nutrient-poor food on children’s food intake and obesity in South Korea ☆ Bora Lee a, Hyogyoo Kim b, Soo-Kyung Lee c, Jihyun Yoon d, Sang-Jin Chung a,* a

Department of Foods and Nutrition, Kookmin University, 77 Jeongneung-ro, Seungbuk-gu, Seoul 136-702, South Korea Department of Advertising and Public Relations, Dongguk University, 30 Pildong-ro 1-gil, Jung-gu, Seoul 100-175, South Korea c Department of Food and Nutrition, Inha University, 100 Inharo, Nam-gu, Incheon 402-751, South Korea d Department of Food and Nutrition, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, South Korea b

A R T I C L E

I N F O

Article history: Received 3 September 2013 Received in revised form 28 May 2014 Accepted 26 June 2014 Available online 1 July 2014 Keywords: TV advertising Energy-dense/nutrient-poor food Food intake Preference Obesity Children

A B S T R A C T

The aim of this study was to determine the effect of television food advertising on participant food intake and risk of obesity. A total of 2419 children aged 11–13 years were selected from 118 elementary schools in South Korea. All participants completed a self-administered questionnaire with questions about height, weight, television viewing times, food preferences, and food intakes. To estimate actual exposure to food advertising, we asked participants to specify the times at which they usually watched television. We then collected data on the various types of food advertisement broadcast on five different television networks during those viewing times over the course of the previous 7 months. The amount of television watched and exposure to energy-dense/nutrient-poor (EDNP) food advertising were associated with an increased risk of being overweight or obese. Exposure to television advertising for EDNP food was also significantly associated with higher EDNP food preference and intake and lower fruit and vegetable intake. However, these relationships disappeared for all foods after adjusting for the overall amount of television watched. Although it was not possible to conclude that exposure to television advertising for EDNP food was associated with an increased risk of obesity, preference for EDNP foods, or overall food intake due to the strong comprehensive effects of television viewing time, there was a reason to believe the evidence of the effects of advertising in this study. Future longitudinal studies are needed to determine the exclusive effects of exposure to television advertising for EDNP food. © 2014 Elsevier Ltd. All rights reserved.

Introduction Television food advertising has been criticized for its potential role in exacerbating the obesity epidemic by promoting unhealthy dietary practices in children (Lobstein & Dibb, 2005; World Health Organization, 2010). In particular, the marketing of energy-dense/ nutrient-poor (EDNP) foods and beverages has become a major area of concern in children’s food advertising. The World Health Organization (WHO) released recommendations for an International Code on Marketing of Foods and Non-Alcoholic Beverages to Children to reduce obesity among children (World Health Organization, 2010). Many studies have also emphasized that governments and industries need to develop clear, achievable statements regarding objec-

☆

Acknowledgements: We gratefully acknowledge research support from the Korean Food and Drug Administration [08082Meokeulgeori999-4105]. * Corresponding author. E-mail address: [email protected] (S.-J. Chung). http://dx.doi.org/10.1016/j.appet.2014.06.103 0195-6663/© 2014 Elsevier Ltd. All rights reserved.

tives and campaigns for statutory restrictions (Hawkes, 2007; Hawkes & Lobstein, 2011). EDNP food advertising targeted toward children and adolescents has been shown to be one of the major environmental influences on food intake among young people (Harris, Bargh, & Brownell, 2009). Cumulative exposure to television food advertising has also been shown to influence attitudes and beliefs toward certain foods in controlled situations (Dixon, Scully, Wakefield, White, & Crawford, 2007). Children and adolescents who reported paying attention to television advertisements were more likely to request and buy advertised snacks relative to those who did not pay attention to television advertising (Borzekowski & Robinson, 2001; Parvanta et al., 2010). In a study examining spot market advertising, which can differentiate individual local advertising exposure in a selected geographic area, a strong association was found between fast food advertising and increased food intake and body mass index (BMI) in overweight and obese children. They concluded that EDNP food advertising may increase the consumption of unhealthy foods (Andreyeva, Kelly, & Harris, 2011; Halford, Gillespie, Brown, Pontin, & Dovey, 2004).

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Despite strong interest in the effect of television food advertising on dietary habits and health, there is a clear lack of evidence directly linking food advertising to food intake or obesity, primarily due to difficulty measuring exposure to television food advertising in a real world setting. Most studies examining the association between food intake and television food advertising have collected data on viewing exposure through the use of surveys that included questions about how often participants watched advertisements (Jordan, Trentacoste, Henderson, Manganello, & Fishbein, 2007) or by showing specific advertisements in simulated settings within a restricted setting or within a short time period (Chernin, 2008). Therefore, study results have not reflected individual differences in natural exposure to television advertising. Other studies have examined the association between food advertisements and obesity or food intake in terms of long-term exposure to advertising in real-world settings. Chou, Rashad, and Grossman (2008) calculated the number of hours that fast-food restaurant advertisements were viewed, using fast-food restaurant television advertising data from tracking services. Results from the study showed a positive association between exposure to fast food advertising and risk of obesity or being overweight in children and adolescents. Zimmerman and Bell (2010) found viewing television commercials to be associated with BMI z scores after adjusting for exercise and eating while watching television. Viewing television without commercials was not associated with BMI z scores, even after adjustment for physical activity. Improved methods of estimating individual exposure to television advertising in real world settings are needed, to determine the associations between television advertisements and obesity and food intake. The detrimental effects of television viewing on obesity have been well documented (Gortmaker et al., 1996); however, it is difficult to determine whether the effect is primarily due to increased food intake (influenced by television food advertising) or a more sedentary lifestyle related to long, inactive periods of television viewing (Hastings et al., 2003). In fact, many studies have examined television viewing as a proxy for exposure to television advertising and reported that television viewing increases one’s exposure to advertisements that promote intake of unhealthy advertised foods (Barr-Anderson, Larson, Nelson, Neumark-Sztainer, & Story, 2009; Cairns, Angus, Hastings, & Caraher, 2013; Council on Communications and Media, 2011; Epstein et al., 2008; Hare-Bruun et al., 2011; Matheson, Killen, Wang, Varady, & Robinson, 2004; Utter, Scragg, & Schaaf, 2006; Wiecha et al., 2006). A study has suggested that food promotion through television advertisements is associated with individual food preferences, and that food advertising may promote strong beliefs and attitudes toward food that is advertised on television (Dixon et al., 2007). Children exposed to food advertising have been shown to be more likely to prefer advertised foods (Borzekowski & Robinson, 2001; Ferguson, Muñoz, & Medrano, 2012; Harris et al., 2009). In addition, exposure to food advertising among children was positively associated with the consumption of advertised food brands and energydense food categories, as well as an increased preference for other food brands in the same product category as the advertised brand (Buijzen, Schuurman, & Bomhof, 2008; Committee on Food Marketing and the Diets of Children and Youth, 2006; Halford, Boyland, Hughes, Oliveira, & Dovey, 2007; Story, 2004). In South Korea, especially among children, the obesity rate has been increasing; in 2010, 8.0% and 10.8% of all children were classified as overweight or obese, respectively (MHWFA & KCDC (Ministry of Health and Welfare and family Affairs & Korea Centers for Disease Control and Prevention), 2011). In response to the large number of fast food and instant noodle advertisements (Han, Powell, & Kim, 2013), the South Korean government enacted The Special Act on Safety Management of Children’s Dietary Life, which outlined guidelines on providing safe food and proper nutrition to

promote health in children. In May 2009, Nutrition Standards for EDNP foods were developed, including restrictions on EDNP food advertising on television, effective from September 2010 (MHWAFA & KFDA (Ministry of Health and Welfare and family Affairs, Korea Food & Drug Administration), 2009). However, due to the lack of research examining the effect of restricting EDNP food advertising on food preference, food intake, and obesity in South Korea, there was considerable resistance from food companies regarding the restrictions set forth by the law. As a result, the legislation was revised under a 3-year sunset provision to restrict advertising of EDNP foods during (a) commercial breaks on children’s television programs; and (b) between 5:00 and 7:00 p.m., which was determined to be the most popular viewing time for children in South Korea. The purpose of our study was to determine the association between exposure to EDNP food advertising in children and food preference, food intake, and obesity, prior to the enactment of the law restricting EDNP food advertising in South Korea. Participants and methods Participants Data were collected during July 2010. Participants were fifthgrade children aged 11–13 years and representative of 118 schools from 16 major cities and provinces throughout South Korea. Stratification was conducted using a variable representing the 16 cities and provinces. Approximately 22 students were selected from one class within each of the schools using cluster random sampling. Of the 118 schools approached to participate in the study, three schools declined the invitation; therefore, three different schools were extracted from the same region. In total, 2517 children were eligible for the study, and of those, 89 were excluded due to inconsistent or improbable questionnaire responses. In total, 2419 participants (1183 boys) were included. All participants completed a selfadministered questionnaire that included questions about height, weight, amount of television watched, food preferences, and food consumption frequency. Informed consent was obtained and the study was approved by the Institutional Review Board of Seoul National University (1006/001–006). Methods Height, weight, and BMI The validity of self-reported height and weight data was confirmed by analyzing information from 422 children. Height and weight were measured using an anthropometer and a scale in centimeters and kilograms, respectively, by nurses from each school. Only 6.9% of children were misclassified when comparing their actual BMI categories to self-reported measures (Lee, Chung, Lee, & Yoon, 2013). Obesity was defined as a BMI ≥95th percentile of the genderspecific BMI for age in the 2007 Korean National Growth Charts, or a BMI of ≥25 kg/m2 (underweight: <5th, normal: ≥5th and <85th, and overweight: ≥85th and <95th). Food preferences and frequency Fruit, vegetables, and 13 EDNP food categories were the food groups used to investigate preferences and intake. EDNP food categories were chosen based on lists of foods banned from being advertised on television by the Korean Food and Drug Administration (KFDA) in May 2010 (KFDA (Korea Food & Drug Administration), 2010). These food lists have been provided monthly since May 2009. The KFDA’s standards for EDNP foods for children are shown for both snacks and meal-type foods in Table 1. Banned food lists from the KFDA were categorized into 13 EDNP food groups based on a set of criteria established in previous studies and food frequency lists used in the Korea National Health and Nutrition Examination Survey

B. Lee et al./Appetite 81 (2014) 305–311

Table 1 Energy-dense/nutrient-poor (EDNP foods defined by the Korean Food and Drug Administration). Definition of EDNP foods in South Korea Food per serving Snack foods for children Meal substitutes for children

1. (250 kcal, >4 g of saturated fats, or >17 g of sugar) & <2 g of protein 2. >500 kcal, >8 g of saturated fatty acid, or >34 g of sugar 1. (>500 kcal or 4 g of saturated fats) & (<9 g of protein or >600 mg of sodium) 2. >1000 kcal or >8 g of saturated fatty acid

(KNHANES) and Korea Youth Risk Behavior Web-Based Survey (KYRBWS); Briefel, Wilson, & Gleason, 2009; MHWFA, KCDC, & MEDST (Ministry of Health and Welfare and Family Affairs, Korea Centers for Disease Control and Prevention & Ministry of Education, Science and Technology), 2008; MHWFA (Ministry of Health, Welfare and Family Affairs), 2009; Phillips et al., 2004; Webb et al., 2006). Food preferences were measured using a numbered ranking system in which 1 = “dislike very much” and 5 = “like very much.” Food intake for the 13 EDNP food categories, fruit, and vegetables were measured using a semi-quantitative food frequency questionnaire (FFQ). The questionnaire was developed using the same format as the food frequency questionnaires used in the KNHANES and KYRBWS (MHWFA, 2009; MHWFA, KCDC, & MEDST, 2008). Portion sizes for foods were represented using pictures, and response categories regarding frequency of food intake were as follows:

• • • • • •

(1) (2) (3) (4) (5) (6)

two or more times a day once a day 4–6 days a week 1–3 days a week 1–3 days a month never

For each food category, the total intake score was calculated from all responses and converted to average frequencies per week:

• • • • • •

1 = 14 2=7 3=5 4=2 5 = 0.5 6=0

EDNP foods used in the analysis included fried snacks, pie snacks (e.g., pies and cookies using pie crust), chocolates, candies and gums, sweet breads (e.g., cakes and doughnuts), ice cream, fruit-flavored juices, soft drinks, non-alcoholic sweetened beverages (e.g., iced tea, shakes, and sport drinks), pizza, hamburgers, fried chicken, and instant noodles (ramen). Television viewing and computer use Study participants were asked when and how often they usually watched television during weekdays and at weekends. Times for television viewing were reported in 1-h intervals (i.e., 4:00–5:00 p.m. and 5:00–6:00 p.m.). The total average number of television hours watched per day was calculated as follows: (hours watched per day on weekdays × number of weekdays watching television) + (hours watched per day on weekends × number of weekend days watching television) / 7 days. Amount of time spent on the computer, including using the Internet and computer programs, playing games, and watching DVDs, was measured from 0 to ≥5 hours per day using hourly intervals.

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Exposure to food advertising Food advertising data from five television networks, four broadcast networks, and one cable network (which were the most viewed by children in South Korea between January 1, 2010 and July 31, 2010), were obtained from advertising agents. Television food advertisements were sorted according to advertising times and food categories (i.e., the 13 EDNP food categories measured in the FFQ and 11 non-EDNP food categories). The advertisements were then sorted according to the time at which study participants usually watched television during weekdays and at weekends, separately, on an hourly basis. Due to difficulty identifying which broadcast channels participants watched during each viewing session and a lack of advertising data for channel variation, we had to assume that participants were exposed to advertising from any one of the five broadcast networks during the viewing times they mentioned on the questionnaires. For example, if participants reported usually watching television from 6:00 to 7:00 p.m., we assumed that they were exposed to all television food advertising broadcast between those hours on any of the five stations. Therefore, levels of exposure to television food advertising were calculated by taking the average total number of food advertisements broadcast on the five network channels, within each of the food categories, during the times that participants reported usually watching television. Total exposure to EDNP food advertising was defined as the sum of all food advertisements per channel (sum of food advertisement/5 channels) for the 13 EDNP food categories during specific viewing time periods. Each EDNP food advertising category and total EDNP food advertising were classified into quartiles based on levels of exposure. Statistics Statistical analysis software SUDAAN 10.0 was used to correct for design effects resulting from clustered sampling while weighing for the South Korean population of fifth-grade children. All data were reported as mean ± standard error (SE) and calculated as a stratified cluster study design in numbers and percentages. The differences and linear trends in food preferences and frequencies of EDNP foods according to exposure to advertisements were analyzed using analysis of variance (ANOVA) and analysis of covariance (ANCOVA). For fruit and vegetable intake, total EDNP food advertising exposure was used instead of individual fruit or vegetable advertisements due to the low frequency of advertising for those foods. The obesity odds ratio of exposure to television food advertising was analyzed using logistic regression. A P-value of ≤0.05 was used to determine statistical significance for linear trends across the quartile of exposure to advertising categories and trends after adjusting for the amount of television watched. Multicollinearity was tested using a variance inflation factor (VIF) to determine whether our model should include a variable representing the amount of television watched. Thereafter, the model including the amount of television watched was also tested, as VIF was 3.75– 3.80, which was under the threshold of 10 (O’Brien, 2007). Results Participants’ demographic characteristics and mean amounts of television watched are shown in Table 2. More than half of the children’s mothers were high school graduates or higher, and 17.2% of the children were classified as overweight or obese (BMI mean ± SE was 18.65 ± 0.09). The mean amount of television watched for all participants was 2.11 h/day. Overall, we found that participants usually watched television more often on weekends (3.12 h/day) than on weekdays (1.70 h/day). The mean amount of television watched in addition to computer, DVD, and video game use was 3.71 h/day. The average weekly frequencies of the children’s exposure to individual food category advertising from the five network channels during the 7-month period are shown in Table 3. In terms of all television food advertising, 52.8% was EDNP food advertising and 47.2% was

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Table 2 Participants’ demographic characteristics. No. of subjects (%) Gender Boys Girls Mother’s education ≤12 years >12 years Body mass index (BMI) categories Underweight or normal Overweight or obese

1183 (48.9) 1236 (51.1) 689 (42.2) 942 (57.8) 2003 (82.8) 415 (17.2) Mean ± SE

BMI Amount of television watched per week (h/day) Amount of television watched per weekday (h/day) Amount of television watched per weekend (h/day) Amount of television watched and computer use (h/day)1 1

18.65 ± 0.09 2.11 ± 0.04 1.70 ± 0.04 3.12 ± 0.07 3.71 ± 0.07

Sum of television, computer, DVD, and game time; h/day = hours/day.

non-EDNP food advertising. The food category with the highest advertising exposure of all food advertising (EDNP and non-EDNP) was dairy products. An average of 55.5 dairy product advertisements were viewed weekly per channel (comprising 15.7% of all food advertisements); cereal advertisements were the second most viewed advertisements (12%). Among EDNP foods, non-alcoholic sweetened beverage advertisements were the most viewed, comprising 10.1% of all EDNP advertisements. Advertisements for instant noodles (ramen) were the second most frequently viewed (7.5%). Participant preferences for each advertised food category according to exposure to television advertising for each EDNP food are shown in Table 4. EDNP food preferences differed significantly between quartiles, with the exception of pie snacks. Increases in television exposure to advertising for fried snacks, chocolates, sweets,

Table 3 The average weekly number of television food advertisements per television channel. Energy-dense/nutrient-poor food advertising

Average frequency/ week (%)

Non-alcoholic sweet beverage (iced tea, shakes, sport drinks, sweetened beverages, etc.) Instant noodles (ramen) Fried chicken Pizza Fried snacks (chips, snack foods) Ice cream Soft drinks (Coke, Sprite) Chocolates and processed chocolates Candy and gum Hamburgers Cakes and doughnuts Fruit-flavored juices Pie snacks

35.8 (10.1) 26.4 (7.5) 24.1 (6.8) 20.7 (5.9) 17.5 (4.9) 15.0 (4.2) 14.6 (4.1) 9.4 (2.7) 7.0 (2.0) 5.4 (1.5) 4.5 (1.3) 4.0 (1.1) 2.6 (0.7)

Non-energy-dense/nutrient-poor food advertising Milk, cheese, and other dairy products Cereals Coffee Foods from restaurants Fruit juices Fruits Water and tea Soy milk Sausage and ham Baked snacks (non-sweet crackers) Vegetables Total

55.5 (15.7) 42.5 (12.0) 23.4 (6.6) 12.6 (3.6) 9.9 (2.8) 8.4 (2.4) 5.3 (1.5) 5.3 (1.5) 2.5 (0.7) 1.1 (0.3) 0.4 (0.1) 353.9 (100)

cakes and doughnuts, ice cream, fruit-flavored juices, soft drinks, non-alcoholic beverages, pizza, hamburgers, fried chicken, and instant noodles were associated with increases in children’s preferences for the respective food categories. However, the association disappeared after we adjusted for the amount of television watched. Table 5 presents children’s weekly EDNP food intake according to EDNP food advertising quartile. We found that participant intake of advertised foods increased with increased exposure to television advertisements for EDNP foods, with the exception of fruitflavored juices, pizza, and hamburgers; intake also differed significantly between advertising exposure quartiles for fried snacks, pie snacks, chocolates, sweets, cakes and doughnuts, ice cream, soft drinks, beverages, and instant noodles. In addition, lower intake of fruit (P = 0.002; P for linear trend = 0.001) and vegetables (P < 0.001; P for linear trend <0.001) was found as exposure to total EDNP food advertising increased. This association was non-significant for all foods after adjusting for the amount of television watched. The odds ratios for being overweight or obese according to the amount of television watched and exposure to EDNP food category advertising are shown in Table 6. Children in the highest television viewing quartile had three times the risk of being overweight or obese relative to children in the lowest quartile (odds ratio, 2.86; P for linear trend <0.001). Children in the highest total EDNP food advertising exposure quartile had twice the risk of being overweight or obese (odds ratio, 2.41; P for linear trend <0.001). Each EDNP food advertising and total EDNP food advertising exposure (sum of all EDNP food advertising) were also related to a linearly increased risk of being overweight or obese; however, this linear relationship disappeared for all foods after adjusting for the amount of television watched. Discussion We found that television exposure to EDNP food advertising may be associated with an increased risk of being overweight or obese and EDNP food preference and intake; however, the total amount of television watched may have a larger effect on risk, preference, and intake. Several studies have also suggested that children’s exposure to EDNP food advertising might encourage consumption of EDNP foods and may need to be restricted as a result (Chou et al., 2008; Lobstein & Dibb, 2005; Zimmerman & Bell, 2010). Our results demonstrating an association between preference and exposure to television advertising for the 13 EDNP food categories are in accordance with previous studies. One study recently found that children preferred food items that had been advertised, and children who watched television more often appeared to be more responsive to food advertising than those who watched less television (Boyland et al., 2011). Even brief exposure to food advertising through recordings influenced children’s food preferences (Borzekowski & Robinson, 2001). Our study revealed that intake of food from most EDNP food categories was associated with exposure to television advertising for EDNP foods before adjusting for the amount of television watched. Conversely, intake of pizza and hamburgers was not associated with exposure to their respective advertisements, even without adjusting for the amount of television watched. In South Korea, the increase in the prevalence of obesity and chronic disease has often been attributed to the Westernization of diets, particularly the consumption of high fat foods such as fast foods. In response, several educational and public health campaigns have been implemented to influence fat consumption in an attempt to reduce the obesity rate (Lee, Popkin, & Kim, 2002). Our findings may raise awareness of the risk of fast food to the Korean public and help inform programs or legislations to improve the health of children. It is important to note that exposure to all EDNP food advertising (the sum of all EDNP food advertising) was negatively

B. Lee et al./Appetite 81 (2014) 305–311

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Table 4 Preferences for each advertised food category according to exposure to energy-dense/nutrient-poor (EDNP) food television advertising (mean ± SE)1. Quartile of exposure to EDNP food advertising2 Q1 Fried snacks Pie snacks Chocolates Sweets Cakes, doughnuts Ice cream Fruit-flavored juices Soft drinks Non-alcoholic beverages Pizza Hamburgers Fried chicken Instant noodles (ramen) 1 2 3 4 5

Q2

3.40 ± 0.06 2.96 ± 0.06 3.24 ± 0.07a 3.06 ± 0.06a 3.28 ± 0.07a 4.20 ± 0.05a 3.65 ± 0.06a 3.28 ± 0.06a 3.63 ± 0.07a 3.55 ± 0.07a 3.52 ± 0.07a 3.70 ± 0.07a 3.46 ± 0.06a a

Q3

3.49 ± 0.06 3.03 ± 0.06 3.27 ± 0.06a 3.19 ± 0.05a 3.31 ± 0.06a 4.16 ± 0.04a 3.80 ± 0.05ab 3.32 ± 0.07a 3.81 ± 0.06b 3.70 ± 0.06a 3.62 ± 0.07ab 3.84 ± 0.05a 3.57 ± 0.05ab ab

Q4

3.52 ± 0.05 3.10 ± 0.06 3.25 ± 0.07a 3.21 ± 0.07ab 3.48 ± 0.06b 4.14 ± 0.05a 3.77 ± 0.06a 3.38 ± 0.07a 3.70 ± 0.06ab 3.62 ± 0.07a 3.71 ± 0.06bc 3.85 ± 0.06a 3.67 ± 0.05b b

3.72 ± 0.05 3.11 ± 0.05 3.48 ± 0.05b 3.36 ± 0.06b 3.54 ± 0.06b 4.33 ± 0.04b 3.94 ± 0.06b 3.75 ± 0.06b 4.01 ± 0.05c 3.94 ± 0.05b 3.83 ± 0.06c 4.01 ± 0.05b 3.84 ± 0.05c c

P3

P4

P5

<0.001 0.233 0.008 0.003 0.005 0.014 0.011 <0.001 <0.001 <0.001 0.003 0.001 <0.001

<0.001 0.042 0.013 <0.001 0.001 0.066 0.003 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001

0.149 0.935 0.936 0.962 0.431 0.055 0.150 0.139 0.499 0.139 0.544 0.462 0.070

Preference was rated from 1 “dislike very much” to 5 “like very much”. Exposure to advertisements for each type of EDNP food was divided into quartiles (Q1: <25%, Q2: 25–50%, Q3: 50–75%, Q4: ≥75%). Analyzed using ANOVA; different letters in columns Q1, Q2, Q3, and Q4 indicate significantly different values. P for linear trend. P for linear trend adjusting for total amount of television watched.

that television viewing may be more predictive of obesity than advertising because sedentary and snacking behavior as well as exposure to advertising are all increased as we increase television viewing (Council on Communications and Media, 2011; Halford et al., 2004). As a result, it is difficult to determine the actual effect of advertising alone. One study showed the effect of viewing commercials, rather than just television, by distinguishing between programs that included commercials and those that did not. However, the study did not take the number of commercials shown during the programs into account and only considered the length of program time that included commercials (Zimmerman & Bell, 2010). Chou et al. (2008) used weekly hours of fast food advertisements aired and total weekly television viewing hours using spot television advertising with local variation to calculate viewing exposure (weekly hours of fast food advertising seen). Their study only included exposure to advertising (and excluded the amount of television watched) in the final regression model, because the amount watched was in direct proportion to the exposure. In our study, although television advertising exposure was measured using total viewing time and average number of food advertisements broadcast on an hourly basis, it was not in direct proportion to the amount of television

associated with the intake of healthy foods such as fruits and vegetables. Previous studies have found that exposure to advertising for healthy foods promoted intake of fruits and vegetables and positive attitudes toward those foods (Dixon et al., 2007; Geeroms, Verbeke, & Van Kenhove, 2008; Klepp et al., 2007). After exposure to advertisements, children’s food preferences increased not only for EDNP foods but also for healthier foods such as vegetables (Goldberg, Gorn, & Gobson, 1978; Nicklas et al., 2011). Our results suggest that exposure to food advertising, both for EDNP and healthier food options, is associated with children’s eating behaviors. Increased exposure to healthy food advertising, in place of EDNP food advertising, may help to promote healthier eating habits among children (Dixon et al., 2007; Geeroms et al., 2008). In our study, we did not observe an association between intake of fruits and vegetables and advertising, due to a lack of advertisements for those foods. However, we concluded that less exposure to television advertising for EDNP foods may be associated with an increased intake of fruits and vegetables. All associations between exposure to food advertising and preference, intake, and being overweight or obese disappeared after we adjusted for the total amount of television watched. In fact, we found

Table 5 Weekly frequencies of food intake according to exposure to individual and total energy-dense/nutrient-poor (EDNP) food television advertising (mean ± SE)1. Quartile of exposure to EDNP food advertising

Fried snacks1 Pie snacks1 Chocolates1 Sweets1 Cakes, doughnuts1 Ice cream1 Fruit-flavored juices1 Soft drinks1 Non-alcoholic beverages1 Pizza1 Hamburgers1 Fried chicken1 Instant noodles (ramen)1 Vegetables2 Fruits2 1 2 3 4 5

Q1

Q2

Q3

Q4

P3

P4

P5

1.67 ± 0.16a 1.11 ± 0.12a 1.52 ± 0.15a 1.72 ± 0.14a 1.58 ± 0.15a 3.76 ± 0.18a 1.85 ± 0.17 1.50 ± 0.13a 1.90 ± 0.16a 0.80 ± 0.11 0.79 ± 0.11 0.99 ± 0.12 2.66 ± 0.25a 12.69 ± 0.56a 7.81 ± 0.27a

1.66 ± 0.12a 1.32 ± 0.13ab 1.67 ± 0.14a 2.02 ± 0.14ab 1.70 ± 0.14a 4.08 ± 0.18ab 1.84 ± 0.15 1.50 ± 0.12a 2.20 ± 0.14ab 0.85 ± 0.08 0.91 ± 0.11 0.96 ± 0.08 3.00 ± 0.20a 10.35 ± 0.46b 6.70 ± 0.23b

1.94 ± 0.15a 1.55 ± 0.17bc 1.87 ± 0.17ab 2.27 ± 0.15b 1.97 ± 0.15ab 4.40 ± 0.19bc 1.73 ± 0.15 1.99 ± 0.18b 2.52 ± 0.18bc 0.82 ± 0.10 0.86 ± 0.13 1.28 ± 0.12 3.61 ± 0.24bc 9.78 ± 0.46b 6.73 ± 0.25b

2.47 ± 0.20b 1.73 ± 0.14c 2.09 ± 0.15b 2.86 ± 0.20c 2.16 ± 0.17b 4.86 ± 0.20c 2.19 ± 0.19 2.20 ± 0.16b 2.77 ± 0.17c 1.15 ± 0.16 0.87 ± 0.11 1.24 ± 0.12 4.02 ± 0.23c 9.50 ± 0.45b 6.52 ± 0.27b

0.004 0.008 0.041 <0.001 0.042 <0.001 0.296 <0.001 0.001 0.286 0.889 0.078 <0.001 <0.001 0.002

0.001 0.001 0.004 <0.001 0.005 <0.001 0.255 <0.001 <0.001 0.088 0.709 0.047 <0.001 <0.001 0.001

0.643 0.399 0.291 0.436 0.804 0.898 0.549 0.965 0.279 0.682 0.259 0.375 0.854 0.091 0.620

Exposure to EDNP food advertising was divided into quartiles (Q1: <25%, Q2: 25–50%, Q3: 50–75%, Q4: ≥75%). Exposure to total EDNP food advertising was divided into quartiles (Q1: <25%, Q2: 25–50%, Q3: 50–75%, Q4: ≥75%). Analyzed by ANOVA, different letters in columns Q1, Q2, Q3, and Q4 indicate significantly different values. P for linear trend. P for linear trend adjusting for total amount of television watched.

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Table 6 Odds ratios (95% CI) for being overweight/obese according to the amount of television watched and exposure to television advertising for EDNP food. By quartile of the amount of television watched, exposure to each and total EDNP food advertising

Amount of television watched EDNP food advertising2 Fried snacks Pie snacks Chocolates Sweets Cakes, doughnuts Ice cream Fruit-flavored juices Soft drinks Non-alcoholic beverages Pizza Hamburgers Fried chicken Instant noodles (ramen) Total EDNP food advertising3 1 2 3 4 5 6

1

Q1

Q2

Q3

Q4

P4

P5

1.00

1.58 (0.99–2.54)

2.12 (1.35–3.34)

2.86 (1.86–4.40)

<0.001

<0.001

1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

1.05 (0.66–1.67) 1.17 (0.74–1.85) 1.10 (0.70–1.74) 1.36 (0.86–2.16) 1.04 (0.65–1.66) 1.37 (0.86–2.18) 2.01 (1.28–3.15) 0.99 (0.63–1.57) 1.12 (0.70–1.77) 0.78 (0.50–1.23) 0.98 (0.65–1.54) 1.02 (0.64–1.60) 1.14 (0.72–1.82) 1.10 (0.69–1.76)

1.78 (1.17–2.71) 1.57 (1.02–2.40) 1.49 (0.97–2.27) 1.61 (1.04–2.48) 1.61 (1.06–2.43) 1.90 (1.23–2.94) 1.59 (1.04–2.43) 1.49 (0.98–2.28) 1.46 (0.97–2.20) 1.24 (0.82–1.89) 1.49 (0.96–2.30) 1.28 (0.83–1.95) 1.62 (1.07–2.46) 1.64 (1.07–2.52)

2.07 (1.38–3.10) 2.11 (1.40–3.17) 2.17 (1.46–3.23) 2.41 (1.59–3.64) 2.57 (1.71–3.88) 2.38 (1.57–3.63) 2.36 (1.55–3.58) 2.19 (1.43–3.34) 2.26 (1.50–3.41) 2.28 (1.50–3.46) 1.85 (1.23–2.77) 2.20 (1.49–3.26) 2.39 (1.57–3.63) 2.41 (1.60–3.63)

<0.001 0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.002 <0.001 <0.001 <0.001

<0.001 <0.001 <0.001 0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001

P6

0.873 0.680 0.783 0.786 0.178 0.735 0.358 0.667 0.655 0.240 0.892 0.370 0.660 0.990

The amount of television watched was divided into quartiles (Q1: <25%, Q2: 25–50%, Q3: 50–75%, Q4: ≥75%). Exposure to each EDNP food advertising group was divided into quartiles (Q1: <25%, Q2: 25–50%, Q3: 50–75%, Q4: ≥75%). Exposure to total EDNP food advertising was divided into quartiles (Q1: <25%, Q2: 25–50%, Q3: 50–75%, Q4: ≥75%). Analyzed by logistic regression at P < 0.05. P for linear trend. P for linear trend adjusting for total amount of television watched.

watched. Therefore, we showed regression models both with and without total television viewing time. Since advertisement-free television viewing, having a sedentary lifestyle, and snacking while watching television were associated with total television viewing, it is not surprising to see the effect of advertising exposure disappear after adjusting for these three factors in the model. There were some limitations in our study. First, we could not determine a causal relationship between television food advertising and food intake, food preference, or obesity, due to the crosssectional study design. Second, although we recorded the times at which participants usually watched television, we did not know which channels were watched or how many advertisements were shown on each channel; therefore, we could not individualize exposure based on the channels watched. There may have been a channel showing very few advertisements during a particular time period relative to the other four channels. Third, the FFQ was limited in assessing overall dietary intake, as it focused primarily on the 13 EDNP food categories alone. Last, due to height and weight being self-reported, overweight or obesity status may have been underestimated due to inaccurate responses. The primary strength of our study was that we separated television advertising from numbers of viewing hours. Estimates of exposure to television advertising were directly calculated using the number of advertisements broadcast on an hourly basis on the most popular channels during a 7-month period. Therefore, we used a unique approach to examine the associations between long-term exposure to advertising for individual and total EDNP food categories and food preference, food intake, and obesity in children. Another strength of our study was the use of a large, representative sample of fifth-grade South Korean children. To the best of our knowledge, this is the first comprehensive study to examine the association between individual exposure to EDNP food advertising on television and obesity, food intake, and food preference. Although we could not conclude that exposure to EDNP food advertising on television was associated with being overweight or obese, food preference, or consumption of EDNP foods (because we could not examine the exclusive effect of exposure to television food advertising), we found a possible association between exposure to television food advertising and being overweight or obese, food preference, and consumption of EDNP foods. Television food advertis-

ing may play an important role in increasing the risk of childhood obesity and unhealthy dietary behaviors. In nations such as the U.K., Canada, the U.S.A., Australia, and South Korea, regulation of advertising to children has already been implemented to improve health environments and promote better eating habits among children. Our study suggests that it may be necessary to increase public health campaigns and reduce EDNP food advertisements to assist in decreasing the incidence and prevalence of obesity. Additional longitudinal studies are needed to understand the causality of the exclusive effect of advertising. Furthermore, the effect of legislation restricting the advertisement of EDNP foods should be reevaluated to establish a clearer understanding of the effects of food advertising on consumer health habits and provide more concrete and supportive evidence.

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