Appetite 71 (2013) 388–395

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Appetite

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Research report

The impact of nutritional policy on socioeconomic disparityin the unhealthy food intake among Korean adolescents q

0195-6663/$ - see front matter � 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.appet.2013.09.010

q Conflict of interest: There are no conflicts of interest. There are no sources offinancial support.⇑ Corresponding author.

E-mail address: kwoh27@korea.kr (K.W. Oh).

Kirang Kim a, Sun Min Park b, Kyung Won Oh b,⇑a Department of Food Science and Nutrition, College of Natural Science, Dankook University, 119, Dandae-ro, Dangnam-gu, Cheonan-si, Chungnam 330-714, Republic of Koreab Division of Health and Nutrition Survey, Korea Centers for Disease Control and Prevention, 187 Osongsaengmyeong2-ro, Osong-eup, Cheongwon-gun, Chungcheoncbuk-do363-951, Republic of Korea

a r t i c l e i n f o

Article history:Received 3 February 2013Received in revised form 7 September 2013Accepted 10 September 2013Available online 19 September 2013

Keywords:Unhealthy food intakeNutritional policySocioeconomic disparityAdolescents

a b s t r a c t

The objectives of this study were to examine the trend in unhealthy food intake by socioeconomic posi-tion (SEP) and to determine whether the government’s nutritional policies affect socioeconomic disparityin the food intake among adolescents. Data were from the six independent cross-sectional survey data(2006–2011) of Korea Youth Risk Behavior Web-based Survey and included 445,287 subjects aged 12–18 years. The unhealthy food intake was assessed by food frequency intake and SEP was evaluated withthe family affluence scale. We observed that unhealthy food intakes decreased through the years, show-ing the apparent decline when nutritional policies focusing on the restriction of unhealthy foods wereimplemented, and the trend was all same in the different SEP groups. The pattern of unhealthy foodintakes by SEP has changed before and after implementation of the policies. The intakes of carbonatedbeverages, fast food, and confectioneries were higher in the higher SEP group before implementationof the policies but the difference was not shown after implementation of the policies. The intake ofinstant noodles was consistently higher in the lower SEP group. The risk of frequent consumption ofunhealthy foods was generally more decreased through the years in the higher SEP group than the lowerSEP group. In conclusion, this study found the positive effect of nutritional policy on unhealthy foodintake among adolescents and the high SEP group appeared to undergo greater desirable changes in die-tary behaviors after implementation of nutritional policies than the low SEP group.

� 2013 Elsevier Ltd. All rights reserved.

Introduction

Socioeconomic inequalities in health are seen at all ages(Gwatkin et al., 2007; Starfield, Riley, Witt, & Robertson, 2002;Wagstaff, 2000) and are known to be substantially attributed to so-cial differences in modifiable health-related behaviors such as diet,physical activity, or smoking, in that lower socioeconomic groupshave higher prevalence rates of unhealthy behaviors (Dowler,2001; James, Nelson, Ralph, & Leather, 1997; Marmot & Wilkinson,2006). Given that modifiable health-related behaviors are gener-ally established early in life (Ferreira, Twisk, van Mechelen,Kemper, & Stehouwer, 2005; Kelder, Perry, Klepp, & Lytle, 1994),preventing the development of these inequalities in unhealthybehaviors during childhood and adolescence is important in tack-ling socioeconomic inequalities in health. Thus, differences in thefood intake of children and adolescents by socioeconomic position

(SEP) need to be monitored over time. Previous studies, however,have been limited to general trends in dietary intake by age, sex,or ethnicity (Alexy & Kersting, 2003; Kant & Graubard, 2011;Moreno et al., 2010).

The relationship between SEP and diet quality among childrenand adolescents has been reported. Children and adolescents inlower socioeconomic households consume more unhealthy foodsin the western countries (Darmon, Ferguson, & Briend, 2003; Jameset al., 1997; Vereecken, Inchley, Subramanian, Hublet, & Maes,2005; Xie, Gilliland, Li, & Rockett, 2003). This disparity could widenthe gap in health outcomes, including obesity, between socioeco-nomic groups (James et al., 1997). One strategy to reduce theinequality in dietary intake would be changes in social, economic,physical, and educational environments to encourage healthy foodchoices (Larson, Story, & Nelson, 2009; Lovasi, Hutson, Kathryn, &Neckerman, 2009), and these changes could be effectively createdor modified by policies, laws, regulations, and programs imple-mented by the government, community, and schools (de Sa & Lock,2008; Jaime & Lock, 2009; Sallis & Owen, 2002). There is some evi-dence supporting the positive effect of actions taken by the govern-ment or schools to improve dietary behavior during childhood andadolescence (de Sa & Lock, 2008; Jaime & Lock, 2009), but little is

Table 1Government nutrition policy to influence adolescents’ dietary intake in the Republicof Korea.

Calendaryear

Government nutrition policy

March 2006 Recommendation of a ban on carbonated beverages in schoolsand youth training facilities

July 2006 Amendment to the School Meal ActSeptember

2006Dissemination of a standardized obesity prevention program

February2007

Ban on carbonated beverages in schools and youth trainingfacilities

March 2008 Enforcement of mandatory nutritional labeling on schoolmeals

March 2008 Enactment of the Special Act on the Safety Management ofChildren’s Dietary Life

K. Kim et al. / Appetite 71 (2013) 388–395 389

known about their effects on the socioeconomic inequality in die-tary behavior in youth.

Korean adolescents have increasingly irregular eating behaviorand westernized dietary patterns, resulting in an unhealthy dietand unbalanced nutritional status (Korea Centers for DiseaseControl and Prevention, 2010; Song, Park, Paik, & Joung, 2010). Inresponse to these problems, the Korean government has beenintroducing nutritional policies targeting the school food environ-ment since 2006 (Table 1). A recent study tried to evaluate adoles-cent dietary behavior before and after implementation of thepolicies (Bae et al., 2012). However, the study did not provide suf-ficient evidence of the policies’ effect because the analysis wasundertaken too soon after full policy implementation. Therefore,the objective of this study was to examine the trends in unhealthyfood intake by SEP and to determine whether the government’snutritional policies affect unhealthy food intake and the socioeco-nomic disparity in the food intake among adolescents using na-tional, representative data sets.

Methods

Data sources and study subjects

Data were derived from the Korea Youth Risk Behavior Web-based Survey (KYRBS), which has been performed every year since2005 by the Korea Centers for Disease Control and Prevention tomonitor the prevalence of health behaviors among adolescentsand progress toward national health objectives with planningand assessment of adolescent health promotion policies. The sur-vey is an ongoing, web-based survey conducted on a nationallyrepresentative sample of middle and high school students with astratified, clustered, multistage probability sampling design. Thestudents provided written consent for the survey and respondedelectronically to a questionnaire consisting of 134 indicators on14 health behaviors during one teaching session, which took placein a computer room at the sampled schools. Each session was man-aged by a trained support teacher. The reliability and validity ofKYRBS has been shown to be good (Bae et al., 2010; Korea Centersfor Disease Control and Prevention, 2009). The requirement forethics approval for use of the publicly available KYRBS data waswaived by the IRB.

Unhealthy food intake

The adolescents’ unhealthy food intakes were assessed by thefour indices in KYRBS: (1) During the last week, how often didyou drink carbonated beverages? (2) During the last week, how of-ten did you eat fast foods such as pizza, hamburgers, and friedchicken? (3) During the last week, how often did you eat instant

noodles? (4) During the last week, how often did you eat confec-tioneries including chips and chocolate? Each item had seven re-sponse options: not at all, 1 or 2 times per week, 3 or 4 timesper week, 5 or 6 times per week, once a day, twice a day, or threeor more times a day.

Socioeconomic position

The indicator of SEP for adolescents in this study was the FamilyAffluence Scale (FAS), which was developed and used in Europeancountries as a good predictor of socioeconomic differentials inhealth (Currie et al., 2008). A recent study showed that the FAS ap-peared to be useful as a measure of SEP for Korean adolescents(Cho & Khang, 2010). The scale consists of four items: (1) Does yourfamily have a car? (no, one, two or more), (2) Do you have yourown room? (no, yes), (3) During the past year, how many timesdid you travel away on holiday with your family? (not at all, once,twice, three times or more), and (4) How many computers do youhave in your household? (none, one, two, three or more). Each itemwas given a score of 0 if the answer was no or not at all, 1 if theanswer was yes, one, or once, 2 if the answer was two or more,twice or two, and 3 for the rest of the responses. The compositeFAS score was calculated by summing the responses to these fouritems and the scores were then grouped as low (score of 0–2), mid-dle (score of 3–5), or high (score of 6–9) (Boudreau & Poulin, 2009).

Data analysis

Because the Family Affluence Scale (FAS) as an indicator of SEPwas measured starting in 2006, this study used survey data from2006 to 2011. For each survey year, all results were estimatedusing sampling weight for the respondent’s probability of being se-lected for the sex-, grade-, and school type-specific distributionsfor the region based on education statistics from the Ministry ofEducation. The secular linear trend during the entire period was as-sessed by logistic regression analyses, using each year as anexplanatory variable and each dietary behavior index as a depen-dent variable. Logistic regression analysis was also used to assesssocioeconomic disparity in undesirable food consumption pattern.In order to compare the risk of undesirable food consumption pat-tern among SEP groups, odds ratio of frequent consumption de-fined as at least three or more consumption per week was usedfor the four unhealthy foods (carbonated beverages, fast food, in-stant noodles, and confectioneries). The model was adjusted forage, sex, school type (middle school, general high school, and voca-tional high school), region (metro city, small city, and rural area),body mass index (kg/m2), and exercise (intensive physical activityfor more than 20 minutes per day for 3 days or more for the past7 days). The effects of particular policies were indirectly evaluatedby comparing the annual mean value of unhealthy food frequencyconsumption before and after the policies were implemented. Allanalyses were done using SAS version 9.2 (SAS Inc., Cary, NC, USA).

Results

Participation rates for each survey year from 2006 to 2011 were90.9%, 94.8%, 95.1%, 97.6%, 97.7%, and 95.5% respectively (KoreaCenters for Disease Control and Prevention, 2011). The total num-ber of subjects was 71,404 for 2006, 74,698 for 2007, 75,238 for2008, 75,066 for 2009, 73,238 for 2010, and 75,643 for 2011. Theproportion of boys ranged from 52.3% to 53.3% among middleschool students and from 52.8% to 53.1% for those in high schoolacross the survey years. The proportion of subjects in the highersocioeconomic group was higher than in the lower socioeconomicgroup across all survey years for both boys and girls. The mean age

390 K. Kim et al. / Appetite 71 (2013) 388–395

of subjects was about 15 years old and the mean value of bodymass index was 20 kg/m2 in all survey years. The proportion ofexercise had an increased trend during the study period (Table 2).

The age-, school type-, and region-adjusted mean values of un-healthy food frequency consumption by survey year and SEP wereshown in Fig. 1. The mean value of unhealthy food frequency con-sumption generally showed a consistent trend over time, regard-less of SEP and both sexes. This trend gradually decreased duringthe period of 2006–2008, dramatically decreased between 2008and 2009, and then decreased or stabilized from 2009 to 2011.All of these decreasing trends were significant (p-trend < 0.0001).The mean values of food frequency consumption according toSEP group had different trends across the survey years and by fooditem. In terms of carbonated beverage, fast food and confectioner-ies intake, the high SEP group generally consumed more of theseitems than the low SEP group during 2006–2008, whereas their in-take was similar from 2009 to 2011. Regarding instant noodles, thelow SEP group reported eating more instant noodles through theyears.

As compared with girls, boys had higher frequency of carbon-ated beverage, fast food and instant noodle consumption (Fig. 2).Regarding carbonated beverage, fast food and confectioneries in-take, the significant difference by SEP in these food consumptionduring the period of 2006–2008 was shown in only boys. Interest-ingly, for carbonated beverage intake of girls, there was no signif-icant difference of the consumption by SEP during the period of2006–2008 but in 2009 and 2010, girls with low SEP had higherfrequency consumption than those with high SEP.

In order to assess the trend of socioeconomic disparity in unde-sirable food intake pattern, the odds ratios of frequent consump-tion (three or more consumption per week) of unhealthy foodsaccording to level of SEP were presented by the survey year, afteradjusting for age, school type, region, body mass index, and exer-cise. The high SEP group had higher risk of frequent consumptionof carbonated beverages and fast food than the low SEP group dur-ing 2006–2008, but the higher risk in the high SEP group was not

Table 2Distribution of study subjects by survey year and gender.

‘06 ‘07 ‘08

Total 71,404 74,698 75,238Age (year)a 14.9 (12.0–18.0) 15.0 (12.0–18.0) 15.0 (12.0–BMI (kg/m2)a 20.5 (10.2–32.0) 20.5 (10.8–31.7) 20.5 (10.4–Exerciseb 71,404 (31.9) 74,698 (29.9) 75,238 (31.SEPc

Low 11,691 (15.4) 11,174 (13.8) 10,917 (13.Middle 40,490 (56.0) 42,075 (55.8) 42,797 (56.High 19,223 (28.7) 21,449 (30.4) 21,524 (30.

Boys 37,204 39,466 39,278Age (year)a 14.9 (12.0–18.0) 15.0 (12.0–18.0) 15.0 (12.0–BMI (kg/m2)a 20.9 (10.2–32.0) 20.8 (10.8–31.7) 20.8 (10.4–Exerciseb 37,204 (44.9) 39,466 (41.6) 39,278 (42.SEPc

Low 6,208 (15.9) 5,702 (13.5) 5,432 (13.5Middle 20,812 (55.0) 22,271 (56.1) 22,339 (56.High 10,184 (29.1) 11,493 (30.4) 11,507 (30.

Girls 34,200 35,232 35,960Age (year)a 14.9 (12.0–18.0) 15.0 (12.0–18.0) 15.0 (12.0–BMI (kg/m2)a 20.1 (11.1–29.4) 20.1 (11.1–28.6) 20.0 (11.5–Exerciseb 34,200 (17.1) 35,232 (16.7) 35,960 (19.SEPc

Low 5,483 (14.9) 5,472 (14.1) 5,485 (14.0Middle 19,678 (57.0) 19,804 (55.5) 20,458 (56.High 9,039 (28.1) 9,956 (30.4) 10,017 (29.

a The values are mean value and range.b The values are number and percentage of persons who have done intensive physica

riding, fast swimming, and carrying heavy things) for more than 20 min per day for 3 dc The values are number and percentage, SEP = socioeconomic position.

shown from 2009 to 2011. The pattern of result was more evidentin boys than in girls. For instant noodle intake, the high SEP grouphad lower risk of frequent consumption than the low SEP groupthrough the years in both sexes, and the risk in the higher SEPgroup decreased over time (odds ratio 0.86 in 2006 vs 0.80 in2011 for total; 0.90 vs 0.83 for boys; 0.81 vs 0.74 for girls). Regard-ing confectioneries, the high SEP group appeared to have higherrisk of frequent consumption than the low SEP group throughthe years and the change of the risk over time was little (odds ratio1.06 in 2006 vs 1.07 in 2011 for total) (Table 3).

Discussion

Given that little is known about the trend in unhealthy food in-take according to SEP among adolescents and the impact of na-tional nutritional policies on the unhealthy food intake and itssocioeconomic disparity, this study sought to address this lack ofknowledge. We observed that the trends in unhealthy food intakeover time were similar among SEP groups, showing a dramaticallydecrease during the period in which nutritional policies focusingon the restriction of unhealthy foods were implemented. In termsof the difference of unhealthy food intake by SEP group, the differ-ence by SEP was significant in some unhealthy food intakes beforeimplementation of the policies but the differences were disap-peared after implementation of the policies.

As gradual changes to the increasingly westernized dietary pat-terns of Korean adolescents are related to an increased risk of beingoverweight (Song et al., 2010), various government-led nutritionalpolicies have been established during the past several years to ad-dress this issue (Kim, 2011; Kwak, Kim, & Kim, 2010). The policiesare focused on changes to the school food environment and are re-lated to the regulation of school foods and food labeling, andrestriction of unhealthy foods that are high in energy and low innutrients. In particular, the Special Act on the Safety Managementof Children’s Dietary Life enacted in March 2008 and enforced in

‘09 ‘10 ‘11

75,066 73,238 75,64318.0) 15.1 (12.0–18.0) 15.1 (12.0–18.0) 15.2 (12.0–18.0)31.9) 20.4 (10.9–31.7) 20.5 (10.1–31.4) 20.5 (11.0–31.4)8) 75,066 (31.6) 73,238 (33.0) 75,643 (34.1)

8) 10,091 (12.8) 8,945 (11.6) 8,714 (10.9)3) 42,299 (55.6) 39,500 (52.9) 39,434 (51.8)0) 22,676 (31.6) 24,793 (35.5) 27,495 (37.3)

39,612 38,391 37,87318.0) 15.1 (12.0–18.0) 15.1 (12.0–18.0) 15.2 (12.0–18.0)31.9) 20.8 (10.9–31.7) 20.9 (10.1–31.4) 20.9 (11.0–31.4)8) 39,612 (43.3) 38,391 (45.3) 37,873 (46.9)

) 5,257 (12.9) 4,652 (11.8) 4,381 (11.2)1) 22,017 (55.1) 20,426 (52.3) 19,418 (51.3)4) 12,338 (3.02) 13,313 (35.9) 14,074 (37.5)

35,454 34,847 37,77018.0) 15.1 (12.0–18.0) 15.1 (12.0–18.0) 15.1 (12.0–18.0)28.9) 20.0 (11.5–28.6) 20.0 (11.9–28.9) 20.2 (11.3–29.1)3) 35,454 (18.4) 34,847 (19.3) 37,770 (20.0)

) 4,834 (12.7) 4,293 (11.4) 4,333 (10.6)4) 20,282 (56.3) 19,074 (53.6) 20,016 (52.4)6) 10,338 (31.0) 11,480 (35.0) 13,421 (37.1)

l activities (jogging, soccer, basketball, Taekwondo, mountain climbing, fast bicycleays or more for the past 7 days.

Fig. 1. Trends in the mean values of unhealthy food frequency intake per week by socioeconomic position (SEP). The solid line represents the high SEP, the dashed-dotted linerepresents the middle SEP, and the dotted line represents the low SEP. �p-Value < 0.05 for significant difference between high SEP group and low SEP group within a surveyyear. p-Values for linear trend of unhealthy food frequency intakes across survey years were all <0.0001.

K. Kim et al. / Appetite 71 (2013) 388–395 391

2009 includes the restriction of sales and advertising for highenergy and low nutritional food, the requirements for the qualitycertification of children’s favorite foods and the nutrition labelingetc. Especially, in order to protect young students from junk foods,the government decided to ban fast foods and soda within 200 m ofschools which are called ‘‘Green Food Zones’’ (Kwak et al., 2010).The dramatic decrease in the consumption of unhealthy foodscould be attributed to the implementation of these policies. Severalstudies reported that the restrictive nutrition policy to limit accessto and availability of unhealthy foods in school produced a positiveimpact decreasing the purchase of the unhealthy foods (Cullen,Watson, Zakeri, & Ralston, 2006; French, Story, Fulkerson, &Gerlach, 2003). Nevertheless, policies focusing only on the regula-tion of unhealthy foods or on the school nutrition environmentcould be limited to improve dietary behavior among adolescents(Jaime & Lock, 2009; Story, Kaphingst, Robinson-O’Brien, & Glanz,2008). Thus, the government’s further efforts to develop compre-hensive policies including improvement of out of school diets withan increase of accessibility to healthy foods such as fruit and veg-etable should be considered.

In this study, the decreased trend of unhealthy food intakeover time was consistent among SEP groups, but the differencesof unhealthy food intake by SEP were shown across survey years.The consumption of carbonated beverages, fast food and confec-tioneries was higher in the high SEP group but the significant dif-

ference was not shown in carbonated beverages and fast foodafter the implementation of nutritional policies. The instant noo-dle intake was consistently higher in the low SEP group. Manyprevious studies found that the lower SEP group consumed moreunhealthy foods with high energy density and low nutritional va-lue (Aranceta, Perez-Rodrigo, Ribas, & Serra-Majem, 2003; Jameset al., 1997; Vereecken et al., 2005; Xie et al., 2003) because ofthe generally low cost of these foods (Darmon & Drewnowski,2008). However, the weight of economic determinants in pur-chasing unhealthy foods would be different for food items be-tween countries. Some unhealthy foods could be consideredexpensive foods, thus being affordable to the higher SEP group.Several studies have reported a higher intake of soft drinks andfast foods in higher SEP groups among adolescents in centraland eastern European countries (Vereecken et al., 2005), Mexico(Ortiz-Hernández & Gómez-Tello, 2008), and China (Shi, Lien, Ku-mar, & Holmboe-Ottesen, 2005).

In Korea, fast food and instant noodle are commonly consumedas a substitute for a meal by Korean adolescents (Lee, Lee, Jeon, &Joo, 2008). However, because of relatively higher price of fast foodin Korea, fast food could be more accessible to adolescents withhigh SEP (Lee, Han, & Son, 2007). On the other hand, instant noo-dles could be preferred to adolescents with low SEP because drypackaged instant noodles are energy-rich, shelf-stable, andcost-effective (Drewnowski, 1998; Lee et al., 2007). The lower

Fig. 2. Trends in the mean values of unhealthy food frequency intake per week by socioeconomic position (SEP) and gender. (A) Carbonated beverage intake; (B) fast foodintake; (C) instant noodle intake; (D) confectionery intake. The solid line represents the high SEP, the dashed-dotted line represents the middle SEP, and the dotted linerepresents the low SEP. � p-Value < 0.05 for significant difference between high SEP group and low SEP group within a survey year. p-Values for linear trend of unhealthy foodfrequency intakes across survey years were all <0.0001.

392 K. Kim et al. / Appetite 71 (2013) 388–395

consumption of carbonated drinks and confectioneries amongadolescents in the low SEP group may be due to the fact that theyare unable to afford these snack food items with their limitedpocket money. According to results of the 2009 Korea NationalHealth and Nutrition Examination Survey, the frequency of snackconsumption is lower in low SEP groups than in high SEP groups(Korea Centers for Disease Control and Prevention, 2010).

Interestingly, this study found that consumption of carbonatedbeverages and fast food was higher in the high SEP group beforeimplementation of nutritional policies but the difference by SEPwas not shown after that. In addition, the risk of frequent con-sumption of unhealthy foods relatively more decreased throughthe years in the high SEP group than the low SEP group. This find-ing might imply that the policies seemed to be more effective in

Fig. 2 (continued)

Table 3Multivariate-adjusted odds ratios (95% confidence interval) of three or more consumption per week of unhealthy foods according to level of socioeconomic position (SEP).

Carbonated beverage Fast food Instant noodle Confectioneries

LowSEP

MiddleSEP

HighSEP

LowSEP

MiddleSEP

HighSEP

LowSEP

MiddleSEP

HighSEP

LowSEP

MiddleSEP

HighSEP

Totala

‘06 1.00 1.03(0.98–1.09)

1.23(1.16–1.31)

1.00 1.00(0.94–1.07)

1.22(1.14–1.30)

1.00 0.90(0.85–0.95)

0.86(0.81–0.92)

1.00 1.03(0.98–1.09)

1.06(0.99–1.13)

‘07 1.00 1.03(0.98–1.09)

1.19(1.13–1.26)

1.00 1.07(1.02–1.13)

1.36(1.28–1.44)

1.00 0.93(0.89–0.98)

0.88(0.83–0.93)

1.00 1.09(1.03–1.15)

1.18(1.11–1.25)

‘08 1.00 1.00(0.95–1.06)

1.17(1.10–1.24)

1.00 1.09(1.03–1.16)

1.33(1.25–1.42)

1.00 0.91(0.87–0.96)

0.90(0.85–0.96)

1.00 1.14(1.07–1.20)

1.21(1.14–1.29)

‘09 1.00 0.94(0.88–1.00)

1.02(0.95–1.09)

1.00 0.91(0.85–0.98)

1.08(1.00–1.17)

1.00 0.84(0.80–0.89)

0.79(0.75–0.84)

1.00 1.03(0.97–1.08)

1.10(1.04–1.17)

‘10 1.00 0.86(0.81–0.92)

0.96(0.89–1.03)

1.00 0.87(0.80–0.95)

1.05(0.96–1.15)

1.00 0.90(0.84–0.96)

0.80(0.75–0.86)

1.00 1.03(0.97–1.09)

1.08(1.02–1.15)

‘11 1.00 0.90(0.85–0.96)

0.99(0.93–1.05)

1.00 0.88(0.82–0.95)

1.00(0.92–1.08)

1.00 0.85(0.80–0.91)

0.80(0.75–0.85)

1.00 1.02(0.97–1.07)

1.07(1.01–1.13)

Boysb

‘06 1.00 1.06(0.98–1.15)

1.31(1.21–1.43)

1.00 1.01(0.94–1.09)

1.26(1.16–1.37)

1.00 0.93(0.86–1.00)

0.90(0.84–0.97)

1.00 1.05(0.97–1.13)

1.10(1.01–1.20)

‘07 1.00 1.04(0.96–1.12)

1.29(1.19–1.39)

1.00 1.09(1.01–1.18)

1.42(1.31–1.53)

1.00 0.95(0.88–1.02)

0.92(0.85–0.99)

1.00 1.14(1.06–1.23)

1.28(1.19–1.38)

‘08 1.00 1.02(0.95–1.09)

1.22(1.13–1.33)

1.00 1.14(1.05–1.24)

1.43(1.30–1.56)

1.00 0.95(0.89–1.02)

1.00(0.93–1.07)

1.00 1.14(1.05–1.24)

1.28(1.18–1.39)

‘09 1.00 0.95(0.88–1.02)

1.08(1.00–1.18)

1.00 0.89(0.80–0.98)

1.05(0.94–1.18)

1.00 0.89(0.83–0.96)

0.86(0.79–0.93)

1.00 1.03(0.96–1.12)

1.15(1.06–1.25)

‘10 1.00 0.90(0.82–0.97)

0.99(0.91–1.09)

1.00 0.81(0.73–0.90)

0.99(0.88–1.11)

1.00 0.95(0.87–1.02)

0.87(0.79–0.95)

1.00 0.99(0.91–1.08)

1.07(0.98–1.16)

‘11 1.00 0.90(0.83–0.97)

1.00(0.92–1.08)

1.00 0.85(0.77–0.94)

1.00(0.90–1.11)

1.00 0.84(0.78–0.91)

0.83(0.76–0.90)

1.00 0.99(0.92–1.07)

1.09(1.01–1.18)

Girlsb

‘06 1.00 0.99(0.92–1.07)

1.14(1.04–1.25)

1.00 0.98(0.89–1.08)

1.16(1.04–1.29)

1.00 0.85(0.79–0.93)

0.81(0.74–0.89)

1.00 1.00(0.93–1.08)

0.99(0.90–1.10)

‘07 1.00 1.03(0.96–1.10)

1.09(1.01–1.18)

1.00 1.05(0.97–1.13)

1.28(1.17–1.40)

1.00 0.92(0.86–0.99)

0.84(0.77–0.92)

1.00 1.03(0.95–1.11)

1.06(0.96–1.16)

‘08 1.00 0.98(0.91–1.05)

1.09(1.00–1.19)

1.00 1.04(0.94–1.14)

1.21(1.10–1.34)

1.00 0.87(0.81–0.94)

0.80(0.73–0.87)

1.00 1.13(1.04–1.22)

1.13(1.04–1.22)

‘09 1.00 0.92(0.82–1.03)

0.91(0.81–1.02)

1.00 0.95(0.85–1.06)

1.12(1.00–1.27)

1.00 0.77(0.70–0.84)

0.70(0.63–0.78)

1.00 1.01(0.94–1.10)

1.05(0.97–1.14)

‘10 1.00 0.81(0.74–0.89)

0.89(0.81–0.99)

1.00 0.98(0.85–1.12)

1.14(0.99–1.31)

1.00 0.84(0.75–0.93)

0.71(0.64–0.80)

1.00 1.06(0.98–1.14)

1.09(1.01–1.18)

‘11 1.00 0.92(0.83–1.01)

0.98(0.88–1.08)

1.00 0.93(0.83–1.05)

0.99(0.87–1.11)

1.00 0.87(0.79–0.96)

0.74(0.67–0.82)

1.00 1.04(0.97–1.12)

1.05(0.97–1.13)

SEP = socioeconomic position.a Values are odds ratios (95% confidence intervals) adjusted for age, sex, school type (middle school, general high school, vocational high school), region (metro city, small

city, rural area), body mass index, and exercise.b Values are odds ratios (95% confidence intervals) adjusted for age, school type (middle school, general high school, vocational high school), region (metro city, small city,

rural area), body mass index, and exercise.

K. Kim et al. / Appetite 71 (2013) 388–395 393

394 K. Kim et al. / Appetite 71 (2013) 388–395

the higher SEP group. A few studies based on the general Koreanpopulation found that some health policies, such as antismokingpolicies, ironically were likely to widen socioeconomic healthinequalities, suggesting the need for policies that are more pro-gressive and effectively delivered to disadvantaged social groups(Khang, Yun, Cho, & Jung-Choi, 2009; Ryu, 2010).

The change of unhealthy food intake among SEP groups overtime in this study appeared to be parallel to the recent trend ofoverweight over time by SEP level. According to several recentstudies, the low SEP was related to the increased risk of obesityamong adolescents (Kim, Lee, Choi, & Oh, 2011; Oh et al., 2011).The prevalence of obesity was higher in adolescents with highhousehold income than those with low household income in1998 (5.0% for the lowest quartile group vs 6.6% for the highestquartile group) but the prevalence of obesity increased in thelow SEP group and decreased in the high SEP group in 2007–2008 (9.7% for the lowest quartile group vs 5.5% for the highestquartile group) (Kim et al., 2011). The difference in overweightby SEP might be wider over time in that the dietary behaviors ofthe high SEP group underwent greater desirable changes than thelow SEP group. Therefore, continuous monitoring of dietary behav-ior patterns and health outcomes including obesity by SEP, and thefurther study on their relationship with effects of policies shouldbe required to avoid aggravating these inequalities in the future.

This study has several limitations. First, the policies on die-tary behaviors were not directed toward changes in individualbehaviors, but rather changes to the school food environment.Thus, unlike intervention programs for targeted populations,the effects of policies on behavioral changes remain unclear.The effects might be influenced by external variables, such asfamily and individual factors. However, evaluating effects of pol-icies from a long-term and strategic perspective is important toimprove dietary behaviors and health outcomes. Second, thisstudy used the FAS as a SEP indicator. Given that measurementof the income, education, or occupation of adolescents’ parentsas a SEP indicator might introduce bias due to of non-responsesand inaccurate reporting (Lien, Friestad, & Klepp, 2001; Wardleet al., 2004), the FAS was recently developed (Currie et al.,2008). Studies of the relationship between the FAS and dietarybehaviors in adolescents have shown the usefulness of FAS tomeasure adolescent’s SEP (Currie et al., 2008), and a recent Kor-ean study using KYRBS data also reported that it was applicableto measure SEP for Korean adolescents (Cho & Khang, 2010).Third, because the consumption of unhealthy foods was onlymeasured by the frequency consumption without taking into ac-count the amounts of foods, the intake results among SEP groupsmight have a substantial amount of measurement error in esti-mating energy intake. However, the trend of unhealthy foods in-takes by SEP through the years in this study was similar to thetrend of obesity by SEP so that we expect the measurement er-ror could be less likely to influence the results. Despite theselimitations, this study has some strength. This study tried toevaluate the effect of national nutritional policies focusing onthe regulation of unhealthy foods to adolescents using a nation-ally representative sample of Korean adolescents and further-more investigate the effect of the policies on socioeconomicdisparity in the unhealthy food intake.

In conclusion, this study found the positive effect of nutritionalpolicy on unhealthy food intake among adolescents regardless ofSEP, showing a decreased intake during the period in which nutri-tional policies restricting unhealthy foods were implemented.However, the difference of unhealthy food intakes by SEP and therisk of frequent consumption among SEP groups have changed be-fore and after implementation of the nutrition policies. Therefore,the persistent monitoring of the socioeconomic disparity state inundesirable food consumption and the effect of policy on the

disparity is necessary to avoid aggravating the inequalities in thefuture.

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