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A school-based intervention to promote dietary change
Journal of Adolescent Health 36 (2005) 529.e15–529.e22
Original article
A school-based intervention to promote dietary change Hillevi C. Prell, M.S.a,*, M. Christina Berg, Ph.D.a,b, Lena M. Jonsson, Ph.D.a, and Lauren Lissner, Ph.D.c a
Department of Home Economics, Göteborg University, Göteborg, Sweden b Cardiovascular Institute, Göteborg University, Göteborg, Sweden c Department of Primary Health Care, Sahlgrenska Academy at Göteborg University and Nordic School of Public Health, Göteborg, Sweden Manuscript received November 21, 2003; manuscript accepted August 14, 2004
Abstract
Purpose: This study examined the effect of 2 school-based interventions on adolescents’ consumption and knowledge of fish with the hypothesis that home economics education would enhance the effect of modifications in the school canteen. The school lunch intervention (SL) focused on changes in the school canteen, and the school lunch ⫹ home economics intervention (SL ⫹ HE) in addition consisted of changes in the home economics syllabus. Pupils in the 8th grade (n ⫽ 228) from 3 schools in Göteborg, Sweden, participated (control, n ⫽ 83; SL group, n ⫽ 58; SL ⫹ HE group, n ⫽ 87). Methods: A controlled design was used in which behavior and knowledge were assessed before and after the intervention. In contrast to much previous research of this type, measurement of behavior was based primarily on direct observation as opposed to self-reported intakes. Behavior (fish consumption) was measured individually by structured observations in the school canteen 5 times (once a week) when fish was served. Nutritional knowledge was measured by means of 10 items in a questionnaire. To analyze changes in behavior, a nonparametric statistical method assessing systematic change in paired ordered categoric variables was used. Results: At follow-up evaluation, consumption had increased significantly in the SL ⫹ HE group, a change that also differed from the control group. In addition, significant positive changes in knowledge were observed in both intervention groups, but not in controls. Conclusions: The results suggest that dietary change was achieved by modifying conditions in the school canteen together with changing the home economics syllabus. This study shows the importance of the school in the promotion of dietary change among adolescents. © 2005 Society for Adolescent Medicine. All rights reserved.
Keywords:
Health education; Food habits; Behavior; Dietary assessment; Knowledge; Adolescents; Home economics; School lunch; Fish
There is a growing interest in ways to influence food choice among children and adolescents because eating patterns that develop during those years are likely to be maintained and preserved into adulthood [1– 4]. Intervention programs that target health promotion and disease prevention may be most effective if introduced early. Indeed, as reported in a review of nutrition education studies [5], the
*Address correspondence to: Hillevi Prell, M.S., Department of Home Economics, Göteborg University, Box 300, 405 30 Göteborg, Sweden. E-mail address: [email protected]
majority of school-based nutrition education interventions focused on younger children. However, a recent study suggested that food habits change significantly during adolescence [6], and that health promotion during the adolescent years therefore ought to be encouraged. Working with adolescents may offer unique challenges, and more research is needed in this area [7]. In the Swedish National Aims and Strategies for Nutrition 1999 –2004 [8], it is recommended that the intake of fruits, vegetables, grain products, and fish should increase, whereas the intake of fat should decrease. For the past 2 or
1054-139X/05/$ – see front matter © 2005 Society for Adolescent Medicine. All rights reserved. doi:10.1016/j.jadohealth.2004.08.009
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3 decades, much research has focused on decreasing fat intake and increasing fruit and vegetable intake, whereas there is a paucity of studies focusing on how to increase the intake of fish. Although fish always has been an important part of the Swedish cuisine, many young people have negative attitudes toward fish [9,10], and school children in Sweden have been reported to have low consumption of fish, compared with the whole population [11]. Fish can be a valuable source of vitamin D and selenium, as well as contributing to the intake of zinc and iron, all of which have been reported to be low in dietary surveys of adolescents [12,13]. Furthermore, polyunsaturated fatty acids in fish can help to improve the quality of fat in the diet, compared with currently high proportions of saturated fatty acids reported in diets of Swedish adolescents [12]. Moreover, about 5% of young Swedes eat a vegetarian lunch at school [14], and fish could be an alternative for some individuals who refrain from eating meat for ethical reasons. Thus, there are a number of potential reasons for promoting fish consumption in young Swedes. Schools may provide a natural arena for health promotion in children and adolescents [5,15–18]. Appropriate behavioral theory and prior research, focusing on specific food-related behaviors and clearly setting behavior change as a goal, have guided the most successful programs. For behavior change to occur and persist, interventions must create and maintain school environments that support healthful behavior [4,16]. For instance, it is important that the school canteen promotes as well as serves healthy alternatives. In Sweden, all children of compulsory school age are entitled to free school lunches, which makes the school canteen a suitable context for studies oriented toward children’s eating habits. The free school lunch usually consists only of 1 hot dish (in some cases 2), with salad as a side dish and crisp bread. However, modification of school lunches alone has been shown to have minimal effects on behavior, whereas the combination of school meal modifications and classroom education are proposed to have positive effects [5,16]. The present study examined the effectiveness of 2 interventions aimed at increasing adolescents’ intake of fish in school. We compared the effect of school lunch modifications alone (SL) and school lunch modification plus modification of the home economics syllabus (SL ⫹ HE). Methods Research design Our hypothesis was that changes within the home economics syllabus together with relevant changes in the school canteen would have positive effects on pupils’ fish consumption. Two interventions, the SL, SL ⫹ HE, and a control group were compared to evaluate the effectiveness of school canteen changes and home economics in increas-
Randomization of control and intervention condition
Control school 5 classes n=131
Intervention school 1
Intervention school 2
2 classes n=55
2 classes n=58
2 classes n=60
3 classes n=86
Control n=131
SLa n=113c
SL+HEb n=146c
Participantsd n=83
Participantsd n=58
Participantsd n=87
a
SL=school lunch intervention SL+HE=school lunch+home economics intervention Number subject to interventions. d Number participating in at least 3 measures at pre-intervention and 3 measures at postintervention (SL: n=29 from school 1 and n=29 from school 2; SL+HE: n=47 from school 1 and n=40 from school 2). b c
Fig. 1. Diagram showing the study including randomization, interventions, number of schools, classes, and number of participants in each group.
ing fish consumption. The study was conducted among all 8th grade pupils (age, ⯝14 y) at 3 comprehensive schools (n ⫽ 390; 47% girls and 53% boys) in the Göteborg area in Sweden. The schools were selected to be similar regarding number of pupils, socioeconomic characteristics, kitchen facilities, serving systems, and willingness of school foodservice personnel and home-economics teachers to engage in the study. All 8th grade pupils at the 3 schools were enrolled in home economics during the terms the study took place. The schools were assigned randomly to control or intervention conditions. An outline of the study design and number of participants in each group is shown in Figure 1. At both intervention schools, all 8th graders were subject to changes in the school canteen regarding fish, whereas 2 classes from one school and 3 classes from the other school also were subject to changes within the home economics syllabus (more focus on fish). The classes were assigned to either intervention condition based on convenience, without awareness of the identity of the pupils. In the 3 schools, the pupils were informed that a study about fish consumption in the school canteen was going to take place, which included a questionnaire and a consumption study, and participation was voluntary. However, no details of the home economics intervention were provided. A controlled intervention design was used in which measurements took place both before and after the interventions in all 3 groups (SL, SL ⫹ HE, and control). Altogether, 228 pupils (58%) were present at both baseline and follow-up dietary assessment, including 83 pupils (63%) in the control group, 58 pupils (51%) in the SL group, and 87 pupils (60%) in the SL ⫹ HE group. The distribution of participants in control and intervention groups over a number of baseline characteristics is shown in Table 1. Although the number of boys and girls in the study population were
H.C. Prell et al. / Journal of Adolescent Health 36 (2005) 529.e15–529.e22 Table 1 Baseline characteristics of students completing both baseline and followup dietary assessment by control and intervention groups Outcome
Native country (%) Sweden Other than Sweden Gender (%) Boy Girl Total fish consumption (%) Noneater Taster Eater Total number of correct responses (mean)
Control n ⫽ 83*
SL n ⫽ 58*
SL ⫹ HE n ⫽ 87*
86 14
93 7
91 9
Differences between the groups NS
34 66
55 45
2 21 77
3 38 59
6 38 56
p ⬍ .05‡
3.2
2.8
3.8
study was performed during the school year of 1998 –1999. Respondents in the control school received both pre-test and post-test questionnaires and dietary assessment, but no intervention. The Research Ethics Committee at the University of Göteborg approved the study. Description of the interventions
p ⬍ .05† 49 51
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p ⬍ .05†
NOTE. n ⫽ 228. Differences between groups were tested with 2 and Kruskall-Wallis tests. NS, not significant. * Numbers might be somewhat lower due to missing values. † Differences were significant between SL and SL ⫹ HE. ‡ Differences were significant between control and SL ⫹ HE.
approximately equal, the proportions of participants were less balanced. For instance, there were almost twice as many girls as boys in the SL group. Furthermore, baseline knowledge about fish was higher in the SL ⫹ HE group compared with the SL group. The control group differed from the SL ⫹ HE group regarding fish consumption, with more eaters and fewer tasters and noneaters in the control group. At both baseline and follow-up evaluation the pupils completed a questionnaire assessing knowledge about fish and selected background characteristics. At the same time, fish consumption was measured by structured observations in the school canteen setting. The dietary assessment started the week after the questionnaires had been distributed. The
The 2 interventions were developed from the results of a pilot study [19,20]. According to the results from the study, attitudes toward fish, friends’ behavior, and perceived control were important predictors of the intention to eat fish. Moreover, the result suggested that it is important to alter dishes so that they appeal to children and to pay attention to the whole meal, accompaniments included. It also may be important to convey to the pupils that the fish served is healthy and prepared with care. Both interventions consisted of modifications of the school lunch, and additional modifications within the home economics syllabus were made in the SL ⫹ HE group so that more lessons dealt with fish-related issues (i.e., the total number of home economics lessons were constant in both intervention groups). Components of the interventions are shown in Table 2. The SL intervention focused on the preparation and appearance of the fish meals, on extending the choice, and on marketing. The pupils also had the opportunity to influence the fish selection by voting for 1 fish dish (of 10 suggested by the children themselves) that they would like to have. The winning dish was served on the ordinary fish days 1 time during the intervention period and 1 time during the posttest dietary assessment. The classroom component of the SL ⫹ HE group consisted of lessons about fish and nutrition and classroom cooking experiences. To show the care that the personnel put into preparing the fish, slides taken in the school canteen kitchen, with the school food-service personnel preparing fish, were shown to the pupils. Showing slides from the work in the school lunch kitchen could be one approach toward decreasing the distance between the school canteen kitchen and the customer.
Table 2 Major components of the interventions SL component
HE component
Personnel took part in a 1-day training session in preparing fish Alternative dish always was served: either smoked mackerel or pickled herring Dishes were garnished attractively with lemon, dill, or parsley Accompaniments were improved Two sauces to choose from instead of one Freshly boiled potatoes A ready-made portion of the fish meal was shown to the pupils The school lunchroom was decorated with fish-related objects The students voted for a fish dish to be served at intervention and at follow-up evaluation (i.e., on an ordinary fish day)
5 classroom cooking experiences focusing on fish instead of the usual 3 One cooking experience was devoted to the fish dish that the pupils voted for One lesson about nutrition and fish One lesson when a fish retailer discussed different fish species and how to fillet them Slides about cooking fish in the school lunchroom kitchen were shown to the pupils Each pupil selected a fish-related topic and wrote a short paper about it
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Table 3 Percent correct responses on each knowledge item at baseline and follow-up evaluation in control and intervention groups Control n ⫽ 83*
SL ⫹ HE n ⫽ 87*
SL n ⫽ 58*
Item
Baseline
Follow-up
Baseline
Follow-up
Baseline
Follow-up
The fat in fish is good for the heart Fish is rich in dietary fiber Sea fish is a good source of iodine Fatty fish contains more unsaturated fat than meat Fatty fish is, for example, salmon and mackerel Fish is an important source of selenium Fish contains healthy fat Fatty fish is a good source of vitamin D Vitamin D helps to build up the skeleton Saturated fat is healthier than unsaturated fat Total number of correct responses (mean)
36 1 41 23 28 35 67 29 48 11 3.2
44 4 36 35 43 32 60 32 1 10 3.4
30 5 25 28 34 30 53 35 44 4 2.8
48† 7 32 42 58† 33 68† 37 57 25‡ 4.1§
48 2 40 38 47 38 72 34 58 4 3.8
69‡ 7 48 52 64‡ 36 77 45* 55 27§ 4.8§
NOTE. Differences between baseline and follow-up evaluation were tested by the McNemar test and the Wilcoxon signed-rank test. * Numbers might be somewhat lower owing to missing values. † p ⬍ .05 ‡ p ⬍ .01 § p ⬍ .001
Behavior
Knowledge
Actual behavior (consumption of fish) was measured individually by structured observations in the school canteen 5 times (once a week) when fish was served. One person observed the selected fish component on each of the pupils’ plates and the other person observed the plate waste. Each observer had sample plates with weighed portion sizes to compare visually with portion size on the pupils’ plates. The size of a portion was determined on the basis of normal portions recommended by the Swedish National Food Administration [21]. The dietary assessment aimed at categorizing the pupils as noneaters, tasters, or eaters of fish. To be an eater one must have eaten more than half of a portion at least 3 of the 5 times the measurement took place; and to be a taster one must have taken part of the serving, not exceeding half, at least once. Nonparticipants included pupils who, on 3 of the 5 measurement occasions, reported ill, did not appear at the canteen, or if data on either taken portion or leftovers were missing.
Knowledge about fish was measured by 10 items, each with a 7-grade response scale (definitely no– definitely yes). See Table 3 for a summary of knowledge items. All methods used in the intervention study were pretested in the pilot study and when judged necessary were modified to improve reliability [20]. Statistical analysis
2 and Kruskall-Wallis tests were performed on baseline data to analyze differences between the control and experimental groups. To evaluate behavior change a nonparametric statistical method developed by Svensson [22] was used. This method has been described previously in studies examining food choices by children [23,24] and is considered appropriate for all types of ordered data without assumptions regarding the distributions. The method distinguishes systematic differences between paired ordered categoric assessments from the random component of variability.
Table 4 Systematic disagreement in position (RP) between baseline and follow-up evaluation for total behavior (fish consumption) and by gender in the control and intervention groups
Total group Boys Girls
n RP (CI)* n RP (CI)* n RP (CI)*
* CI, 95% confidence interval.
Control
SL
SL ⫹ HE
83 ⫺.08 (⫺.17 to .01) 41 ⫺.09 (⫺.22 to 0.03) 42 ⫺.07 (⫺.20 to .05)
58 .10 (⫺.02 to .22) 20 .05 (⫺.17 to .27) 38 .12 (⫺.03 to .28)
87 .15 (.06 to .24) 48 .17 (⫺.35 to .69) 39 .12 (⫺.03 to .27)
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Systematic disagreement between baseline and follow-up evaluation is shown by plotting the 2 sets (baseline and follow-up) of cumulative relative frequencies of categories regarding behavior (fish consumption). It is visually easy to determine from the shape of the relative/receiver operating characteristic (ROC) curve the extent and location of any systematic disagreements in categories (i.e., noneater, taster, and eater). Total agreement means that there is no systematic change between baseline and follow-up data and the ROC curve will be located on the diagonal of identical coordinates. Increased fish consumption at follow-up evaluation will result in a ROC curve that deviates below the diagonal of agreement and a decreased consumption will result in a curve above the diagonal. This is a sign of systematic disagreement in position, which is expressed by a measure called relative position (RP). A RP could take values between ⫺1 and 1. Values close to 0 indicate a lack of systematic disagreement between baseline and follow-up data and a positive RP value indicates an increase in consumption. To create 95% confidence intervals, the standard error of the RP measure were estimated by using the socalled jack-knife technique. Behavioral changes also were analyzed separately for girls and boys. The knowledge items were dichotomized: 0 ⫽ wrong answer or do not know. For each item, the difference between baseline and follow-up evaluation were analyzed by the McNemar test. The total number of correct responses then was summed across the 10 items, after which the difference between baseline and follow-up evaluation were tested using the Wilcoxon signed-rank test. To detect differences regarding change in knowledge between the groups (control, SL, and SL ⫹ HE), the Mann-Whitney U test was used. Likewise, gender differences regarding knowledge were examined.
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Fig. 2. ROC curves for agreement regarding categories of behavior (fish consumption) at baseline and follow-up evaluation for control, SL intervention, and SL ⫹ HE intervention.
The observed behavioral changes from baseline to the follow-up period in the control and intervention groups are shown by ROC curves (Figure 2). The coordinates of the curves indicate the cumulative percentages of noneaters, tasters, and eaters for baseline and the follow-up period in the 3 groups. For the intervention groups the ROC curves are located to the lower side of the diagonal of total agreement, indicating that the number of noneaters and tasters decreased from baseline to follow-up evaluation. In the SL ⫹ HE group, the proportion of eaters at baseline increased from 56% to 71% at follow-up evaluation. In the SL group there was an increase from 59% to 69%, and in the control group there was a decrease from 77% to 69%. Changes in knowledge
Results Changes in behavior The systematic disagreement in position (RP) for the 3 conditions (control, SL, and SL ⫹ HE) regarding behavior is shown in Table 4. A systematic difference between baseline and follow-up information was evident regarding the behavior of pupils in the SL ⫹ HE group, meaning that participants were more inclined to taste and/or eat the fish after the intervention compared with before (i.e., the 95% confidence interval did not include 0). The behavioral change in the SL ⫹ HE group differed significantly from the control group (i.e., the confidence interval of the SL ⫹ HE group did not overlap the confidence interval of the control group). The change in fish consumption from baseline to the follow-up period for the SL group was similar to that observed in the SL ⫹ HE group, but neither statistically significant nor different from control. However, the SL ⫹ HE group did not differ significantly from the SL group.
Changes between baseline and follow-up evaluation for each knowledge item (percent correct responses) and for total number of correct responses in the 3 groups are shown in Table 4. In both intervention groups, significant changes in percent correct responses were observed regarding 4 knowledge items. The level of significance in the SL ⫹ HE group was stronger for all items except one. Regarding the total number of correct responses, changes between baseline and follow-up evaluation were significant in both intervention groups, and those group changes also differed from the control group. Gender aspects Gender differences regarding baseline behavior were noted. There were 4% noneaters, 20% tasters, and 76% eaters among the boys at baseline. For girls, the distribution was 4% noneaters, 42% tasters, and 54% eaters. The difference between girls and boys was significant (p ⬍ .01). Regarding baseline knowledge there were no gender differ-
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ences and no significant gender differences in changes in knowledge (data not shown). As is indicated by the confidence intervals in Table 3, no significant gender differences could be detected regarding behavioral changes in the 3 groups. However, visual inspection of the RP values suggested that boys (RP ⫽ .17) might have benefited somewhat more than girls (RP ⫽ .12) might have from the innovation in the home economics syllabus. Discussion Changes in behavior The present study examined the effectiveness of 2 interventions involving both the school canteen and home economics classes in influencing fish consumption in school in 8th grade pupils. Because the hypothesis was that home economics instruction would enhance the effect of changes in the school canteen, the main intervention (SL ⫹ HE) was based on modifications of the home economics syllabus together with modifications of the school lunch. This approach worked well and resulted in significantly more fish eaters at follow-up evaluation in the SL ⫹ HE group. In addition, this behavioral change in the SL ⫹ HE group differed significantly from the control group. School canteen changes only (SL group), did not result in any significant behavioral changes, but a similar tendency was present and the SL ⫹ HE group was not significantly better than the SL group. Changes in knowledge Significant increases in pupils’ knowledge about fish (compared with control) were detected in both the SL and the SL ⫹ HE group. We expected knowledge to be affected in all 3 groups because all pupils had been enrolled in home economics for the entire term. We also expected increases to be greater in the SL ⫹ HE group than in the SL group, but this was not the case. The fact that changes were similar in both groups might be explained by an overall heightened awareness of fish. The increased focus on fish in the school canteen may have facilitated the acquisition of knowledge for all pupils. Moreover, the same home economics teachers were engaged in home economics instruction in the 2 groups at each intervention school. Thus, it is possible that pupils in the SL group were subject to a “spill-over” effect. The teachers may have become more enthusiastic as the intervention went on and transmitted this to all pupils, a factor for which we could not control. However, the use of 2 schools, in which half of the pupils also received additional home economics instruction, also is considered to be a strength in this study. In this way, conditions in the school canteen were the same for half of the pupils in each intervention group and one might assume that the observed behavioral changes in the SL ⫹ HE group were not only a result of the environmental conditions in the school canteen.
Explanations for outcome A possible reason for the success of the achieved behavioral changes could be the implementation of current recommendations, which include, among other things, addressing a highly specific behavior, setting behavior change as a goal, and using behavioral theory and prior research in developing the interventions [5,15,16]. As mentioned earlier, the content of the interventions was developed based on research performed in a pilot study in which the Theory of Planned Behavior was used [19,20]. Prior research has shown that this model is suitable for understanding factors influencing food choice in both children and adolescents [25–27] and that it can be useful in suggesting the content of interventions [5,28]. Also, in line with what was concluded in a recent review of nutrition education intervention research [29], much effort was put into developing appropriate evaluation instruments and assessing reliability in the pilot study. Besides knowledge about nutrition and fish, the concept of care was stressed in the SL ⫹ HE group by showing slides and telling about the work performed in the school canteen kitchen. The pupils also had the chance to experience the skills of a fish retailer filleting different fish species and explaining how to distinguish them from each other. Above all, the pupils in the SL ⫹ HE group were engaged in more cooking classes than the pupils in the SL group. Practical, hands-on experience with diverse foods has been found to increase dietary acceptance of the same foods when they were offered at the school lunch [30]. In another study, actual cooking experiences and eating food with peers accompanied by classroom instruction provided a promising approach to nutrition education [31]. It was shown in the pilot study [20] that what other people did (i.e., that the pupils’ friends also ate the fish) was more important than other people’s (e.g., parents’) opinion about fish consumption in the school canteen. Pupils influence and learn from each other when eating lunch at the school and, perhaps more importantly, by cooking similar foods during home economics classes that had been offered in the school canteen and eating together in a class environment. Methodologic considerations The dietary assessment was developed in the pilot study and consisted of structured observations of pupils’ intake and plate waste in the school canteen setting. One of the major strengths of this research was that behavior was measured objectively. Indeed, it has been recommended that future work should concentrate on developing appropriate dietary assessment tools for children [5,15]. Many dietary intervention studies rely on pupils’ self-reported behavior, which may be subject to reporting bias including social desirability bias. According to group discussions with pupils in the pilot study, the pupils claimed that their consumption was not affected by being observed. Furthermore,
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the presence of a control group, in which consumption of fish actually decreased during the period, supports the notion that any possible observer bias was negligible. A number of other design features were not optimal and limited the conclusions that could be drawn. For instance, baseline differences between groups might have influenced the result. Specifically, more pupils in the control group were fish eaters, which means that the potential to change were somewhat lower in that group. Also, because there were significantly more fish eaters among the boys, their readiness to change was lower compared with the girls. The drop-out rates in the intervention and control groups also may be noted (Figure 1). However, when broadening the inclusion criteria to use data from all pupils who attended the cafeteria at least once in the preintervention and once in the postintervention periods, a higher participation rate of 85% could be obtained. By using this more complete sample, the results were similar to those observed with the more stringent attendance criteria. However, it was not the aim of the present study to make pupils who were not interested in having school lunch come to the school canteen, but to try to influence those who already went there. It is most likely that other measures, apart from those that were applied in this study, will have to be taken to convince resistant pupils to come to the school canteen. Another limitation was that we did not use a factorial design (i.e., that one group was assigned to a home economics intervention only). It would have been desirable to examine the impact of home economics alone on eating behavior as has been recognized by others [15], but for various reasons (time limits and financial constraints) this was not practicable. Further work needs to be performed to work out the independent effects of interventions in the school canteen and home economics, respectively. Thus, it is recommended that future intervention studies use a design that makes it possible to assess single effects as well as combined effects. Finally, the intervention was of a relatively short duration. Although fish intake patterns in the school canteen were influenced during this time, we do not know whether the effects were long lasting. Conclusions We have shown in the present study that it is possible to influence adolescents’ consumption of fish by combining modifications of the school lunch with modifications of the home economics syllabus (SL ⫹ HE). The addition of an improved home economics component to environmental changes in the school canteen significantly influenced dietary behavior. The largest absolute changes were seen with the SL ⫹ HE intervention, although suggestive improvements could be observed even in the SL intervention. These results imply that home economics as well as the school canteen both are potentially important components in the promotion of healthy diets among adolescents.
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application of the Theory of Planned Behaviour. Appetite 2000;34:5–19. Gummeson L, Jonsson I, Conner M. Predicting intentions and behaviour of Swedish 10 –16-year-olds at breakfast. Food Qual Prefer 1997;8:297–306. Dennison CM, Shepherd R. Adolescent food choice: an application of the Theory of Planned Behaviour. J Hum Nutr Diet 1995;8:9 –23. Bartholomew LK, Parcel GS, Kok G, Gottlieb NH. Intervention Mapping: Designing Theory- and Evidence-Based Health Promotion Programs. Mountain View: Mayfield Publishing Company, 2001. Contento IR, Randell JS, Basch CE. Review and analysis of evaluation measures used in nutrition education research. J Nutr Educ Behav 2002;34:2–25. Demas A. Food education in the classroom as a means of gaining acceptance of diverse, low-fat foods in the school lunch program. Doctoral dissertation (unpublished). Ithaca, NY: Cornell University, 1995. Liquori T, Koch PD, Contento IR, Castle J. The Cookshop Program: outcome evaluation of a nutrition education program linking lunchroom food experiences with classroom cooking experiences. J Nutr Educ 1998;30:302–13.
Original article
A school-based intervention to promote dietary change Hillevi C. Prell, M.S.a,*, M. Christina Berg, Ph.D.a,b, Lena M. Jonsson, Ph.D.a, and Lauren Lissner, Ph.D.c a
Department of Home Economics, Göteborg University, Göteborg, Sweden b Cardiovascular Institute, Göteborg University, Göteborg, Sweden c Department of Primary Health Care, Sahlgrenska Academy at Göteborg University and Nordic School of Public Health, Göteborg, Sweden Manuscript received November 21, 2003; manuscript accepted August 14, 2004
Abstract
Purpose: This study examined the effect of 2 school-based interventions on adolescents’ consumption and knowledge of fish with the hypothesis that home economics education would enhance the effect of modifications in the school canteen. The school lunch intervention (SL) focused on changes in the school canteen, and the school lunch ⫹ home economics intervention (SL ⫹ HE) in addition consisted of changes in the home economics syllabus. Pupils in the 8th grade (n ⫽ 228) from 3 schools in Göteborg, Sweden, participated (control, n ⫽ 83; SL group, n ⫽ 58; SL ⫹ HE group, n ⫽ 87). Methods: A controlled design was used in which behavior and knowledge were assessed before and after the intervention. In contrast to much previous research of this type, measurement of behavior was based primarily on direct observation as opposed to self-reported intakes. Behavior (fish consumption) was measured individually by structured observations in the school canteen 5 times (once a week) when fish was served. Nutritional knowledge was measured by means of 10 items in a questionnaire. To analyze changes in behavior, a nonparametric statistical method assessing systematic change in paired ordered categoric variables was used. Results: At follow-up evaluation, consumption had increased significantly in the SL ⫹ HE group, a change that also differed from the control group. In addition, significant positive changes in knowledge were observed in both intervention groups, but not in controls. Conclusions: The results suggest that dietary change was achieved by modifying conditions in the school canteen together with changing the home economics syllabus. This study shows the importance of the school in the promotion of dietary change among adolescents. © 2005 Society for Adolescent Medicine. All rights reserved.
Keywords:
Health education; Food habits; Behavior; Dietary assessment; Knowledge; Adolescents; Home economics; School lunch; Fish
There is a growing interest in ways to influence food choice among children and adolescents because eating patterns that develop during those years are likely to be maintained and preserved into adulthood [1– 4]. Intervention programs that target health promotion and disease prevention may be most effective if introduced early. Indeed, as reported in a review of nutrition education studies [5], the
*Address correspondence to: Hillevi Prell, M.S., Department of Home Economics, Göteborg University, Box 300, 405 30 Göteborg, Sweden. E-mail address: [email protected]
majority of school-based nutrition education interventions focused on younger children. However, a recent study suggested that food habits change significantly during adolescence [6], and that health promotion during the adolescent years therefore ought to be encouraged. Working with adolescents may offer unique challenges, and more research is needed in this area [7]. In the Swedish National Aims and Strategies for Nutrition 1999 –2004 [8], it is recommended that the intake of fruits, vegetables, grain products, and fish should increase, whereas the intake of fat should decrease. For the past 2 or
1054-139X/05/$ – see front matter © 2005 Society for Adolescent Medicine. All rights reserved. doi:10.1016/j.jadohealth.2004.08.009
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3 decades, much research has focused on decreasing fat intake and increasing fruit and vegetable intake, whereas there is a paucity of studies focusing on how to increase the intake of fish. Although fish always has been an important part of the Swedish cuisine, many young people have negative attitudes toward fish [9,10], and school children in Sweden have been reported to have low consumption of fish, compared with the whole population [11]. Fish can be a valuable source of vitamin D and selenium, as well as contributing to the intake of zinc and iron, all of which have been reported to be low in dietary surveys of adolescents [12,13]. Furthermore, polyunsaturated fatty acids in fish can help to improve the quality of fat in the diet, compared with currently high proportions of saturated fatty acids reported in diets of Swedish adolescents [12]. Moreover, about 5% of young Swedes eat a vegetarian lunch at school [14], and fish could be an alternative for some individuals who refrain from eating meat for ethical reasons. Thus, there are a number of potential reasons for promoting fish consumption in young Swedes. Schools may provide a natural arena for health promotion in children and adolescents [5,15–18]. Appropriate behavioral theory and prior research, focusing on specific food-related behaviors and clearly setting behavior change as a goal, have guided the most successful programs. For behavior change to occur and persist, interventions must create and maintain school environments that support healthful behavior [4,16]. For instance, it is important that the school canteen promotes as well as serves healthy alternatives. In Sweden, all children of compulsory school age are entitled to free school lunches, which makes the school canteen a suitable context for studies oriented toward children’s eating habits. The free school lunch usually consists only of 1 hot dish (in some cases 2), with salad as a side dish and crisp bread. However, modification of school lunches alone has been shown to have minimal effects on behavior, whereas the combination of school meal modifications and classroom education are proposed to have positive effects [5,16]. The present study examined the effectiveness of 2 interventions aimed at increasing adolescents’ intake of fish in school. We compared the effect of school lunch modifications alone (SL) and school lunch modification plus modification of the home economics syllabus (SL ⫹ HE). Methods Research design Our hypothesis was that changes within the home economics syllabus together with relevant changes in the school canteen would have positive effects on pupils’ fish consumption. Two interventions, the SL, SL ⫹ HE, and a control group were compared to evaluate the effectiveness of school canteen changes and home economics in increas-
Randomization of control and intervention condition
Control school 5 classes n=131
Intervention school 1
Intervention school 2
2 classes n=55
2 classes n=58
2 classes n=60
3 classes n=86
Control n=131
SLa n=113c
SL+HEb n=146c
Participantsd n=83
Participantsd n=58
Participantsd n=87
a
SL=school lunch intervention SL+HE=school lunch+home economics intervention Number subject to interventions. d Number participating in at least 3 measures at pre-intervention and 3 measures at postintervention (SL: n=29 from school 1 and n=29 from school 2; SL+HE: n=47 from school 1 and n=40 from school 2). b c
Fig. 1. Diagram showing the study including randomization, interventions, number of schools, classes, and number of participants in each group.
ing fish consumption. The study was conducted among all 8th grade pupils (age, ⯝14 y) at 3 comprehensive schools (n ⫽ 390; 47% girls and 53% boys) in the Göteborg area in Sweden. The schools were selected to be similar regarding number of pupils, socioeconomic characteristics, kitchen facilities, serving systems, and willingness of school foodservice personnel and home-economics teachers to engage in the study. All 8th grade pupils at the 3 schools were enrolled in home economics during the terms the study took place. The schools were assigned randomly to control or intervention conditions. An outline of the study design and number of participants in each group is shown in Figure 1. At both intervention schools, all 8th graders were subject to changes in the school canteen regarding fish, whereas 2 classes from one school and 3 classes from the other school also were subject to changes within the home economics syllabus (more focus on fish). The classes were assigned to either intervention condition based on convenience, without awareness of the identity of the pupils. In the 3 schools, the pupils were informed that a study about fish consumption in the school canteen was going to take place, which included a questionnaire and a consumption study, and participation was voluntary. However, no details of the home economics intervention were provided. A controlled intervention design was used in which measurements took place both before and after the interventions in all 3 groups (SL, SL ⫹ HE, and control). Altogether, 228 pupils (58%) were present at both baseline and follow-up dietary assessment, including 83 pupils (63%) in the control group, 58 pupils (51%) in the SL group, and 87 pupils (60%) in the SL ⫹ HE group. The distribution of participants in control and intervention groups over a number of baseline characteristics is shown in Table 1. Although the number of boys and girls in the study population were
H.C. Prell et al. / Journal of Adolescent Health 36 (2005) 529.e15–529.e22 Table 1 Baseline characteristics of students completing both baseline and followup dietary assessment by control and intervention groups Outcome
Native country (%) Sweden Other than Sweden Gender (%) Boy Girl Total fish consumption (%) Noneater Taster Eater Total number of correct responses (mean)
Control n ⫽ 83*
SL n ⫽ 58*
SL ⫹ HE n ⫽ 87*
86 14
93 7
91 9
Differences between the groups NS
34 66
55 45
2 21 77
3 38 59
6 38 56
p ⬍ .05‡
3.2
2.8
3.8
study was performed during the school year of 1998 –1999. Respondents in the control school received both pre-test and post-test questionnaires and dietary assessment, but no intervention. The Research Ethics Committee at the University of Göteborg approved the study. Description of the interventions
p ⬍ .05† 49 51
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p ⬍ .05†
NOTE. n ⫽ 228. Differences between groups were tested with 2 and Kruskall-Wallis tests. NS, not significant. * Numbers might be somewhat lower due to missing values. † Differences were significant between SL and SL ⫹ HE. ‡ Differences were significant between control and SL ⫹ HE.
approximately equal, the proportions of participants were less balanced. For instance, there were almost twice as many girls as boys in the SL group. Furthermore, baseline knowledge about fish was higher in the SL ⫹ HE group compared with the SL group. The control group differed from the SL ⫹ HE group regarding fish consumption, with more eaters and fewer tasters and noneaters in the control group. At both baseline and follow-up evaluation the pupils completed a questionnaire assessing knowledge about fish and selected background characteristics. At the same time, fish consumption was measured by structured observations in the school canteen setting. The dietary assessment started the week after the questionnaires had been distributed. The
The 2 interventions were developed from the results of a pilot study [19,20]. According to the results from the study, attitudes toward fish, friends’ behavior, and perceived control were important predictors of the intention to eat fish. Moreover, the result suggested that it is important to alter dishes so that they appeal to children and to pay attention to the whole meal, accompaniments included. It also may be important to convey to the pupils that the fish served is healthy and prepared with care. Both interventions consisted of modifications of the school lunch, and additional modifications within the home economics syllabus were made in the SL ⫹ HE group so that more lessons dealt with fish-related issues (i.e., the total number of home economics lessons were constant in both intervention groups). Components of the interventions are shown in Table 2. The SL intervention focused on the preparation and appearance of the fish meals, on extending the choice, and on marketing. The pupils also had the opportunity to influence the fish selection by voting for 1 fish dish (of 10 suggested by the children themselves) that they would like to have. The winning dish was served on the ordinary fish days 1 time during the intervention period and 1 time during the posttest dietary assessment. The classroom component of the SL ⫹ HE group consisted of lessons about fish and nutrition and classroom cooking experiences. To show the care that the personnel put into preparing the fish, slides taken in the school canteen kitchen, with the school food-service personnel preparing fish, were shown to the pupils. Showing slides from the work in the school lunch kitchen could be one approach toward decreasing the distance between the school canteen kitchen and the customer.
Table 2 Major components of the interventions SL component
HE component
Personnel took part in a 1-day training session in preparing fish Alternative dish always was served: either smoked mackerel or pickled herring Dishes were garnished attractively with lemon, dill, or parsley Accompaniments were improved Two sauces to choose from instead of one Freshly boiled potatoes A ready-made portion of the fish meal was shown to the pupils The school lunchroom was decorated with fish-related objects The students voted for a fish dish to be served at intervention and at follow-up evaluation (i.e., on an ordinary fish day)
5 classroom cooking experiences focusing on fish instead of the usual 3 One cooking experience was devoted to the fish dish that the pupils voted for One lesson about nutrition and fish One lesson when a fish retailer discussed different fish species and how to fillet them Slides about cooking fish in the school lunchroom kitchen were shown to the pupils Each pupil selected a fish-related topic and wrote a short paper about it
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Table 3 Percent correct responses on each knowledge item at baseline and follow-up evaluation in control and intervention groups Control n ⫽ 83*
SL ⫹ HE n ⫽ 87*
SL n ⫽ 58*
Item
Baseline
Follow-up
Baseline
Follow-up
Baseline
Follow-up
The fat in fish is good for the heart Fish is rich in dietary fiber Sea fish is a good source of iodine Fatty fish contains more unsaturated fat than meat Fatty fish is, for example, salmon and mackerel Fish is an important source of selenium Fish contains healthy fat Fatty fish is a good source of vitamin D Vitamin D helps to build up the skeleton Saturated fat is healthier than unsaturated fat Total number of correct responses (mean)
36 1 41 23 28 35 67 29 48 11 3.2
44 4 36 35 43 32 60 32 1 10 3.4
30 5 25 28 34 30 53 35 44 4 2.8
48† 7 32 42 58† 33 68† 37 57 25‡ 4.1§
48 2 40 38 47 38 72 34 58 4 3.8
69‡ 7 48 52 64‡ 36 77 45* 55 27§ 4.8§
NOTE. Differences between baseline and follow-up evaluation were tested by the McNemar test and the Wilcoxon signed-rank test. * Numbers might be somewhat lower owing to missing values. † p ⬍ .05 ‡ p ⬍ .01 § p ⬍ .001
Behavior
Knowledge
Actual behavior (consumption of fish) was measured individually by structured observations in the school canteen 5 times (once a week) when fish was served. One person observed the selected fish component on each of the pupils’ plates and the other person observed the plate waste. Each observer had sample plates with weighed portion sizes to compare visually with portion size on the pupils’ plates. The size of a portion was determined on the basis of normal portions recommended by the Swedish National Food Administration [21]. The dietary assessment aimed at categorizing the pupils as noneaters, tasters, or eaters of fish. To be an eater one must have eaten more than half of a portion at least 3 of the 5 times the measurement took place; and to be a taster one must have taken part of the serving, not exceeding half, at least once. Nonparticipants included pupils who, on 3 of the 5 measurement occasions, reported ill, did not appear at the canteen, or if data on either taken portion or leftovers were missing.
Knowledge about fish was measured by 10 items, each with a 7-grade response scale (definitely no– definitely yes). See Table 3 for a summary of knowledge items. All methods used in the intervention study were pretested in the pilot study and when judged necessary were modified to improve reliability [20]. Statistical analysis
2 and Kruskall-Wallis tests were performed on baseline data to analyze differences between the control and experimental groups. To evaluate behavior change a nonparametric statistical method developed by Svensson [22] was used. This method has been described previously in studies examining food choices by children [23,24] and is considered appropriate for all types of ordered data without assumptions regarding the distributions. The method distinguishes systematic differences between paired ordered categoric assessments from the random component of variability.
Table 4 Systematic disagreement in position (RP) between baseline and follow-up evaluation for total behavior (fish consumption) and by gender in the control and intervention groups
Total group Boys Girls
n RP (CI)* n RP (CI)* n RP (CI)*
* CI, 95% confidence interval.
Control
SL
SL ⫹ HE
83 ⫺.08 (⫺.17 to .01) 41 ⫺.09 (⫺.22 to 0.03) 42 ⫺.07 (⫺.20 to .05)
58 .10 (⫺.02 to .22) 20 .05 (⫺.17 to .27) 38 .12 (⫺.03 to .28)
87 .15 (.06 to .24) 48 .17 (⫺.35 to .69) 39 .12 (⫺.03 to .27)
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Systematic disagreement between baseline and follow-up evaluation is shown by plotting the 2 sets (baseline and follow-up) of cumulative relative frequencies of categories regarding behavior (fish consumption). It is visually easy to determine from the shape of the relative/receiver operating characteristic (ROC) curve the extent and location of any systematic disagreements in categories (i.e., noneater, taster, and eater). Total agreement means that there is no systematic change between baseline and follow-up data and the ROC curve will be located on the diagonal of identical coordinates. Increased fish consumption at follow-up evaluation will result in a ROC curve that deviates below the diagonal of agreement and a decreased consumption will result in a curve above the diagonal. This is a sign of systematic disagreement in position, which is expressed by a measure called relative position (RP). A RP could take values between ⫺1 and 1. Values close to 0 indicate a lack of systematic disagreement between baseline and follow-up data and a positive RP value indicates an increase in consumption. To create 95% confidence intervals, the standard error of the RP measure were estimated by using the socalled jack-knife technique. Behavioral changes also were analyzed separately for girls and boys. The knowledge items were dichotomized: 0 ⫽ wrong answer or do not know. For each item, the difference between baseline and follow-up evaluation were analyzed by the McNemar test. The total number of correct responses then was summed across the 10 items, after which the difference between baseline and follow-up evaluation were tested using the Wilcoxon signed-rank test. To detect differences regarding change in knowledge between the groups (control, SL, and SL ⫹ HE), the Mann-Whitney U test was used. Likewise, gender differences regarding knowledge were examined.
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Fig. 2. ROC curves for agreement regarding categories of behavior (fish consumption) at baseline and follow-up evaluation for control, SL intervention, and SL ⫹ HE intervention.
The observed behavioral changes from baseline to the follow-up period in the control and intervention groups are shown by ROC curves (Figure 2). The coordinates of the curves indicate the cumulative percentages of noneaters, tasters, and eaters for baseline and the follow-up period in the 3 groups. For the intervention groups the ROC curves are located to the lower side of the diagonal of total agreement, indicating that the number of noneaters and tasters decreased from baseline to follow-up evaluation. In the SL ⫹ HE group, the proportion of eaters at baseline increased from 56% to 71% at follow-up evaluation. In the SL group there was an increase from 59% to 69%, and in the control group there was a decrease from 77% to 69%. Changes in knowledge
Results Changes in behavior The systematic disagreement in position (RP) for the 3 conditions (control, SL, and SL ⫹ HE) regarding behavior is shown in Table 4. A systematic difference between baseline and follow-up information was evident regarding the behavior of pupils in the SL ⫹ HE group, meaning that participants were more inclined to taste and/or eat the fish after the intervention compared with before (i.e., the 95% confidence interval did not include 0). The behavioral change in the SL ⫹ HE group differed significantly from the control group (i.e., the confidence interval of the SL ⫹ HE group did not overlap the confidence interval of the control group). The change in fish consumption from baseline to the follow-up period for the SL group was similar to that observed in the SL ⫹ HE group, but neither statistically significant nor different from control. However, the SL ⫹ HE group did not differ significantly from the SL group.
Changes between baseline and follow-up evaluation for each knowledge item (percent correct responses) and for total number of correct responses in the 3 groups are shown in Table 4. In both intervention groups, significant changes in percent correct responses were observed regarding 4 knowledge items. The level of significance in the SL ⫹ HE group was stronger for all items except one. Regarding the total number of correct responses, changes between baseline and follow-up evaluation were significant in both intervention groups, and those group changes also differed from the control group. Gender aspects Gender differences regarding baseline behavior were noted. There were 4% noneaters, 20% tasters, and 76% eaters among the boys at baseline. For girls, the distribution was 4% noneaters, 42% tasters, and 54% eaters. The difference between girls and boys was significant (p ⬍ .01). Regarding baseline knowledge there were no gender differ-
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ences and no significant gender differences in changes in knowledge (data not shown). As is indicated by the confidence intervals in Table 3, no significant gender differences could be detected regarding behavioral changes in the 3 groups. However, visual inspection of the RP values suggested that boys (RP ⫽ .17) might have benefited somewhat more than girls (RP ⫽ .12) might have from the innovation in the home economics syllabus. Discussion Changes in behavior The present study examined the effectiveness of 2 interventions involving both the school canteen and home economics classes in influencing fish consumption in school in 8th grade pupils. Because the hypothesis was that home economics instruction would enhance the effect of changes in the school canteen, the main intervention (SL ⫹ HE) was based on modifications of the home economics syllabus together with modifications of the school lunch. This approach worked well and resulted in significantly more fish eaters at follow-up evaluation in the SL ⫹ HE group. In addition, this behavioral change in the SL ⫹ HE group differed significantly from the control group. School canteen changes only (SL group), did not result in any significant behavioral changes, but a similar tendency was present and the SL ⫹ HE group was not significantly better than the SL group. Changes in knowledge Significant increases in pupils’ knowledge about fish (compared with control) were detected in both the SL and the SL ⫹ HE group. We expected knowledge to be affected in all 3 groups because all pupils had been enrolled in home economics for the entire term. We also expected increases to be greater in the SL ⫹ HE group than in the SL group, but this was not the case. The fact that changes were similar in both groups might be explained by an overall heightened awareness of fish. The increased focus on fish in the school canteen may have facilitated the acquisition of knowledge for all pupils. Moreover, the same home economics teachers were engaged in home economics instruction in the 2 groups at each intervention school. Thus, it is possible that pupils in the SL group were subject to a “spill-over” effect. The teachers may have become more enthusiastic as the intervention went on and transmitted this to all pupils, a factor for which we could not control. However, the use of 2 schools, in which half of the pupils also received additional home economics instruction, also is considered to be a strength in this study. In this way, conditions in the school canteen were the same for half of the pupils in each intervention group and one might assume that the observed behavioral changes in the SL ⫹ HE group were not only a result of the environmental conditions in the school canteen.
Explanations for outcome A possible reason for the success of the achieved behavioral changes could be the implementation of current recommendations, which include, among other things, addressing a highly specific behavior, setting behavior change as a goal, and using behavioral theory and prior research in developing the interventions [5,15,16]. As mentioned earlier, the content of the interventions was developed based on research performed in a pilot study in which the Theory of Planned Behavior was used [19,20]. Prior research has shown that this model is suitable for understanding factors influencing food choice in both children and adolescents [25–27] and that it can be useful in suggesting the content of interventions [5,28]. Also, in line with what was concluded in a recent review of nutrition education intervention research [29], much effort was put into developing appropriate evaluation instruments and assessing reliability in the pilot study. Besides knowledge about nutrition and fish, the concept of care was stressed in the SL ⫹ HE group by showing slides and telling about the work performed in the school canteen kitchen. The pupils also had the chance to experience the skills of a fish retailer filleting different fish species and explaining how to distinguish them from each other. Above all, the pupils in the SL ⫹ HE group were engaged in more cooking classes than the pupils in the SL group. Practical, hands-on experience with diverse foods has been found to increase dietary acceptance of the same foods when they were offered at the school lunch [30]. In another study, actual cooking experiences and eating food with peers accompanied by classroom instruction provided a promising approach to nutrition education [31]. It was shown in the pilot study [20] that what other people did (i.e., that the pupils’ friends also ate the fish) was more important than other people’s (e.g., parents’) opinion about fish consumption in the school canteen. Pupils influence and learn from each other when eating lunch at the school and, perhaps more importantly, by cooking similar foods during home economics classes that had been offered in the school canteen and eating together in a class environment. Methodologic considerations The dietary assessment was developed in the pilot study and consisted of structured observations of pupils’ intake and plate waste in the school canteen setting. One of the major strengths of this research was that behavior was measured objectively. Indeed, it has been recommended that future work should concentrate on developing appropriate dietary assessment tools for children [5,15]. Many dietary intervention studies rely on pupils’ self-reported behavior, which may be subject to reporting bias including social desirability bias. According to group discussions with pupils in the pilot study, the pupils claimed that their consumption was not affected by being observed. Furthermore,
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the presence of a control group, in which consumption of fish actually decreased during the period, supports the notion that any possible observer bias was negligible. A number of other design features were not optimal and limited the conclusions that could be drawn. For instance, baseline differences between groups might have influenced the result. Specifically, more pupils in the control group were fish eaters, which means that the potential to change were somewhat lower in that group. Also, because there were significantly more fish eaters among the boys, their readiness to change was lower compared with the girls. The drop-out rates in the intervention and control groups also may be noted (Figure 1). However, when broadening the inclusion criteria to use data from all pupils who attended the cafeteria at least once in the preintervention and once in the postintervention periods, a higher participation rate of 85% could be obtained. By using this more complete sample, the results were similar to those observed with the more stringent attendance criteria. However, it was not the aim of the present study to make pupils who were not interested in having school lunch come to the school canteen, but to try to influence those who already went there. It is most likely that other measures, apart from those that were applied in this study, will have to be taken to convince resistant pupils to come to the school canteen. Another limitation was that we did not use a factorial design (i.e., that one group was assigned to a home economics intervention only). It would have been desirable to examine the impact of home economics alone on eating behavior as has been recognized by others [15], but for various reasons (time limits and financial constraints) this was not practicable. Further work needs to be performed to work out the independent effects of interventions in the school canteen and home economics, respectively. Thus, it is recommended that future intervention studies use a design that makes it possible to assess single effects as well as combined effects. Finally, the intervention was of a relatively short duration. Although fish intake patterns in the school canteen were influenced during this time, we do not know whether the effects were long lasting. Conclusions We have shown in the present study that it is possible to influence adolescents’ consumption of fish by combining modifications of the school lunch with modifications of the home economics syllabus (SL ⫹ HE). The addition of an improved home economics component to environmental changes in the school canteen significantly influenced dietary behavior. The largest absolute changes were seen with the SL ⫹ HE intervention, although suggestive improvements could be observed even in the SL intervention. These results imply that home economics as well as the school canteen both are potentially important components in the promotion of healthy diets among adolescents.
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