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Eating behaviour among undergraduate students. Comparing nutrition students with other courses
Appetite 84 (2014) 28–33
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Research report
Eating behaviour among undergraduate students. Comparing nutrition students with other courses ☆ Rui Poínhos a,*, Diogo Alves, Elisée Vieira, Sílvia Pinhão a,b, Bruno M.P.M. Oliveira a,c, Flora Correia a,b,d a
Faculdade de Ciências da Nutrição e Alimentação, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal Centro Hospitalar de São João, E.P.E., Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal c Laboratório de Inteligência Artificial e Apoio à Decisão, Instituto de Engenharia de Sistemas e Computadores, Tecnologia e Ciência, Rua Dr. Roberto Frias, 378, 4200-465 Porto, Portugal d Unidade de Investigação e Desenvolvimento de Nefrologia, Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal b
A R T I C L E
I N F O
Article history: Received 6 August 2014 Received in revised form 9 September 2014 Accepted 13 September 2014 Available online 21 September 2014 Keywords: Eating behaviour Nutrition students Higher education students Body mass index
A B S T R A C T
Our main aim was to compare eating behaviour between Portuguese undergraduate nutrition students and students attending other courses. Several eating behaviour dimensions were compared between 154 nutrition students and 263 students from other areas. Emotional and external eating were assessed by the Dutch Eating Behavior Questionnaire, dietary restraint was measured using the flexible and rigid control of eating behaviour subscales, binge eating was measured using the Binge Eating Scale, and eating selfefficacy using the General Eating Self-Efficacy Scale. Higher levels of flexible and rigid control were found in nutrition students from both sexes when compared to students from other courses. Female nutrition students also presented higher binge eating levels than their colleagues from other courses. To our knowledge no other work has previously assessed all eating behaviour dimensions considered in the current study among nutrition students. Besides the results by themselves, the data obtained from this study provide several clues to further studies to be developed regarding the still rarely approached issue of eating behaviour among nutrition students. © 2014 Elsevier Ltd. All rights reserved.
Introduction Several studies suggest that eating disorders or the risk for disordered eating behaviour are more prevalent in dietetic or nutrition students when compared with students from other courses (Drake, 1989; Fiates & Salles, 2001; Gonidakis et al., 2009; Kolka & Abayomi, 2012; Laus, Moreira, & Costa, 2009; Reinstein et al., 1992; Worobey & Schoenfeld, 1999). In some studies, although the differences were not significant, the results suggest a higher prevalence of risk of eating disorders among nutrition students (Dos Santos, Meneguci, & De Mendonça, 2008; Fredenberg, Berglund, & Dieken, 1996; Stipp & de Oliveira, 2003). Nevertheless, results from other studies suggest
☆ Acknowledgements: This work is part-funded by the ERDF – European Regional Development Fund through the COMPETE Programme (operational programme for competitiveness) and by National Funds through the FCT – Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) within projects PTDC/MAT/121107/2010 and FCOMP – 01-0124-FEDER-037281. The funders had no role in the design, analysis or writing of this article. * Corresponding author. E-mail address: [email protected] (R. Poínhos).
http://dx.doi.org/10.1016/j.appet.2014.09.011 0195-6663/© 2014 Elsevier Ltd. All rights reserved.
that nutrition and dietetic students are not different regarding disordered eating behaviour from other courses (Johnston & Christopher, 1991; Kiziltan & Karabudak, 2008; Mealha et al., 2013; Swezda & Thorne, 2002) or groups (Torresani, 2003) or even that nutrition students have lower risk of disordered eating behaviour when compared to pre-med students (Mehr et al., 2005). Even considering data indicating that students of nutrition and dietetics present a higher prevalence of eating disorder behaviour, the causal relationship still remains unknown (Korinth, Schiess, & Westenhoefer, 2009; Morgan, Vecchiatti, & Negrão, 2002). While some authors suggest that the selection of a nutrition or dietetics course is influenced by own personal experiences regarding food and weight control (Drake, 1989; Hughes & Desbrow, 2005; Magalhães & Motta, 2012; McArthur, 1995) or by a prior tendency to those behaviours (Stipp & de Oliveira, 2003), others suggest that the contact with food issues and the belief that a good appearance will be important for future professional success may be favourable to a higher incidence of eating disorders in nutrition students (Fiates & Salles, 2001; Penz, Dal Bosco, & Vieira, 2008). Despite the recognition of its importance (Drummond & Hare, 2012; Houston, Bassler, & Anderson, 2008; Korinth et al., 2009),studies focusing on eating behaviour among nutrition and
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dietetics students and professionals mostly study the prevalence or risk of eating disorders, and few evaluate eating behaviour dimensions. For instance, both emotional and external eating are eating behaviour dimensions associated with overeating, weight gain and higher body mass index (BMI; Elfhag & Linné, 2005; Koenders & Van Strien, 2011; Van Strien, Herman, & Verheijden, 2012). While emotional eating corresponds to the tendency to overeat as an inappropriate response to negative emotions and distress (Elfhag & Morey, 2008; Heatherton, Herman, & Polivy, 1991; Van Strien et al., 2012), external eating refers to eating in response to external foodrelated cues, such as seeing or smelling food (Elfhag & Morey, 2008; Van Strien et al., 2012). Another dimension related to overeating is binge eating, which is characterized by the occurrence of episodes of consumption of a large amount of food in a brief period of time and a sense of lack of control during those episodes (American Psychiatric Association, 2013; Wolfe et al., 2009). Somewhat opposing these three dimensions, dietary restraint implies conscious attempts to reduce food intake in order to control body weight (Elfhag & Morey, 2008; Van Strien et al., 2012). Westenhoefer (1991) distinguished two types of restriction: while the rigid control of eating behaviour is characterized by dichotomous attitudes regarding which foods to exclude, and is related to higher disinhibition and higher food consumption after preload, flexible control corresponds to a less strict type of restriction, being therefore associated to lower disinhibition (Viana, 2002; Westenhoefer et al., 1994). Self-efficacy has shown to be a good predictor of eating behaviour (Conn, 1997; Strecher et al., 1986). Self-efficacy refers to the beliefs in the ability to organize and implement the action plans needed to achieve a certain result and the feeling of control over the behaviours and environment (Bandura, 1997), being specific for each task or domain, as for example eating self-efficacy (AbuSabha & Achterberg, 1997; Bandura, 1997; Hofstetter, Sallis, & Hovell, 1990). The perception of one’s own eating efficacy may be related to particular eating behaviour dimensions: it has been opposed to disinhibition and bulimic-related eating behaviours (Verstuyf et al., 2012), and a binge eating episode implies a sense of lack of control over eating (American Psychiatric Association, 2013; Wolfe et al., 2009), which might be related to low eating self-efficacy. Given some discrepancies in previous research and the lack of work studying eating behaviour dimensions among students from nutrition vs. other courses, our main aim was to compare several eating behaviour dimensions between undergraduate nutrition students and students from other courses. In the female subsample we simultaneously studied the effect of the course’s year of attendance on the results. Methods Sample The study was conducted on two convenience samples of Portuguese higher education students: a sample of students attending the undergraduate course of Nutrition and Food Sciences at the Faculty of Nutrition and Food Sciences of the University of Porto (“Nutrition students”), and a sample of undergraduate students from other areas in Portuguese public and private institutions (“Other courses”). The inclusion criteria for both samples were being a student between 18 and 27 years of age, and free from dependency conditions that could constrain free and informed decisionmaking regarding their participation were included. The exclusion of students over 27 years aimed to reduce socio-demographic heterogeneity. Due to the small sample size of students attending the third and fourth years, these were combined, after verifying the absence of significant differences in all eating behaviour
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dimensions between students from the two years. Moreover, in the sample of students from other courses, potential participants with complete or incomplete academic training in the areas of Nutrition and Dietetics were not included and only students attending undergraduate or integrated master degrees were considered. The students from both samples were approached within the institutions where they attended their courses, mainly during classes and after previous contact with the responsible teacher. For the Nutrition students sample 215 students were approached, from which 3 (1.4%) refused to participate. The sample of students from other courses came from a larger sample which included students attending the fifth years of their courses; as refusals were not registered by year, the participation rate is reported for this broader sample, being of 91.9% (362 from 394 approaches). A total of 344 (95.0%) of these students were attending the first to fourth year of their course, being therefore included in the sample. Due to incompleteness of the questionnaires, data from 58 participants in the Nutrition students’ sample (27.4%) and from 81 students attending other courses (23.5%) were not analysed. Hence, we analysed data from 154 nutrition students and from 263 students from other courses (Basic education: n = 55; History: n = 48; Psychology: n = 45; Dental Medicine: n = 40; Electrotechnical Engineering: n = 27; History of Art: n = 20; Political Science: n = 18; Geography: n = 8; Architecture: n = 2). The overrepresentation of females in both subsamples is in line with the greater proportion of females in the Portuguese higher education (Direção-Geral de Estatísticas da Educação e Ciência, 2013). Nevertheless, as sex differences in eating behaviour are reported by several authors (Elfhag & Morey, 2008; Konttinen et al., 2009; Poínhos, Oliveira, & Correia, 2013; Poínhos, Rowcliffe, et al., 2013; Van Strien, Herman, & Verheijden, 2009; Van Strien et al., 2012; Viana & Sinde, 2003), all the analysis was performed separately for the subsamples of females and males. Procedure This study was conducted according to the guidelines laid down in the Declaration of Helsinki and all procedures involving human participants were approved by the ethics committee of Centro Hospitalar de São João, E.P.E. (Porto, Portugal). Data were collected between February and July 2012. All procedures were standardized prior to data collection. Students were invited to participate, and a written document with the study’s conditions of participation, aims and overall description was provided. After clarifying doubts, written informed consent was obtained from all students willing to participate. Participants then answered a sociodemographic and anthropometric questionnaire, where they selfreported their sex, age, education, height, and current weight (without shoes and clothing; BMI [kg/m2] was afterwards calculated as weight divided by squared height). Finally, eating behaviour questionnaires were answered. All questionnaires were selfadministered in a written format, in the presence of an investigator. Measures The Dutch Eating Behavior Questionnaire (DEBQ; Van Strien et al., 1986) was used to measure emotional and external eating. DEBQ’s restraint scale was not used, as we considered separately the flexible and rigid control of eating behaviour. Both the emotional eating (13 items) and the external eating (10 items) DEBQ scales showed good internal consistency in the Portuguese version of DEBQ (Cronbach’s alpha of 0.94 and 0.81, respectively; Viana & Sinde, 2003). The flexible and rigid controls of eating behaviour were measured using the subscales proposed by Westenhoefer, Stunkard, and Pudel (1999), recently adapted and validated for Portuguese adults (Poínhos, Rowcliffe, et al., 2013). The Portuguese version of these
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R. Poínhos et al./Appetite 84 (2014) 28–33
subscales comprise 11 and 14 items respectively, and showed acceptable internal consistency in samples of the general population and higher education students (Cronbach’s alpha between 0.75 and 0.82). To assess binge eating severity we used the Portuguese version of the Binge Eating Scale (BES; Freitas et al., 2001; original version: Gormally et al., 1982), composed of 16 items. When our study began the BES was not yet adapted for the European Portuguese, and so slight linguistic adjustments were made from the Brazilian Portuguese version. Both Portuguese versions have similar formulation of items and have shown good internal consistency (Freitas et al., 2006; Tapadinhas & Ribeiro, 2012; Cronbach’s alpha of 0.87 and 0.89, respectively). Eating self-efficacy was measured using the General Eating SelfEfficacy Scale (GESES; Poínhos, Canelas, et al., 2013). This recently developed 5-item scale showed to be a valid and reliable instrument to measure general features of eating self-efficacy (Cronbach’s alpha values above 0.85). Statistical analysis Descriptive statistics included frequencies (n; %), means and standard deviations (SD), and medians and percentiles (P25; P75). Normality was assessed using the skewness and kurtosis. Due to the positive skewness of data, BMI and BES values were logtransformed prior to analysis, although for ease of interpretation, they are presented after exponential conversion to the original scale. In the female subsamples, each eating behaviour dimension was compared between the two samples (Nutrition students vs. Other courses) and the year of course attended (1st vs. 2nd vs. 3rd and 4th). Given the smaller sample sizes, comparisons among males were made only between courses. In both sexes, univariate analysis of variance was used, including BMI as covariate. Prior to the main analysis, univariate analysis of variance and independent samples t-tests were used, respectively, to compare BMI among female and male groups. Whenever applicable, Bonferroni’s correction was used to adjust p-values for the number of pairs compared, in order to avoid the inflation of type I errors. Partial eta squared (ηp2) was used to quantify the effect sizes, the effect being classified as small (ηp2 < 0.035), medium (0.035 ≤ ηp2 < 0.100) or large (ηp2 ≥ 0.100; Cohen, 1988). All analyses were performed using IBM SPSS Statistics for Windows, version 21.0 (IBM Corp., 2012). Values of P below 0.05 were considered statistically significant. Results BMI description and comparison among groups Table 1 describes BMI in both samples by year (only for females) and sex, as well as the respective sub-sample sizes. The univariate ANOVA revealed a main effect of course (F1;302 = 7.507; P = 0.007),
Table 1 BMI by course, year and sex.
Nutrition sciences Other courses
1st year 2nd year 3rd/4th years 1st year 2nd year 3rd/4th years
Females
Males
n
Median (P25; P75)
n
Median (P25; P75)
36 49 50 54 78 41
19.7 (19.1; 21.8) 20.7 (19.4; 23.1) 20.6 (19.4; 22.6) 21.2 (19.9; 24.5) 21.1 (19.7; 22.7) 20.7 (19.6; 23.2)
19
23.5 (22.4; 25.2)
90
22.6 (20.7; 24.1)
with female nutrition students presenting lower BMI values than female students from other courses. No main effect of year was observed (F 2;301 < 1; P = 0.988) among females, but a significant interaction among the two factors was found (F2;302 = 3.353; P = 0.036), corresponding to lower BMI in female nutrition students attending the first year and in females from other courses attending the third and fourth years. For males, no differences were found for BMI between the two samples (t107 = 1.308; P = 0.194).
Comparison of eating behaviour dimensions among groups The results comparing each eating behaviour dimension among females are presented in Table 2. Female nutrition students present higher eating restraint (both flexible and rigid control) and higher binge eating; the effect on binge eating was small, while the effects on restraint were medium, the one regarding rigid control being the largest. No main effect of year was found for any dimension, as well as no significant interaction. Male nutrition students showed higher flexible and rigid control of eating behaviour when compared with students from other courses. Both effects were medium, but the effect on rigid control was larger. Table 3 presents the results comparing each eating behaviour dimension among males.
Discussion The main aim of this study was to compare eating behaviour dimensions of undergraduate nutrition students from those attending other courses. Our main results were the higher level of dietary restraint (both flexible and rigid control of eating behaviour) found in nutrition students from both sexes when compared to students from other courses. We also found that female nutrition students presented higher binge eating levels than those attending other courses. Regarding dietary restraint, in a sample of students from both sexes, Korinth et al. (2009) found similar results, with nutrition students presenting higher levels of both types of restraint than their colleagues from other courses. Moreover, Kinzl et al. (2006) report high levels of dietary restraint in more than 40% of a female dieticians’ sample. It is worth noticing that, for both sexes, the effects sizes found in our study were larger for rigid control than for flexible control. This result is particularly relevant given the conceptual distinction between these two restriction types, as rigid control is characterized by dichotomous attitudes regarding food and associated with higher disinhibition (Viana, 2002; Westenhoefer et al., 1994), which may lead to worse weight-related outcomes among nutrition students despite their higher knowledge on nutrition, food and dieting. The previous remarks regarding dietary restraint may indeed help in the interpretation of some secondary findings regarding BMI. The higher restraint levels in female nutrition students and the larger effect size for rigid control may partially explain that, within female nutrition students those attending the first year had lower BMI values, whereas among females from other courses the ones in the earlier years had higher BMI values. This may reflect worst weightrelated outcomes among nutrition students throughout their course (which needs to be addressed in future longitudinal studies), due not only to the effect of the two types of dietary restraint, but also to the higher levels of binge eating. The higher binge eating levels found among female nutrition students is in line with the results of Reinstein et al. (1992), which revealed that students coursing dietetics and food science scored higher in behaviours related to binge eating than students from other majors. In our study this effect was not significant among males,
0.016 0.006 0.005 0.006 0.015 0.002 0.092 0.412 0.463 0.417 0.101 0.754 0.002 0.009 0.004 0.002 0.010 0.018
Emotional eating External eating Flexible control Rigid control Binge eating Eating self-efficacy
Nutrition students (n = 19) Mean (SD)
Other courses (n = 90) Mean (SD)
Pa
ηp2a
1.76 (0.67) 2.56 (0.56) 5.53 (2.09) 5.89 (2.31) 4.84 (1.11) 14.42 (3.19)
1.56 (0.65) 2.77 (0.63) 4.10 (2.53) 3.88 (2.91) 3.29 (1.21) 13.76 (3.76)
0.267 0.203 0.043 0.012 0.157 0.390
0.012 0.015 0.038 0.058 0.019 0.007
Univariate ANOVA, with BMI as covariate. a Comparison between Nutrition students and Other courses.
0.001 0.002 0.036 0.059 0.016 0.002 0.535 0.493 0.001 <0.001 0.026 0.490 2.17 (0.94) 2.71 (0.56) 5.61 (2.29) 5.54 (3.07) 4.13 (1.52) 13.00 (3.81) 1.98 (0.78) 2.78 (0.62) 5.54 (2.95) 4.77 (3.04) 3.88 (1.14) 12.51 (3.50) 2.16 (0.81) 2.76 (0.71) 4.96 (2.95) 5.07 (3.23) 4.23 (1.55) 11.76 (4.25) 2-factor univariate ANOVA, with BMI as covariate. a Main effect of course (Nutrition students vs. Other courses). b Main effect of year (1st vs. 2nd vs. 3rd/4th). c Interaction between course and year.
2.10 (0.78) 2.80 (0.54) 6.38 (2.55) 6.14 (2.39) 3.57 (1.20) 13.76 (3.07) 2.30 (0.73) 2.92 (0.56) 6.20 (2.44) 6.47 (2.64) 5.74 (0.87) 12.45 (2.95) 1.94 (0.82) 2.68 (0.51) 6.14 (2.70) 5.92 (3.17) 5.26 (1.00) 12.78 (3.06) Emotional eating External eating Flexible control Rigid control Binge eating Eating self-efficacy
P
31
Table 3 Comparison of each eating behaviour dimension among male samples.
0.687 0.263 0.521 0.692 0.227 0.065
ηp2 P P
Course × yearc Other courses
3rd/4th years (n = 50) Mean (SD) 2nd year (n = 49) Mean (SD) 1st year (n = 36) Mean (SD)
Nutrition students
Table 2 Comparison of each eating behaviour dimension among female groups.
1st year (n = 54) Mean (SD)
2nd year (n = 78) Mean (SD)
3rd/4th years (n = 41) Mean (SD)
Coursea
ηp2
Yearb
ηp2
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which may be due to the small number of male nutrition students. Despite this limitation, which will be discussed ahead, this result seems relevant, as the effect size among males is similar to the one found for female students. Regarding other dimensions, no significant differences were found between nutrition and non-nutrition students. If, on one hand, the lack of studies evaluating eating behaviour dimensions among nutrition students makes these results difficult to discuss, it also highlights their relevance. Indeed, to our knowledge no other work had previously assessed all eating behaviour dimensions considered in the current study among nutrition students. No main effect of year or significant interaction between year and course were found for any eating behaviour dimension. A transversal study by Costa et al. (2007) found that Portuguese female students coursing different years of the Nutrition major didn’t differ regarding dietary restraint, disinhibition and hunger (as assessed by the Three Factor Eating Questionnaire; TFEQ). Nevertheless, in a related longitudinal study which compared Portuguese female students when coursing the 1st and 3rd years of their Nutrition course, a significant decrease in TFEQ’s disinhibition dimension was reported, but no differences regarding the other two dimensions (restraint and hunger; Costa et al., 2007). These results highlight the importance of differentiating between conclusions drawn from transversal or longitudinal studies. Therefore, in future research we intend to repeat the analysis used in the current study but within a longitudinal design. This approach may identify some effects of the year of course not revealed by the current study. A relevant research topic will be the interaction between year and course regarding the two types of dietary restraint, as the differences in disinhibition but not in restraint reported by Costa et al. (2007) and the larger effect sizes found in our study for rigid control may indicate differences among nutrition students throughout the course specifically in rigid control. As previously referred, some authors suggest that the selection of a nutrition course is influenced by one’s own personal experiences regarding food and weight control (Drake, 1989; Hughes & Desbrow, 2005; Magalhães & Motta, 2012; McArthur, 1995) or by a prior tendency to disordered eating behaviours (Stipp & de Oliveira, 2003). On the other hand, this possibility is against the opinion of those suggesting that the contact with food-related issues and the belief on the importance of a good appearance for future professional success may be favourable to a higher incidence of eating disorders (Fiates & Salles, 2001; Penz et al., 2008). Considering this effect there would be a tendency towards a more inadequate eating behaviour throughout the attendance of the nutrition course. Longitudinal studies will also be relevant to further clarify these divergent opinions. Despite some limitations of our study, namely the use of convenience samples, the distinct course areas’ sample sizes, and the reduced number of male nutrition students’ participants, its importance is highlighted given the lack of knowledge and controversies in this field. It is worth noticing that the small number of male
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nutrition students is in line with their proportion in this course. Future research could deal with this limitation by including nutrition students from more than one institution and comparing them with undergraduate students from other courses according to their sex, age, and institution. The use of reported anthropometric data also is a limitation of the current study. However, we believe this limitation had little influence on our results, as Poínhos et al. (2011) studied a representative sample of the Portuguese adult population and report very strong associations (r > 0.97) and small discrepancies (mean = 1.14%; SD = 2.83% for 18–29 years age group) between BMI calculated from reported and measured weight and height. In conclusion, nutrition students presented higher restraint and binge eating. These results may have clinical implications, as the nutritionists’ performance may be biased by their own eating behaviour characteristics. It is worth noticing that only recently binge eating disorder was formally classified as an eating behaviour disorder by the American Psychiatric Association (2013); therefore, these results should also have educational implications, as the relevance of binge eating should be focused accordingly throughout the nutrition courses’ curricula. Moreover, the data obtained from this study provide several clues to further studies to be developed regarding the still rarely approached issue of eating behaviour among nutrition students.
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Appetite j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / a p p e t
Research report
Eating behaviour among undergraduate students. Comparing nutrition students with other courses ☆ Rui Poínhos a,*, Diogo Alves, Elisée Vieira, Sílvia Pinhão a,b, Bruno M.P.M. Oliveira a,c, Flora Correia a,b,d a
Faculdade de Ciências da Nutrição e Alimentação, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal Centro Hospitalar de São João, E.P.E., Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal c Laboratório de Inteligência Artificial e Apoio à Decisão, Instituto de Engenharia de Sistemas e Computadores, Tecnologia e Ciência, Rua Dr. Roberto Frias, 378, 4200-465 Porto, Portugal d Unidade de Investigação e Desenvolvimento de Nefrologia, Faculdade de Medicina, Universidade do Porto, Alameda Prof. Hernâni Monteiro, 4200-319 Porto, Portugal b
A R T I C L E
I N F O
Article history: Received 6 August 2014 Received in revised form 9 September 2014 Accepted 13 September 2014 Available online 21 September 2014 Keywords: Eating behaviour Nutrition students Higher education students Body mass index
A B S T R A C T
Our main aim was to compare eating behaviour between Portuguese undergraduate nutrition students and students attending other courses. Several eating behaviour dimensions were compared between 154 nutrition students and 263 students from other areas. Emotional and external eating were assessed by the Dutch Eating Behavior Questionnaire, dietary restraint was measured using the flexible and rigid control of eating behaviour subscales, binge eating was measured using the Binge Eating Scale, and eating selfefficacy using the General Eating Self-Efficacy Scale. Higher levels of flexible and rigid control were found in nutrition students from both sexes when compared to students from other courses. Female nutrition students also presented higher binge eating levels than their colleagues from other courses. To our knowledge no other work has previously assessed all eating behaviour dimensions considered in the current study among nutrition students. Besides the results by themselves, the data obtained from this study provide several clues to further studies to be developed regarding the still rarely approached issue of eating behaviour among nutrition students. © 2014 Elsevier Ltd. All rights reserved.
Introduction Several studies suggest that eating disorders or the risk for disordered eating behaviour are more prevalent in dietetic or nutrition students when compared with students from other courses (Drake, 1989; Fiates & Salles, 2001; Gonidakis et al., 2009; Kolka & Abayomi, 2012; Laus, Moreira, & Costa, 2009; Reinstein et al., 1992; Worobey & Schoenfeld, 1999). In some studies, although the differences were not significant, the results suggest a higher prevalence of risk of eating disorders among nutrition students (Dos Santos, Meneguci, & De Mendonça, 2008; Fredenberg, Berglund, & Dieken, 1996; Stipp & de Oliveira, 2003). Nevertheless, results from other studies suggest
☆ Acknowledgements: This work is part-funded by the ERDF – European Regional Development Fund through the COMPETE Programme (operational programme for competitiveness) and by National Funds through the FCT – Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) within projects PTDC/MAT/121107/2010 and FCOMP – 01-0124-FEDER-037281. The funders had no role in the design, analysis or writing of this article. * Corresponding author. E-mail address: [email protected] (R. Poínhos).
http://dx.doi.org/10.1016/j.appet.2014.09.011 0195-6663/© 2014 Elsevier Ltd. All rights reserved.
that nutrition and dietetic students are not different regarding disordered eating behaviour from other courses (Johnston & Christopher, 1991; Kiziltan & Karabudak, 2008; Mealha et al., 2013; Swezda & Thorne, 2002) or groups (Torresani, 2003) or even that nutrition students have lower risk of disordered eating behaviour when compared to pre-med students (Mehr et al., 2005). Even considering data indicating that students of nutrition and dietetics present a higher prevalence of eating disorder behaviour, the causal relationship still remains unknown (Korinth, Schiess, & Westenhoefer, 2009; Morgan, Vecchiatti, & Negrão, 2002). While some authors suggest that the selection of a nutrition or dietetics course is influenced by own personal experiences regarding food and weight control (Drake, 1989; Hughes & Desbrow, 2005; Magalhães & Motta, 2012; McArthur, 1995) or by a prior tendency to those behaviours (Stipp & de Oliveira, 2003), others suggest that the contact with food issues and the belief that a good appearance will be important for future professional success may be favourable to a higher incidence of eating disorders in nutrition students (Fiates & Salles, 2001; Penz, Dal Bosco, & Vieira, 2008). Despite the recognition of its importance (Drummond & Hare, 2012; Houston, Bassler, & Anderson, 2008; Korinth et al., 2009),studies focusing on eating behaviour among nutrition and
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dietetics students and professionals mostly study the prevalence or risk of eating disorders, and few evaluate eating behaviour dimensions. For instance, both emotional and external eating are eating behaviour dimensions associated with overeating, weight gain and higher body mass index (BMI; Elfhag & Linné, 2005; Koenders & Van Strien, 2011; Van Strien, Herman, & Verheijden, 2012). While emotional eating corresponds to the tendency to overeat as an inappropriate response to negative emotions and distress (Elfhag & Morey, 2008; Heatherton, Herman, & Polivy, 1991; Van Strien et al., 2012), external eating refers to eating in response to external foodrelated cues, such as seeing or smelling food (Elfhag & Morey, 2008; Van Strien et al., 2012). Another dimension related to overeating is binge eating, which is characterized by the occurrence of episodes of consumption of a large amount of food in a brief period of time and a sense of lack of control during those episodes (American Psychiatric Association, 2013; Wolfe et al., 2009). Somewhat opposing these three dimensions, dietary restraint implies conscious attempts to reduce food intake in order to control body weight (Elfhag & Morey, 2008; Van Strien et al., 2012). Westenhoefer (1991) distinguished two types of restriction: while the rigid control of eating behaviour is characterized by dichotomous attitudes regarding which foods to exclude, and is related to higher disinhibition and higher food consumption after preload, flexible control corresponds to a less strict type of restriction, being therefore associated to lower disinhibition (Viana, 2002; Westenhoefer et al., 1994). Self-efficacy has shown to be a good predictor of eating behaviour (Conn, 1997; Strecher et al., 1986). Self-efficacy refers to the beliefs in the ability to organize and implement the action plans needed to achieve a certain result and the feeling of control over the behaviours and environment (Bandura, 1997), being specific for each task or domain, as for example eating self-efficacy (AbuSabha & Achterberg, 1997; Bandura, 1997; Hofstetter, Sallis, & Hovell, 1990). The perception of one’s own eating efficacy may be related to particular eating behaviour dimensions: it has been opposed to disinhibition and bulimic-related eating behaviours (Verstuyf et al., 2012), and a binge eating episode implies a sense of lack of control over eating (American Psychiatric Association, 2013; Wolfe et al., 2009), which might be related to low eating self-efficacy. Given some discrepancies in previous research and the lack of work studying eating behaviour dimensions among students from nutrition vs. other courses, our main aim was to compare several eating behaviour dimensions between undergraduate nutrition students and students from other courses. In the female subsample we simultaneously studied the effect of the course’s year of attendance on the results. Methods Sample The study was conducted on two convenience samples of Portuguese higher education students: a sample of students attending the undergraduate course of Nutrition and Food Sciences at the Faculty of Nutrition and Food Sciences of the University of Porto (“Nutrition students”), and a sample of undergraduate students from other areas in Portuguese public and private institutions (“Other courses”). The inclusion criteria for both samples were being a student between 18 and 27 years of age, and free from dependency conditions that could constrain free and informed decisionmaking regarding their participation were included. The exclusion of students over 27 years aimed to reduce socio-demographic heterogeneity. Due to the small sample size of students attending the third and fourth years, these were combined, after verifying the absence of significant differences in all eating behaviour
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dimensions between students from the two years. Moreover, in the sample of students from other courses, potential participants with complete or incomplete academic training in the areas of Nutrition and Dietetics were not included and only students attending undergraduate or integrated master degrees were considered. The students from both samples were approached within the institutions where they attended their courses, mainly during classes and after previous contact with the responsible teacher. For the Nutrition students sample 215 students were approached, from which 3 (1.4%) refused to participate. The sample of students from other courses came from a larger sample which included students attending the fifth years of their courses; as refusals were not registered by year, the participation rate is reported for this broader sample, being of 91.9% (362 from 394 approaches). A total of 344 (95.0%) of these students were attending the first to fourth year of their course, being therefore included in the sample. Due to incompleteness of the questionnaires, data from 58 participants in the Nutrition students’ sample (27.4%) and from 81 students attending other courses (23.5%) were not analysed. Hence, we analysed data from 154 nutrition students and from 263 students from other courses (Basic education: n = 55; History: n = 48; Psychology: n = 45; Dental Medicine: n = 40; Electrotechnical Engineering: n = 27; History of Art: n = 20; Political Science: n = 18; Geography: n = 8; Architecture: n = 2). The overrepresentation of females in both subsamples is in line with the greater proportion of females in the Portuguese higher education (Direção-Geral de Estatísticas da Educação e Ciência, 2013). Nevertheless, as sex differences in eating behaviour are reported by several authors (Elfhag & Morey, 2008; Konttinen et al., 2009; Poínhos, Oliveira, & Correia, 2013; Poínhos, Rowcliffe, et al., 2013; Van Strien, Herman, & Verheijden, 2009; Van Strien et al., 2012; Viana & Sinde, 2003), all the analysis was performed separately for the subsamples of females and males. Procedure This study was conducted according to the guidelines laid down in the Declaration of Helsinki and all procedures involving human participants were approved by the ethics committee of Centro Hospitalar de São João, E.P.E. (Porto, Portugal). Data were collected between February and July 2012. All procedures were standardized prior to data collection. Students were invited to participate, and a written document with the study’s conditions of participation, aims and overall description was provided. After clarifying doubts, written informed consent was obtained from all students willing to participate. Participants then answered a sociodemographic and anthropometric questionnaire, where they selfreported their sex, age, education, height, and current weight (without shoes and clothing; BMI [kg/m2] was afterwards calculated as weight divided by squared height). Finally, eating behaviour questionnaires were answered. All questionnaires were selfadministered in a written format, in the presence of an investigator. Measures The Dutch Eating Behavior Questionnaire (DEBQ; Van Strien et al., 1986) was used to measure emotional and external eating. DEBQ’s restraint scale was not used, as we considered separately the flexible and rigid control of eating behaviour. Both the emotional eating (13 items) and the external eating (10 items) DEBQ scales showed good internal consistency in the Portuguese version of DEBQ (Cronbach’s alpha of 0.94 and 0.81, respectively; Viana & Sinde, 2003). The flexible and rigid controls of eating behaviour were measured using the subscales proposed by Westenhoefer, Stunkard, and Pudel (1999), recently adapted and validated for Portuguese adults (Poínhos, Rowcliffe, et al., 2013). The Portuguese version of these
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subscales comprise 11 and 14 items respectively, and showed acceptable internal consistency in samples of the general population and higher education students (Cronbach’s alpha between 0.75 and 0.82). To assess binge eating severity we used the Portuguese version of the Binge Eating Scale (BES; Freitas et al., 2001; original version: Gormally et al., 1982), composed of 16 items. When our study began the BES was not yet adapted for the European Portuguese, and so slight linguistic adjustments were made from the Brazilian Portuguese version. Both Portuguese versions have similar formulation of items and have shown good internal consistency (Freitas et al., 2006; Tapadinhas & Ribeiro, 2012; Cronbach’s alpha of 0.87 and 0.89, respectively). Eating self-efficacy was measured using the General Eating SelfEfficacy Scale (GESES; Poínhos, Canelas, et al., 2013). This recently developed 5-item scale showed to be a valid and reliable instrument to measure general features of eating self-efficacy (Cronbach’s alpha values above 0.85). Statistical analysis Descriptive statistics included frequencies (n; %), means and standard deviations (SD), and medians and percentiles (P25; P75). Normality was assessed using the skewness and kurtosis. Due to the positive skewness of data, BMI and BES values were logtransformed prior to analysis, although for ease of interpretation, they are presented after exponential conversion to the original scale. In the female subsamples, each eating behaviour dimension was compared between the two samples (Nutrition students vs. Other courses) and the year of course attended (1st vs. 2nd vs. 3rd and 4th). Given the smaller sample sizes, comparisons among males were made only between courses. In both sexes, univariate analysis of variance was used, including BMI as covariate. Prior to the main analysis, univariate analysis of variance and independent samples t-tests were used, respectively, to compare BMI among female and male groups. Whenever applicable, Bonferroni’s correction was used to adjust p-values for the number of pairs compared, in order to avoid the inflation of type I errors. Partial eta squared (ηp2) was used to quantify the effect sizes, the effect being classified as small (ηp2 < 0.035), medium (0.035 ≤ ηp2 < 0.100) or large (ηp2 ≥ 0.100; Cohen, 1988). All analyses were performed using IBM SPSS Statistics for Windows, version 21.0 (IBM Corp., 2012). Values of P below 0.05 were considered statistically significant. Results BMI description and comparison among groups Table 1 describes BMI in both samples by year (only for females) and sex, as well as the respective sub-sample sizes. The univariate ANOVA revealed a main effect of course (F1;302 = 7.507; P = 0.007),
Table 1 BMI by course, year and sex.
Nutrition sciences Other courses
1st year 2nd year 3rd/4th years 1st year 2nd year 3rd/4th years
Females
Males
n
Median (P25; P75)
n
Median (P25; P75)
36 49 50 54 78 41
19.7 (19.1; 21.8) 20.7 (19.4; 23.1) 20.6 (19.4; 22.6) 21.2 (19.9; 24.5) 21.1 (19.7; 22.7) 20.7 (19.6; 23.2)
19
23.5 (22.4; 25.2)
90
22.6 (20.7; 24.1)
with female nutrition students presenting lower BMI values than female students from other courses. No main effect of year was observed (F 2;301 < 1; P = 0.988) among females, but a significant interaction among the two factors was found (F2;302 = 3.353; P = 0.036), corresponding to lower BMI in female nutrition students attending the first year and in females from other courses attending the third and fourth years. For males, no differences were found for BMI between the two samples (t107 = 1.308; P = 0.194).
Comparison of eating behaviour dimensions among groups The results comparing each eating behaviour dimension among females are presented in Table 2. Female nutrition students present higher eating restraint (both flexible and rigid control) and higher binge eating; the effect on binge eating was small, while the effects on restraint were medium, the one regarding rigid control being the largest. No main effect of year was found for any dimension, as well as no significant interaction. Male nutrition students showed higher flexible and rigid control of eating behaviour when compared with students from other courses. Both effects were medium, but the effect on rigid control was larger. Table 3 presents the results comparing each eating behaviour dimension among males.
Discussion The main aim of this study was to compare eating behaviour dimensions of undergraduate nutrition students from those attending other courses. Our main results were the higher level of dietary restraint (both flexible and rigid control of eating behaviour) found in nutrition students from both sexes when compared to students from other courses. We also found that female nutrition students presented higher binge eating levels than those attending other courses. Regarding dietary restraint, in a sample of students from both sexes, Korinth et al. (2009) found similar results, with nutrition students presenting higher levels of both types of restraint than their colleagues from other courses. Moreover, Kinzl et al. (2006) report high levels of dietary restraint in more than 40% of a female dieticians’ sample. It is worth noticing that, for both sexes, the effects sizes found in our study were larger for rigid control than for flexible control. This result is particularly relevant given the conceptual distinction between these two restriction types, as rigid control is characterized by dichotomous attitudes regarding food and associated with higher disinhibition (Viana, 2002; Westenhoefer et al., 1994), which may lead to worse weight-related outcomes among nutrition students despite their higher knowledge on nutrition, food and dieting. The previous remarks regarding dietary restraint may indeed help in the interpretation of some secondary findings regarding BMI. The higher restraint levels in female nutrition students and the larger effect size for rigid control may partially explain that, within female nutrition students those attending the first year had lower BMI values, whereas among females from other courses the ones in the earlier years had higher BMI values. This may reflect worst weightrelated outcomes among nutrition students throughout their course (which needs to be addressed in future longitudinal studies), due not only to the effect of the two types of dietary restraint, but also to the higher levels of binge eating. The higher binge eating levels found among female nutrition students is in line with the results of Reinstein et al. (1992), which revealed that students coursing dietetics and food science scored higher in behaviours related to binge eating than students from other majors. In our study this effect was not significant among males,
0.016 0.006 0.005 0.006 0.015 0.002 0.092 0.412 0.463 0.417 0.101 0.754 0.002 0.009 0.004 0.002 0.010 0.018
Emotional eating External eating Flexible control Rigid control Binge eating Eating self-efficacy
Nutrition students (n = 19) Mean (SD)
Other courses (n = 90) Mean (SD)
Pa
ηp2a
1.76 (0.67) 2.56 (0.56) 5.53 (2.09) 5.89 (2.31) 4.84 (1.11) 14.42 (3.19)
1.56 (0.65) 2.77 (0.63) 4.10 (2.53) 3.88 (2.91) 3.29 (1.21) 13.76 (3.76)
0.267 0.203 0.043 0.012 0.157 0.390
0.012 0.015 0.038 0.058 0.019 0.007
Univariate ANOVA, with BMI as covariate. a Comparison between Nutrition students and Other courses.
0.001 0.002 0.036 0.059 0.016 0.002 0.535 0.493 0.001 <0.001 0.026 0.490 2.17 (0.94) 2.71 (0.56) 5.61 (2.29) 5.54 (3.07) 4.13 (1.52) 13.00 (3.81) 1.98 (0.78) 2.78 (0.62) 5.54 (2.95) 4.77 (3.04) 3.88 (1.14) 12.51 (3.50) 2.16 (0.81) 2.76 (0.71) 4.96 (2.95) 5.07 (3.23) 4.23 (1.55) 11.76 (4.25) 2-factor univariate ANOVA, with BMI as covariate. a Main effect of course (Nutrition students vs. Other courses). b Main effect of year (1st vs. 2nd vs. 3rd/4th). c Interaction between course and year.
2.10 (0.78) 2.80 (0.54) 6.38 (2.55) 6.14 (2.39) 3.57 (1.20) 13.76 (3.07) 2.30 (0.73) 2.92 (0.56) 6.20 (2.44) 6.47 (2.64) 5.74 (0.87) 12.45 (2.95) 1.94 (0.82) 2.68 (0.51) 6.14 (2.70) 5.92 (3.17) 5.26 (1.00) 12.78 (3.06) Emotional eating External eating Flexible control Rigid control Binge eating Eating self-efficacy
P
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Table 3 Comparison of each eating behaviour dimension among male samples.
0.687 0.263 0.521 0.692 0.227 0.065
ηp2 P P
Course × yearc Other courses
3rd/4th years (n = 50) Mean (SD) 2nd year (n = 49) Mean (SD) 1st year (n = 36) Mean (SD)
Nutrition students
Table 2 Comparison of each eating behaviour dimension among female groups.
1st year (n = 54) Mean (SD)
2nd year (n = 78) Mean (SD)
3rd/4th years (n = 41) Mean (SD)
Coursea
ηp2
Yearb
ηp2
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which may be due to the small number of male nutrition students. Despite this limitation, which will be discussed ahead, this result seems relevant, as the effect size among males is similar to the one found for female students. Regarding other dimensions, no significant differences were found between nutrition and non-nutrition students. If, on one hand, the lack of studies evaluating eating behaviour dimensions among nutrition students makes these results difficult to discuss, it also highlights their relevance. Indeed, to our knowledge no other work had previously assessed all eating behaviour dimensions considered in the current study among nutrition students. No main effect of year or significant interaction between year and course were found for any eating behaviour dimension. A transversal study by Costa et al. (2007) found that Portuguese female students coursing different years of the Nutrition major didn’t differ regarding dietary restraint, disinhibition and hunger (as assessed by the Three Factor Eating Questionnaire; TFEQ). Nevertheless, in a related longitudinal study which compared Portuguese female students when coursing the 1st and 3rd years of their Nutrition course, a significant decrease in TFEQ’s disinhibition dimension was reported, but no differences regarding the other two dimensions (restraint and hunger; Costa et al., 2007). These results highlight the importance of differentiating between conclusions drawn from transversal or longitudinal studies. Therefore, in future research we intend to repeat the analysis used in the current study but within a longitudinal design. This approach may identify some effects of the year of course not revealed by the current study. A relevant research topic will be the interaction between year and course regarding the two types of dietary restraint, as the differences in disinhibition but not in restraint reported by Costa et al. (2007) and the larger effect sizes found in our study for rigid control may indicate differences among nutrition students throughout the course specifically in rigid control. As previously referred, some authors suggest that the selection of a nutrition course is influenced by one’s own personal experiences regarding food and weight control (Drake, 1989; Hughes & Desbrow, 2005; Magalhães & Motta, 2012; McArthur, 1995) or by a prior tendency to disordered eating behaviours (Stipp & de Oliveira, 2003). On the other hand, this possibility is against the opinion of those suggesting that the contact with food-related issues and the belief on the importance of a good appearance for future professional success may be favourable to a higher incidence of eating disorders (Fiates & Salles, 2001; Penz et al., 2008). Considering this effect there would be a tendency towards a more inadequate eating behaviour throughout the attendance of the nutrition course. Longitudinal studies will also be relevant to further clarify these divergent opinions. Despite some limitations of our study, namely the use of convenience samples, the distinct course areas’ sample sizes, and the reduced number of male nutrition students’ participants, its importance is highlighted given the lack of knowledge and controversies in this field. It is worth noticing that the small number of male
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nutrition students is in line with their proportion in this course. Future research could deal with this limitation by including nutrition students from more than one institution and comparing them with undergraduate students from other courses according to their sex, age, and institution. The use of reported anthropometric data also is a limitation of the current study. However, we believe this limitation had little influence on our results, as Poínhos et al. (2011) studied a representative sample of the Portuguese adult population and report very strong associations (r > 0.97) and small discrepancies (mean = 1.14%; SD = 2.83% for 18–29 years age group) between BMI calculated from reported and measured weight and height. In conclusion, nutrition students presented higher restraint and binge eating. These results may have clinical implications, as the nutritionists’ performance may be biased by their own eating behaviour characteristics. It is worth noticing that only recently binge eating disorder was formally classified as an eating behaviour disorder by the American Psychiatric Association (2013); therefore, these results should also have educational implications, as the relevance of binge eating should be focused accordingly throughout the nutrition courses’ curricula. Moreover, the data obtained from this study provide several clues to further studies to be developed regarding the still rarely approached issue of eating behaviour among nutrition students.
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