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Abstract
The role of implicit attitudes towards food and physical
activity in the treatment of youth obesity
Mietje Craeynest a,c,d , Geert Crombez a,c,d , Benedicte Deforche b,c,d ,
Ann Tanghe c,d , Ilse De Bourdeaudhuij b,c,d,⁎
a Department of Experimental Clinical and Health Psychology, Ghent University Henri Dunantlaan 2, B-9000 Ghent, Belgium
b Department of Movement and Sports Sciences, Ghent University, Watersportlaan 2, B-9000 Ghent, Belgium
c MPC Zeepreventorium, Koninklijke baan 5, B-8420 De Haan, Belgium
d Research Institute for Psychology and Health, The Netherlands
Received 11 September 2006; received in revised form 11 March 2007; accepted 16 March 2007
This study investigated whether implicit and self-reported food and exercise attitudes changed during a residential six month
treatment period in youngsters with obesity (n=19). Moreover, it was examined whether this attitudinal change explained their
decrease in overweight during the program and at a one year follow up. Two Extrinsic Affective Simon Tasks (EAST) were
conducted to investigate implicit attitudes towards exercise and food, respectively. Self-reported attitudes were assessed using a
questionnaire. The results revealed that the obese youngsters lost weight during the treatment, that was not regained at follow up.
Mean self-reported and implicit attitudes did not change markedly. Moreover, changes in self-reported attitudes were not predictive
for decrease in overweight during and after the treatment. In contrast, some small effects were found for the change in implicit
attitudes towards food and exercise. Several possible explanations are discussed.
© 2007 Elsevier Ltd. All rights reserved.
Keywords: Obesity; Implicit; Attitudes; EAST; Food; Physical activity
1. Introduction
Available online at www.sciencedirect.com
Eating Behaviors 9 (2008) 41–51
The increasing prevalence of childhood and adolescence overweight and obesity in Western society is a serious
problem (Lissau et al., 2004). It is generally acknowledged that the causal factor next to genetic predispositions is an
interplay of an unhealthy diet and a sedentary lifestyle (Morgan, Tanofsky-Kraff, Wilfley, & Yanovski, 2002).
For youngsters with severe obesity, family-based cognitive behavioural interventions that focus on increasing physical
activity and decreasing unhealthy diets are recommended (Braet, Tanghe, De Bode, Franckx, & Van Winckel, 2003). In
general, these programs have promising results. Nevertheless, a lot of youngsters regain a considerable amount of their
weight after treatment (e.g., Braet et al., 2003; Braet, Tanghe, Decaluwé, Moens, & Rosseel, 2004). Therefore, longitudinal
⁎ Corresponding author. Ghent University, Department of Movement and Sports Sciences, Watersportlaan 2, B-9000 Ghent, Belgium. Tel.: +32 9
264 63 11; fax: +32 9 264 64 84.
E-mail address: Ilse.debourdeaudhuij@UGent.be (I. De Bourdeaudhuij).
1471-0153/$ - see front matter © 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.eatbeh.2007.03.002

42 M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51
research is necessary to investigate whether the underlying dynamics of the food and physical activity behaviour are
affected by the treatment, and to what extent their change is related to weight loss and weight regain.
Several characteristics have been found to be important predictors of weight loss in obese youngsters following
treatment, under which baseline degree of overweight and the child's age (Braet, 2006). Further, an amount of theories
have dealt with possible explaining psychological determinants, such as the learning history of the child and a
heightened responsiveness to food cues (for a review, see Braet, 2005). From a healthy psychology perspective,
attitudes towards food and exercise have been put forward as crucial factors in the development and maintenance of
obesity (e.g., De Bourdeaudhuij et al., 2005; Dennison & Shepherd, 1995).
In most studies, attitudes are asked directly, for instance using self-reports. Recently, however, it has been argued
that their indirect assessment, by which cognitions are inferred from behaviour performance other than self-report,
should have a better explanatory and predictive value because of two reasons (Greenwald et al., 2002). First, indirect
measures should be more resistant for demand characteristics that often affect self-reports (see Schwarz, 1999). Second,
indirect measures are supposed to catch cognitive automatic associations that guide spontaneous behaviour, and that
can not easily be tapped by self-reports. The outcome of the indirect assessment of these associations is often called
implicit cognitions. Implicit attitudes then are the measure of automatic associations between an attitude object and a
certain valence (Greenwald et al., 2002).
In the last decades, several indirect response time based paradigms have been constructed to assess implicit attitudes
(for a review, see Fazio & Olson, 2003), amongst which the affective priming task (Fazio, Sanbonmatsu, Powell, &
Kardes, 1986), the Implicit Association Task (IAT; Greenwald, McGhee, & Schwartz, 1998) and the Extrinsic
Affective Simon Task (EAST; De Houwer, 2003). The core principle of these tasks is that implicit attitudes are inferred
from the reaction time (and percentage of errors) performance on a computer sorting task. More specifically, it is
assumed that response latencies will be shorter (and less errors will be made) when participants have to use the same
response bottom to sort stimuli that carry the same valence (congruent stimuli; e.g., names of insects and negative
nouns vs. names of flowers and positive nouns), than when the same response bottom has to be pressed for stimuli with
an opposite valence (incongruent stimuli; e.g., names of insects and positive nouns vs. names of flowers and negative
nouns). Implicit attitudes are calculated then by comparing the performance on the congruent stimuli with the
performance on the incongruent stimuli.
Indirect measures have been applied in several domains of clinical and health psychology (for a review, see Fazio &
Olson, 2003). As described elsewhere (Craeynest et al., 2005), we used the EAST in a cross-sectional study
investigating implicit food and exercise attitudes in children and adolescents with obesity at the beginning of an
intensive treatment. Our results revealed a borderline significant effect, indicating that youngsters with obesity
implicitly preferred both unhealthy and healthy food, whereas normal-weight controls evaluated them as neutral. No
effects were found for physical activity.
Longitudinal research investigating whether implicit food and physical activity cognitions in youth obesity change over
a treatment period, and to what extent they are related to treatment success (i.e., weight loss or weight gain), is scarce. We
only know of the study by Barton, Walker, Lambert, Gately, and Hill (2004) in which a sentence-completion questionnaire
was used to investigate whether automatic exercise and food cognitions change over the course of a residential weight loss
camp for adolescents with obesity. They found a reduction in negative and an increase in positive thoughts about exercise,
but not in those about eating. Further, cognitive change was largely accounted for by the reduction in weight.
This manuscript describes a longitudinal study in which implicit and self-reported food and exercise attitudes are
assessed in youngsters with obesity during a six month inpatient treatment and at a one year follow up. Self-reported
attitudes are assessed with a questionnaire; implicit attitudes are assessed with an EAST. Three main questions are
addressed: First, do implicit and self-reported food and exercise attitudes change during an inpatient treatment for obesity?
Second, to what extent does a change in these attitudes explain the variance in weight change during treatment? And third,
to what extent does a change in these attitudes explain the variance in weight loss or regain at follow up?
2. Methods
2.1. Participants
Participants were thirty-eight obese children and adolescents at the beginning of their hospitalization in 2002–2003
in a medical-paediatric centre (MPC) that is specialized in the treatment of youth obesity. Fourteen of them dropped out

during the therapy because of having reached their therapy goal (n =4) or because of suspension due to behavioural
problems breaking the rules of the centre such as smoking (n=10). Five could not be contacted at follow up. These
youngsters did not differ from the rest of the group in terms of gender, χ 2 b1, and baseline overweight, tb1. Both
groups differed in age, t(36) =2.12, p b.05: The mean age of the dropout group was higher (M=14.53, SD=2.37) than
the mean age of the study group. Data were analyzed on this restricted group of nineteen youngsters, representing 50%
of the original sample that was tested in Craeynest et al. (2005). According to Cole, Bellizzi, Flegal, and Dietz (2000),
all of them could be categorized as severely obese (mean ABMI 1 = 163.86, SD=14.97; 7 boys; age M=12.79,
SD=2.68; range 9–18 yo).
2.2. Treatment program
The treatment consisted of a maximum twelve-month multi-component inpatient program. The duration of the
treatment depended on the individual therapy goal of each participant. Every week and half of the school holidays, the
youngsters returned home. The program focused on attaining a healthy lifestyle by increasing physical activity and offering
a healthy diet within a cognitive behavioural framework. For an extensive description of the program, we refer to Braet et
al. (2003). In short, concerning physical activity, all children received an individual physical training program for 4 h a
week, including swimming, biking and fitness. Before and after school they were stimulated to participate for at least 2 h a
day in active games and lifestyle activities. During the weekends and the holidays they spent at home, they noted how
much they were physical active, using a diary. Provided that a stringent calorie restriction is not recommended for
youngsters that are still growing, the diet contained between 1500 and 1800 kcal/day. More specifically, it consisted of
three meals and three snacks per day. The consumption of soft drinks, sweets and high-calorie food was strictly regulated,
but not completely banned. Further, the psychological counselling consisted of a twelve-week cognitive behavioural
treatment program in small groups, followed by weekly individual problem-solving-based booster sessions. In order to
change their lifestyle, the youngsters were taught self-modulating skills, such as self-regulation (e.g., self-observation and
self-instruction), self-evaluation, and self-reward. Finally, the program also involved the parents. Theywereprovided
information in how the lifestyle of their child could change within the family.
2.3. Materials
2.3.1. Extrinsic Affective Simon Task
Participants conducted two EASTs: One task was related to physical activity, and one related to food. An EAST
assessing attitudes consists of attribute stimuli (words carrying a clear valence) and target stimuli (stimuli of which the
attitudes are assessed). Individually selected attractive food and physical activity words were used for the attribute
stimuli. In the physical activity EAST, targets were nine pre-selected words related to physical activity, divided into
three categories: sedentary activities (e.g., watching television), moderate intense activities (e.g., swimming) and high
intense activities (e.g., exercising). In the food EAST, targets were pre-selected words related to food, divided into two
categories: unhealthy food (e.g., French fries) and healthy food (e.g., apple). All target stimuli words are presented in
the Appendix. For a more extended description of the EASTs, we refer to Craeynest et al. (2005).
2.3.2. Self-reports
Participants had to rate the valence of the food and physical activity target stimuli words of the EASTs on a 7-point
rating scale, ranging from ‘dislike’ (−3) to ‘like’ (+3).
2.4. Procedure
M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51
This study was approved by the Ethical committee of Ghent University. To investigate their change over the
treatment period, participants were tested three times: at baseline (during the first three weeks of the treatment; T1),
1 The Body Mass Index (BMI; weight/height 2 ; kg/m 2 ) is accepted as a reliable and valid index of relative adiposity. However, as mean normal
values of BMI vary substantially with age and values for individuals of different ages are difficult to compare, an adjusted BMI (ABMI) was used.
ABMI was calculated using the formula (actual BMI/ideal BMI [50th percentile for same sex and age])×100 (Valverde, Patin, Oliveira, Lopez, &
Vitolo, 1998). The 50th percentiles were derived from Flemish growth reference charts. An ABMI of 100% is considered ideal.
43

44 M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51
six months later (T2), and at follow up one year after completing the program (T3). Concerning T2, the participants
were not exactly tested at the end of their treatment, as this moment was different for each of them. Each time, height,
weight, implicit and self-reported attitudes were assessed. For practical reasons, the first measurement was completed
at the Department of Moving and Sports Science of Ghent University, whereas the second measurement was completed
in the residential setting. For the one year follow up, the children were invited to the residential setting for a general
check-up. Sixteen youngsters of the test group showed up. The other three were tested at home.
All children were tested individually. The order in which the two EASTs were administered, was counterbalanced.
The questionnaire was completed after both EASTs were conducted. Each EAST consisted of three different blocks.
Before each task, the participant provided words for physical activities or foods that he/she really (dis)liked. Next, in a
first practice block, these individually selected attribute words appeared randomly four times in a white colour on the
screen. Participants were instructed to classify these words according to their valence as quickly and as accurately as
possible, by pressing the m-(positive) or the q-(negative) key of an AZERTY keyboard, in order to learn an extrinsic
association between a positive (negative) valence, and the left (right) key. In a second practice block, each target
stimulus was presented in at least once in blue and once in green. In the food task 12 trials were presented, and in the
activity task 24 trials. Half of the participants pressed the m-key in response to green words and the q-key in response to
blue words; the others pressed the m-key in response to blue words and the q-key in response to green words. In this
way, they learned an association between a key carrying a valence and a colour. Finally, each task consisted of four
crucial test blocks in which a mix of target and attribute words were presented. The physical activity task contained four
test blocks of 32 trials (14 white trials, 18 coloured trials) each; the food task contained four test blocks of 38 trials each
(14 white trials and 24 coloured trials). The words had to be classified depending on valence (for white words) or colour
(for green and blue words). Stimuli were always presented in a random order, whereby the mixed blocks did not
necessarily alternate between target (coloured) and attribute (white) stimuli. The inter-trial interval was 400 ms. If the
participant responded incorrectly, a red cross appeared for 400 ms on the screen and the next stimulus was presented.
2.5. Statistical analyses
Analyses were carried out using SPSS 12.0 for Windows. The analyses of the EASTs took only the responses on the
coloured test trials into account, whereby trials with an incorrect response were discarded (De Houwer, 2003). In line
with Greenwald et al. (1998), reaction times (RTs) below 300 ms or above 3000 ms were recoded to 300 ms and
3000 ms respectively. All RTs were log-transformed. Also mean percentage of errors (PE) were analysed. On the selfreports,
attitudes towards sedentary activities, moderate intense physical activity (PA), high intense PA, unhealthy food
and healthy food were obtained by averaging the respective item scores. Evolutions in mean attitudes were calculated
conducting Repeated Measures ANOVA's. The explaining variance of attitudinal changes during treatment for the
decrease in overweight during treatment and at follow up was analyzed using covariate multiple regression analyses.
3. Results
3.1. Mean implicit and self-reported attitudes at baseline
A 3 (word category: sedentary activities vs. moderate intense PA vs. high intense PA)×2 (extrinsic response
valence: positive vs. negative) Repeated Measures ANOVA on the baseline reaction times of the physical activity task
showed no significant effects, all Fsb2.85. Also the same 3×2 Repeated Measures ANOVA conducted on the baseline
percentage of errors revealed no effects, all Fsb2.19. However, a 2 (word category: unhealthy vs. healthy food) ×2
(extrinsic response valence: positive vs. negative) Repeated Measures ANOVA on the baseline reaction times of the
food task showed a significant main effect of valence, F(1, 18)=6.08, pb.05. This indicates that the participants were
positive towards both healthy and unhealthy food, which was also found in the total group as described in Craeynest
et al. (2005). No other effects were found, all Fsb1. Also the same 2 ×2 Repeated Measure ANOVA conducted on the
percentage of errors, revealed no effects, all Fsb2.49. A three-level within factor (word category: sedentary activities
vs. moderate intense vs. high intense PA) Repeated Measures ANOVA on the self-reported attitudes towards physical
activity, showed a significant effect, F(2, 17)=5.54, pb.05. Post hoc paired sample t-tests showed that moderate
intense PA was rated more positive than sedentary activities, t(18) =3.08, pb.01, and high intense PA, t(18) =2.61,
pb.05. A two-level within factor (word category: unhealthy vs. healthy food) Repeated Measures ANOVA on the

Table 1
Mean and standardized (SD) reaction times (RT) and percentage of errors (PE) on physical activity (PA) and food trials as a function of word category
and extrinsic response valence, at baseline (T1), after six months (T2) and at a one year follow up (T3)
T1 T2 T3
RT PE RT PE RT PE
M SD M SD M SD M SD M SD M SD
Physical activity (PA)
Sedentary+pos 861 229 7.89 8.09 716 127 6.14 6.11 638 110 10.09 10.96
Sedentary+neg 855 213 7.39 7.29 714 106 7.89 8.09 688 120 8.33 11.79
Moderate intense PA+pos 880 272 7.02 8.46 743 224 8.77 15.33 706 135 10.09 16.80
Moderate intense PA+neg 902 263 10.53 9.56 742 155 8.77 8.99 658 148 7.46 12.39
High intense PA+pos 814 207 8.77 8.55 746 217 12.72 14.27 679 167 7.89 8.99
High intense PA+neg
Food
833 179 6.58 8.60 736 160 7.46 13.86 676 134 7.46 16.87
Unhealthy food+positive 843 255 8.96 8.37 737 172 9.65 7.49 685 105 8.33 8.33
Unhealthy food+negative 893 277 7.67 9.35 717 178 8.77 8.20 686 86 8.11 9.57
Healthy food+positive 841 261 7.67 8.85 707 168 9.65 9.11 687 150 7.02 7.49
Healthy food+negative 898 277 9.91 8.00 734 173 9.43 6.49 717 97 8.55 11.49
self-reported attitudes towards food, showed a significant effect, F(1, 18)=4.47, pb.05. A post hoc paired t-test
revealed that the participants were more positive towards healthy food than towards unhealthy food, t(18)=2.12,
pb.05. Implicit associations are presented in Table 1; self-reported attitudes are described in Table 2.
Remarkably, the same Repeated Measures ANOVAs with the dropout participants vs. the remaining group included as
between variable, revealed a significant main effect of group on the PA EAST, F(1, 36)=5.27, pb.05, and on the food
EAST, F(1, 36)=6.25, pb.05, showing that the dropout group in general reacted faster than the remaining group (PA task
respectively M=783 ms, SD=44 ms and M=843 ms, SD=51 ms; food task respectively and M=790 ms, SD=37 ms and
M=831 ms, SD=44 ms), possibly due to the mean older age of the drop out group. Further, both groups did not differ on
the self-report attitudes towards PA, all Fsb1, however, an intriguing interaction effect was found between both groups
and their self-reported attitudes towards food, F(1, 36)=4.87, pb.05, indicating that at baseline the dropout group was
more positive towards unhealthy food and less positive towards healthy food, than the remaining group.
3.2. Mean effect of the treatment on ABMI
M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51
The mean total treatment time of the participants was almost eight months (M=7.89, SD=2.05). A Repeated
Measures ANOVA with one three-level within factor (T1 vs. T2 vs. T3), showed a significant effect of time on ABMI,
F(2, 17)=98.98, pb.001 (respectively T1: M=163.86, SD=14.97; T2: M=127.46, SD= 12.15; T3: M=130.21,
SD= 16.43). Post hoc paired sample t-tests showed that the ABMI at baseline differed significantly from the ABMI at
the end of the treatment, t(18) =13.50, pb.001, whereas the ABMI at the end of the treatment differed not from the
ABMI at follow up, t(18)=1.07, ns. This indicated that the group of participants included in the present study became
less overweight during the treatment, and that this decrease in overweight was maintained at follow up.
Table 2
Mean and standardized (SD) self-reported attitudes towards different kinds of physical activity and food, evaluated on a scale ranging from −3to+3,
at baseline (T1), after six months (T2) and at a one year follow up (T3)
T1 T2 T3
M SD M SD M SD
Physical activity (PA)
Sedentary activities 1.34 0.99 1.70 0.97 2.00 0.54
Moderate intense PA 2.04 1.06 2.07 1.01 2.16 0.80
High intense PA
Food
1.02 1.09 1.67 1.02 1.88 0.80
Unhealthy food 0.96 1.86 0.72 1.82 0.69 1.20
Healthy food 2.07 0.80 1.89 0.97 1.91 1.24
45

46 M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51
3.3. Mean evolution in implicit and self-reported attitudes during treatment
3.3.1. Implicit attitudes
Physical activity. A 3 (time: T1 vs. T2 vs. T3) ×3 (word category: sedentary activities vs. moderate intense PA vs.
high intense PA) ×2 (extrinsic response valence: positive vs. negative) Repeated Measures ANOVA only revealed a
main effect of time on the reaction times, F(2, 17)=10.22, pb.01, indicating that the participants reacted faster on the
persecuting test moments (respectively T1: M=858 ms, SD=47 ms; T2: M=733 ms, SD=34 ms; T3: M=674 ms,
SD=29 ms). No effects were found for word category, all Fsb1.82, and extrinsic response valence, all Fsb2.56. This
indicated that the participants remained neutral towards sedentary activities, moderate and intense PA. The same
3×3×2 ANOVA performed on the percentages of errors, showed no significant effects, all Fsb1.35.
Food. Using a 3 (time: T1 vs. T2 vs. T3)×2 (word category: unhealthy vs. healthy food) ×2 (extrinsic response
valence: positive vs. negative) Repeated Measures ANOVA, the results only revealed a main effect for time, F(2, 17)=
416.88, pb.001. This indicated that the participants react faster on the persecuting test moments (respectively T1:
M=868 ms, SD=59 ms; T2: M=724 ms, SD=38 ms; T3: M=694 ms, SD=23 ms). No effects were found for word
category and extrinsic response valence, all Fsb3.23. The same 4×2×2 ANOVA was conducted on the percentages of
errors, however no significant effects were found, all Fsb2.10. Implicit food and physical activity associations are
presented in Table 1.
3.3.2. Self-reported attitudes
Physical activity. A 3 (time: T1 vs. T2 vs. T3)×3 (word category: sedentary activities vs. moderate intense vs. high
intense PA) Repeated Measures ANOVA showed a main effect of time, F(2, 17)=5.93, pb.05, indicating that the
participants became more positive on the successive measure moments (T1: M=1.47, SD=0.14; T2: M=1.81,
SD=0.14; T3: M=2.01, SD=0.11). Also the main effect of word category was significant, F(2, 17)=8.16, pb.01.
Post hoc paired t-tests revealed that in general, moderate intense PA (M=2.09, SD=0.50) was rated more positive than
sedentary activities (M=1.68, SD=0.40), t(18) =3.59, pb.01, and than high intense PA (M=1.52, SD=0.77), t(18) =
2.78, p b.05. Sedentary activities and high intense PA were rated equally, tb1. The interaction effect of time and word
category was not significant, Fb1.
Food. A 3 (time: T1 vs. T2 vs. T3) ×2 (word category: unhealthy vs. healthy food) ANOVAwith Repeated Measures
showed a main effect of word category, F(1, 17)=6.46, pb.05. A post hoc paired t-test revealed that, in general, the
participants were more positive towards healthy (M=1.97, SD=0.69) than towards unhealthy food (M=0.91,
SD=1.51), t(18)=2.38, pb.05. The main effect of time and the interaction effect of time and word category were not
significant, both Fsb1. Table 2 describes the mean self-reported attitudes for the persecuting test moments.
3.4. Prediction of ABMI change during treatment by attitudinal change during treatment
To investigate whether attitudinal changes could explain the variance in ABMI change, we conducted standard
multiple regression analyses. Because of the small sample size, the predictive power of the several attitudinal change
variables on ABMI change was examined separately for implicit and self-reported attitudes and for food and physical
activity, resulting in four different models. In each model, baseline ABMI, age and sex (entered as a dummy variable:
girl=0; boy=1) were entered as covariates. ABMI and attitudinal change during treatment were calculated by
respectively subtracting the ABMI and attitudinal scores at T1 from T2.
3.4.1. Implicit attitudes towards physical activity
In a first model, ABMI change during treatment was the dependent variable, and the change in attitude towards
sedentary activity (RT), towards moderate intense PA (RT), towards high intense PA (RT), towards sedentary activity
(PE), towards moderate intense PA (PE), towards high intense PA (PE), baseline ABMI, age and sex were entered as
independent variables. The model accounted for 73% of the variance, F(9, 18)=6.51, pb.01. Attitudinal change
towards high intense PA (RT) was a significant predictor, adjusted for age, sex and baseline ABMI, β=.51; t(18) =2.91,
pb.05. Remarkably, this indicated that a decrease in overweight was related to a more negative attitude towards high
intense PA at the end of the treatment. Further, also baseline ABMI, β = −.57; t(18)=4.03, p b.01, and sex, β =.64;
t(18)=4.12, p b.01, were significant predictors. The first indicated that decrease in overweight was related to a
higher baseline ABMI, and the latter indicated that girls had a higher probability to decrease in overweight than

Table 3
Regression analyses predicting AMBI change during treatment from implicit attitudinal change towards PA and food during treatment
Adj.
R 2
boys. Age was a marginal significant predictor, β =.35; t(18)=2.14, p =.06, indicating that decrease in overweight
was related to a younger age (see Table 3).
3.4.2. Implicit attitudes towards food
In a second model, ABMI change during treatment was the dependent variable, and the change in attitude towards
unhealthy food (RT), towards healthy food (RT), towards unhealthy food (PE), towards healthy food (PE), baseline
ABMI, age and sex were entered as independent variables. The model accounted for 69% of the variance, F(7, 18)=
6.75, pb.01. Attitudinal change towards healthy food (PE), was a significant predictor, β=.39; t(18)=2.49, pb.05,
indicating that decrease in overweight was related to a more positive attitude towards healthy food at the end of
the treatment, adjusted for age, sex and baseline ABMI. Further, again baseline ABMI, β=−.62; t(18) =4.59, pb.01,
and sex, β =.49; t(18)=3.62, p b.01, were significant predictors, and age was a marginal significant predictor,
β =.30; t(18)=2.07, p =.06 (see Table 3).
3.4.3. Self-reported attitudes towards physical activity.
In a third model, ABMI change during treatment was the dependent variable, and the change in attitude towards
sedentary activity, towards moderate intense PA, towards high intense PA, baseline ABMI, age and sex were entered as
independent variables. The model accounted for 49% of the variance, F(6, 18)=3.88, pb.05. Only baseline ABMI
and sex were significant predictors, respectively β=−.64; t(18) =3.06, pb.05 and β=.49; t(18) =2.65, pb.05 (see
Table 4).
Table 4
Regression analyses predicting AMBI change during treatment from self-reported attitudinal change towards PA and food during treatment
Adj.
R 2
Significant
correlates
M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51
Significant correlates Standard coefficient
beta
Standard coefficient
beta
Adj.
R 2
Significant
correlates
PA Food
Total model: .49 Total model: .61
F(6, 18)=3.88⁎ F(5, 18)= 6.73⁎⁎
Sex .49⁎ Sex .53⁎⁎
Age .21 Age .30
Baseline ABMI −.64⁎ Baseline ABMI −.72⁎⁎
Sedentary activity −.03 Unhealthy food .17
Mod. intense PA .09 Healthy food .30
High intense PA −.02
⁎pb.05; ⁎⁎pb.01.
Adj.
R 2
Significant
correlates
PA Food
Total model: .73 Total model: .69
F(9, 18)=6.51⁎⁎ F(7, 18)=6.75⁎⁎
Sex .64⁎⁎ Sex .49⁎⁎
Age .35 Age .30
Baseline ABMI −.57⁎⁎ Baseline ABMI −.62⁎⁎
Sedentary activity (RT) −.02 Unhealthy food (RT) −.14
Mod. intense PA (RT) −.26 Healthy food (RT) −.03
High intense PA (RT) .51⁎
Sedentary activity (PE) .06 Unhealthy food (PE) −.01
Mod. intense PA (PE) −.06 Healthy food (PE) .39⁎
High intense PA (PE) .13
⁎ pb.05; ⁎⁎ pb.01.
47
Standard coefficient
beta
Standard coefficient
beta

48 M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51
Table 5
Regression analyses predicting AMBI change at follow up from implicit attitudinal change towards PA and food during treatment
Adj.
R 2
Significant
correlates
Standard coefficient
beta
3.4.4. Self-reported attitudes towards food
In a fourth model, ABMI change during treatment was the dependent variable, and the change in attitude towards
unhealthy food, towards healthy food, baseline ABMI, age and sex were entered as independent variables. The model
accounted for 61% of the variance, F(5, 18)=6.73, pb.01. Only baseline ABMI and sex were significant predictors,
respectively β=−.72; t(18) =4.44, pb.01 and β=.53; t(18) =3.35, pb.01 (see Table 4).
3.5. Prediction of ABMI change at follow up by attitudinal change during treatment
To investigate whether attitudinal changes could explain the variance in ABMI change at follow up, we conducted
standard multiple regression analyses in again four separate models. ABMI change at follow up was calculated by
subtracting the ABMI at T2 from the ABMI at T3; attitudinal changes during treatment were calculated by subtracting
the attitudinal scores at T1 from the attitudinal scores at T2.
3.5.1. Implicit attitudes towards physical activity
In a first model, ABMI change at follow up was the dependent variable, and the change in attitude towards sedentary
activity (RT), towards moderate intense PA (RT), towards high intense PA (RT), towards sedentary activity (PE),
towards moderate intense PA (PE), towards high intense PA (PE), ABMI at the end of the treatment, age and sex were
entered as independent variables. The model accounted for 40% of the variance, but was not significant, F(9, 18)=
2.32 ns. Only the change in implicit attitude towards moderate PA (RT) was a significant predictor, β=.89;t(18) =2.78,
pb.05, indicating that decrease in overweight at follow up is related to a change towards a negative implicit attitude
towards moderate intense physical activity at the end of the treatment, adjusted for age, sex and ABMI (see Table 5).
Adj.
R 2
Significant
correlates
PA Food
Total model: .40 Total model .08
F(9, 18)=2.32 F(7, 18)=1.22
Sex −.34 Sex .29
Age .37 Age .42
Baseline ABMI .13 Baseline ABMI −.37
Sedentary activity (RT) −.03 Unhealthy food (RT) .48
Mod. intense PA (RT) .89⁎ Healthy food (RT) .02
High intense PA (RT) .12
Sedentary activity (PE) .15 Unhealthy food (PE) .23
Mod. intense PA (PE) −.33 Healthy food (PE) .05
High intense PA (PE) −.05
⁎pb.05.
Table 6
Regression analyses predicting AMBI change at follow up from self-reported attitudinal change towards PA and food during treatment
Adj.
R 2
Significant
correlates
Standard coefficient
beta
Adj.
R 2
Significant
correlates
PA Food
Total model: .03 Total model: .14
F(6, 18)=1.10 F(5, 18)=0.57
Sex .08 Sex .20
Age .53 Age .43
Baseline ABMI −.30 Baseline ABMI −.31
Sedentary activity −.59 Unhealthy food −.13
Mod. intense PA .53 Healthy food .28
High intense PA .20
Standard coefficient
beta
Standard coefficient
beta

3.5.2. Implicit attitudes towards food
In a second model, ABMI change at follow up was the dependent variable, and the change in attitude towards
unhealthy food (RT), towards healthy food (RT), towards unhealthy food (PE), towards healthy food (PE), ABMI at the
end of the treatment, age and sex were entered as independent variables. The model accounted for only 8% of the
variance, and was not significant, F(7, 18)=1.22 ns (see Table 5).
3.5.3. Self-reported attitudes towards physical activity
In a third model, ABMI change at follow up was the dependent variable, and the change in attitude towards
sedentary activity, towards moderate intense PA, towards high intense PA, ABMI at the end of the treatment, age and
sex were entered as independent variables. The model accounted for only 3% of the variance, and was not significant, F
(6, 18)=1.10 ns. (see Table 6).
3.5.4. Self-reported attitudes towards food
In a fourth model, ABMI change at follow up was the dependent variable, and the change in attitude towards
unhealthy food, towards healthy food, ABMI at the end of the treatment, age and sex were entered as independent
variables. The model accounted for 14% of the variance, and was not significant, F(5, 18)b1 (see Table 6).
4. Discussion
M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51
This manuscript presented a longitudinal study, investigating whether implicit and self-reported food and
exercise attitudes changed during a six month inpatient treatment for youth obesity and at a one year follow up.
Further, it was examined whether this change explained the variance in overweight change during treatment and at
follow up.
A first finding was that the youngsters lost weight during the treatment, that seemed not to be regained at follow up.
This lack of weight regain is in contrast with what is often found (e.g., Braet et al., 2003, 2004). However, the finding of
the present study should be interpreted with caution, as it is based on a very restricted and selective sample. As the
dropout youngsters reported at baseline that they liked more unhealthy food and liked less healthy food than the
remaining group, it can be assumed that especially the youngsters that regained weight after treatment, dropped out or
could not be contacted at follow up. Another possibility may be that the participants further lost weight after the
six months of treatment that was regained at follow up.
The self-reports revealed more favourable attitudes towards healthy food and physical activity than towards
unhealthy food and sedentary activities. This pattern was quite stable over time. Further, a change in self-reported
attitudes was not related to decrease in overweight during treatment and at follow up. Possibly, demand
characteristics leading to self-presentation strategies may have played a role (see Schwarz, 1999), but this pattern
can also reflect a gap between a positive attitude towards health practices and the intention to effectively perform
health behaviour. Moreover, it should be noted that the attitudes were assessed when the treatment had already
started.
Of particular interest was the change in implicit food and physical activity attitudes during treatment, and the
relation with decrease in overweight. At baseline, the participants had positive attitudes towards both healthy and
unhealthyfood,whichwasalsofoundinthetotalgroupsampleasdescribedinCraeynest et al. (2005).However,this
mean effect disappeared in a longitudinal study design. Nevertheless, some specific changes in implicit attitude
towards food and physical activity seemed to be related to the decrease in overweight during treatment and at follow
up. More specifically, it was found that the decrease in overweight at the end of the treatment was related to
becoming more positive towards healthy food during therapy. This pattern seems in line with studies that applied the
Transtheoretical Model of behavioural change (Prochaska & DiClimente, 1983) on fruit and vegetable consumption,
which found that increasing the perception of the benefits of the consumption of fruit and vegetables is a crucial
factor for the move towards a higher behavioural stage (e.g., Cullen, Bartholomew, Parcel, & Koehly, 1998; Greene
et al., 2004). Therefore, it may be assumed that emphasizing the benefits of healthyfoodiselementaryinthe
treatment of childhood obesity. Further, a more negative attitude towards high intense physical activity and towards
moderate intense physical activity seemed to be predictive for respectively decrease in overweight at the end of the
treatment and at follow up. At first sight, these effects are not in line with the expectations. Nevertheless, they can
also indicate that the youngsters who lost much weight are fed up with being intensively physical active. However,
49

50 M. Craeynest et al. / Eating Behaviors 9 (2008) 41–51
given the fact that these effects were not found on both performance levels (reaction times and percentage of errors)
and that earlier studies did not show any evidence for implicit attitudes towards physical activity (e.g., Craeynest
et al., 2005; butseeBarton et al., 2004), the implicit attitude effects should be interpreted with caution. In contrast,
decrease in overweight seemed to be strongly related to ‘fixed’ variables such as sex, age and baseline ABMI (see
also Braet, 2006).
There are several aspects that may offer a possible explanation for the only limited and tentative implicit attitude effects we
found. First, it is obvious that the small sample size, due to the huge dropout, may have reduced the power of the analyses.
Second, the treatment took place in a very controlled setting with strict diet and exercise guidelines. Given the
accumulating evidence that the environment is an important predictor for food choice and physical activity (Booth
et al., 2001), it may be that the decrease in overweight during treatment was rather due to ‘external’ environmental
characteristics, than to ‘internalized’ psychosocial determinants such as implicit attitudes.
Third, it has been demonstrated that implicit measures may not be considered as stable constructs that are
immune for contextual influences (Blair, 2002). Therefore, it may be that the results were attenuated by the different
contexts in which the youngsters were assessed (at the medical paediatric centre, at the university, and for a minority
at home).
Fourth, as mentioned in the Introduction, there is no doubt that using indirect measures may have several advantages
over self-reports (Greenwald et al., 2002). Nevertheless, each of the paradigms has its own limitations that should be
considered. With respect to the EAST, at this moment little is known about its validity and reliability. Huijding and de
Jong (2005) found that a pictorial version of the EAST had good predictive validity for avoidance behaviour in
individuals with spider phobia. However, Teige, Schnabel, Banse, and Asendorpf (2004) found that the EAST
investigating implicit self-concept of personality had low internal consistency. Undoubtedly, more research is needed
about the psychometric characteristics of the EAST, not only in general, but also within specific domains such as in the
assessment of food and physical activity cognitions in children and adolescents. In addition, it should be investigated to
what extent the performance on indirect measures in a longitudinal study design is related to learning effects. Steffens
(2004) found that faking becomes easier after having some experience with an IAT, and probably the same is true for
the EAST.
Finally, there are some limitations that should be considered. First, the results of the treatment, both on decrease in
overweight and on attitudinal change, would have been stronger if they could be compared with those of an untreated
group of obese youngsters. Second, food and exercise attitudes are not direct determinants of weight, but they are
mediated by food intake and exercise behaviour. Therefore, future research should include objective behavioural
measures. Moreover, correlations between these behavioural and the implicit measures can provide then an idea of the
validity of the implicit measures (see Teachman & Woody, 2003).
In sum, this study showed that a decrease in overweight in obese youngsters after a six month inpatient treatment
was not significantly related to self-reported attitudes. In contrast, a decrease in overweight seemed to be related to
some changes in implicit attitudes towards food and physical activity, but these findings should be interpreted with
caution. More research is needed to the psychometric qualities of implicit measures within this field, and to what extent
implicit food and exercise attitudes are related to actual food intake and exercise behaviour.
Acknowledgements
This research was supported by grant B/03814/01 from the Ghent University. We are very grateful to the MPC
Zeepreventorium and the children for their cooperation to this study. In addition, we wish to thank Jan De Houwer for
his ideas on conceptualizing the experiment. Furthermore, many thanks go to all colleagues and students who assisted
in data collection, especially Els Persijn, Leen Van Vlierberghe, Katrien Verhoeven and Mieke De Roo.
Appendix A
Target stimuli of the EAST
Target stimuli food:
Unhealthy food words: crisps, coke, French fries
Healthy food words: water, apple, tomato

Target stimuli physical activity:
Sedentary behaviour words: reading, watching TV, resting
Moderate intense physical activity words: walking, cycling, swimming
High intense physical activity words: running, training, exercising
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